AP Biology Flashcards: Complete 8-Unit Course Review
Review all 8 AP Biology units with original flashcards for concepts, pathways, experimental design, data interpretation, and FRQ reasoning.
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AP Biology Flashcards: Complete 8-Unit Course Review
The current AP Biology framework covers eight units, from chemistry of life through ecology. This 540-card deck turns that full course into short, original retrieval prompts, with science-practice reasoning mixed into the biology instead of parked in a separate section.
What the cards practice
The cards connect terms to functions, structures to consequences, pathway steps to inputs, outputs, locations, and regulation, and evidence to biological claims. Separate prompts cover useful reverse mappings when they are real study tasks—for example, identifying a process from its location or choosing the inference supported by a result. Short original scenarios also practice describing patterns, explaining mechanisms, predicting changes, justifying claims, setting up calculations, and evaluating evidence.
The deck does not mechanically reverse every definition or pathway. It leaves out copied exam material, scoring language, official figures, exhaustive protocols, broad essay prompts, textbook-specific trivia, and advanced-college details outside the current course boundary.
Learning order
The sequence follows Units 1–8. Within each unit it moves from prerequisites to processes, applications, experiments, data, and FRQ-style reasoning, while spacing close variants apart. Long-term spacing and interleaving are left to the review scheduler.
What still needs practice
Flashcards are useful for recall and small reasoning moves, but they cannot replace laboratory work, graph construction, extended data analysis, or timed multiple-choice and free-response practice. Use the deck beside class labs and full original practice questions.
Scope and provenance
The course boundary was reviewed on September 1, 2026 against the College Board AP Biology course page, the Fall 2025 Course and Exam Description, its current clarifications and corrections, the 2026–27 course-change table, and the current exam page. The selection, prompts, answers, examples, sequence, metadata, and cover are independently created from common biological knowledge and source checks. No exam questions, scoring guidelines, CED text, answer keys, or official figures were copied or transformed.
The Common knowledge · CC0 1.0 label applies to the original wording, organization, metadata, and generated media to the extent applicable rights exist. It does not claim ownership of biological facts, AP or College Board names, or third-party source material.
This independent, unofficial study deck is not affiliated with, endorsed by, or sponsored by College Board. AP and College Board names identify the course and exam only. Official requirements: https://apcentral.collegeboard.org/courses/ap-biology
Carte in questo mazzo
Carta 1
Domanda
Why is a water molecule polar?
Risposta
Oxygen pulls shared electrons more strongly than hydrogen, giving oxygen a partial negative charge and the hydrogens partial positive charges.
Carta 2
Domanda
Which elements make up most biological molecules?
Risposta
Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur—often shortened to CHNOPS.
Carta 3
Domanda
What is the relationship between a monomer and a polymer?
Risposta
Monomers are small building blocks; polymers are chains or networks made from repeated monomers.
Carta 4
Domanda
What is a monosaccharide's main role in cells?
Risposta
It can provide quick energy and serve as a building block for larger carbohydrates.
Carta 5
Domanda
Why do lipids mix poorly with water?
Risposta
Most of their bonds are nonpolar, so water cannot form favorable interactions with them.
Carta 6
Domanda
What three parts make up a nucleotide?
Risposta
A five-carbon sugar, a phosphate group, and a nitrogenous base.
Carta 7
Domanda
What parts of an amino acid vary and stay constant?
Risposta
The amino group, carboxyl group, hydrogen, and central carbon are shared; the side chain, or R group, varies.
Carta 8
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What does pH measure?
Risposta
The negative logarithm of hydrogen-ion concentration; lower pH means more hydrogen ions.
Carta 9
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What is a hydrogen bond in liquid water?
Risposta
A weak attraction between a partially positive hydrogen on one water molecule and a partially negative oxygen on another.
Carta 10
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How does an unsaturated fatty acid differ from a saturated one?
Risposta
An unsaturated fatty acid has at least one carbon–carbon double bond; a saturated fatty acid has none.
Carta 11
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What bond links amino acids in a polypeptide?
Risposta
A peptide bond.
Carta 12
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What does dehydration synthesis do?
Risposta
It joins subunits with a covalent bond while removing the elements of water.
Carta 13
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How does cohesion help water move through a plant?
Risposta
Hydrogen bonds keep water molecules linked, helping a continuous column rise through xylem.
Carta 14
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How do plants and animals differ in short-term glucose storage?
Risposta
Plants store glucose mainly as starch; animals store it mainly as glycogen.
Carta 15
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What determines a protein's primary structure?
Risposta
Its amino-acid sequence.
Carta 16
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How does a cis double bond affect a fatty-acid tail?
Risposta
It introduces a bend that prevents neighboring tails from packing tightly.
Carta 17
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How does adhesion support water transport in narrow tubes?
Risposta
Water sticks to polar surfaces, helping it resist gravity along cell walls.
Carta 18
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Which base pairing distinguishes RNA from DNA?
Risposta
RNA uses uracil, so adenine pairs with uracil instead of thymine.
Carta 19
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What stabilizes common protein secondary structures?
Risposta
Hydrogen bonds between atoms in the polypeptide backbone.
Carta 20
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Why can carbon form so many biological structures?
Risposta
It has four valence electrons and can form four stable covalent bonds, including chains, branches, and rings.
Carta 21
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Why can some insects stand on water?
Risposta
Cohesion among surface water molecules creates high surface tension.
Carta 22
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What does hydrolysis do to a biological polymer?
Risposta
It adds the elements of water to break a covalent bond between subunits.
Carta 23
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What carbohydrate strengthens plant cell walls?
Risposta
Cellulose.
Carta 24
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Why are fats useful for long-term energy storage?
Risposta
Their many C–H bonds store substantial chemical energy, and hydrophobic storage adds little water mass.
Carta 25
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How does water buffer rapid temperature change?
Risposta
Breaking and forming many hydrogen bonds absorbs or releases substantial heat, giving water a high specific heat.
Carta 26
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What does antiparallel mean for a DNA double helix?
Risposta
Its two strands run in opposite directions: one 5′→3′ and the other 3′→5′.
Carta 27
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What mainly drives a protein's tertiary structure?
Risposta
Interactions among side chains, including hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.
Carta 28
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What is a trace element?
Risposta
An element an organism needs in very small amounts, such as iron in many electron-transfer proteins.
Carta 29
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Why does sweating cool an organism?
Risposta
The fastest water molecules escape as vapor, carrying heat away from the surface.
Carta 30
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A cell builds a polysaccharide from sugars. Is water consumed or released?
Risposta
Released. Forming each linkage by dehydration removes water.
Carta 31
Domanda
Why can branching help a storage polysaccharide release glucose quickly?
Risposta
More branch ends give enzymes more sites to work at once.
Carta 32
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What makes a phospholipid amphipathic?
Risposta
It has a polar, hydrophilic head and nonpolar, hydrophobic tails.
Carta 33
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Where is biological information encoded in a nucleic acid?
Risposta
In the linear sequence of nucleotide bases.
Carta 34
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What is quaternary protein structure?
Risposta
The arrangement of two or more polypeptide subunits into one functional protein.
Carta 35
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Why does ice float on liquid water?
Risposta
Stable hydrogen bonds hold ice molecules in an open lattice, making ice less dense than liquid water.
Carta 36
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How does electronegativity affect a covalent bond?
Risposta
A difference in attraction for electrons makes electron sharing unequal and can create a polar bond.
Carta 37
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A digestive reaction adds water while splitting a macromolecule. What reaction is this?
Risposta
Hydrolysis.
Carta 38
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What links monosaccharides in a polysaccharide?
Risposta
Glycosidic covalent bonds.
Carta 39
Domanda
Why do phospholipids form bilayers in water?
Risposta
Hydrophilic heads face water while hydrophobic tails cluster away from it.
Carta 40
Domanda
To which end are nucleotides added during nucleic-acid synthesis?
Risposta
The 3′ end of the growing strand.
Carta 41
Domanda
Why can one amino-acid substitution change protein function?
Risposta
It can alter side-chain interactions, folding, stability, or an active or binding site.
Carta 42
Domanda
How does a buffer resist a pH change?
Risposta
It can accept added hydrogen ions or donate them when hydrogen-ion concentration falls.
Carta 43
Domanda
Why is water a useful solvent for cells?
Risposta
Its partial charges surround ions and other polar molecules, separating and dispersing them.
Carta 44
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Why do functional groups matter in organic molecules?
Risposta
They give carbon skeletons predictable chemical properties, such as polarity, acidity, or reactivity.
Carta 45
Domanda
Why can two polymers built from similar monomers have different functions?
Risposta
Their monomer sequence, branching, length, and three-dimensional shape can differ.
Carta 46
Domanda
A seedling consumes stored starch. What happens to the starch?
Risposta
Hydrolysis breaks it into smaller sugars that can enter energy pathways.
Carta 47
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What are two biological roles of steroids?
Risposta
Some act as signaling molecules, and cholesterol helps stabilize animal cell membranes.
Carta 48
Domanda
What bond forms the backbone of a nucleic-acid strand?
Risposta
Covalent phosphodiester bonds link the sugar of one nucleotide to the phosphate of the next.
Carta 49
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What does denaturation do to a protein?
Risposta
It disrupts the protein's three-dimensional shape and often its function without usually breaking the primary peptide chain.
Carta 50
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An enzyme works best near pH 7 but slows at pH 3. What is a likely explanation?
Risposta
Extra hydrogen ions changed charges and interactions that maintain the enzyme's active shape.
Carta 51
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What structure encloses every cell?
Risposta
A plasma membrane.
Carta 52
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What is the nucleus's main function?
Risposta
It houses most eukaryotic DNA and is a major site of DNA replication and transcription.
Carta 53
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Why does surface-area-to-volume ratio fall as a cell grows?
Risposta
Volume increases with the cube of length, while surface area increases with the square.
Carta 54
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What does the fluid mosaic model describe?
Risposta
A dynamic phospholipid bilayer containing mobile proteins, sterols, and carbohydrates.
Carta 55
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What drives simple diffusion?
Risposta
Random molecular motion produces net movement from higher to lower concentration.
Carta 56
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How does active transport differ from facilitated diffusion?
Risposta
Active transport moves a substance against its gradient using energy; facilitated diffusion moves it down a gradient.
Carta 57
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Why does compartmentalization increase cellular efficiency?
Risposta
It concentrates enzymes and substrates and maintains distinct conditions for different reactions.
Carta 58
Domanda
When should a light microscope be preferred over an electron microscope?
Risposta
When observing living cells or dynamic processes at lower resolution.
Carta 59
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What does the nucleolus produce?
Risposta
Ribosomal RNA and early ribosome subunits.
Carta 60
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Does passive transport require direct cellular energy?
Risposta
No. It moves substances down an electrochemical or concentration gradient.
Carta 61
Domanda
What feature separates prokaryotic from eukaryotic cells?
Risposta
Eukaryotic cells have a membrane-bound nucleus and other membrane-bound organelles; prokaryotic cells do not.
Carta 62
Domanda
Which membrane region blocks most ions and polar molecules?
Risposta
The hydrophobic interior formed by phospholipid tails.
Carta 63
Domanda
What happens on rough endoplasmic reticulum?
Risposta
Bound ribosomes make proteins for secretion, membranes, or the endomembrane system.
Carta 64
Domanda
How does facilitated diffusion differ from simple diffusion?
Risposta
It uses a channel or carrier protein but still moves a substance down its gradient.
Carta 65
Domanda
Where is prokaryotic DNA usually located?
Risposta
In a nucleoid region rather than inside a membrane-bound nucleus.
Carta 66
Domanda
How does cholesterol affect an animal membrane?
Risposta
It buffers fluidity, limiting excess movement when warm and preventing tight packing when cool.
Carta 67
Domanda
What does smooth endoplasmic reticulum do?
Risposta
It synthesizes lipids, detoxifies some compounds, and stores calcium in specialized cells.
Carta 68
Domanda
What determines a channel protein's selectivity?
Risposta
Its pore size, shape, charge, and gating behavior.
Carta 69
Domanda
What does the sodium–potassium pump accomplish?
Risposta
Using ATP, it exports three sodium ions and imports two potassium ions per cycle.
Carta 70
Domanda
What do ribosomes do in both prokaryotic and eukaryotic cells?
Risposta
They translate mRNA into polypeptides.
Carta 71
Domanda
What is the Golgi apparatus's role?
Risposta
It modifies, sorts, and packages proteins and lipids arriving from the endoplasmic reticulum.
Carta 72
Domanda
What is osmosis?
Risposta
Net movement of water across a selectively permeable membrane toward lower free-water concentration.
Carta 73
Domanda
Why does a high surface-area-to-volume ratio help a cell?
Risposta
It provides more membrane area per unit of cytoplasm for exchange with the environment.
Carta 74
Domanda
How do unsaturated phospholipid tails affect membrane fluidity?
Risposta
Their bends reduce tight packing, usually increasing fluidity.
Carta 75
Domanda
Trace a secreted protein after translation begins.
Risposta
Rough ER → transport vesicle → Golgi → secretory vesicle → plasma membrane.
Carta 76
Domanda
What happens to an animal cell in a hypotonic solution?
Risposta
Water enters; the cell swells and may lyse.
Carta 77
Domanda
What is cotransport?
Risposta
The downhill movement of one substance powers the uphill transport of another through the same protein.
Carta 78
Domanda
What is the main role of a cell wall?
Risposta
It provides structural support and helps prevent excessive expansion.
Carta 79
Domanda
What do lysosomes do?
Risposta
Their hydrolytic enzymes digest macromolecules and recycle damaged cell parts in an acidic compartment.
Carta 80
Domanda
What happens to an animal cell in a hypertonic solution?
Risposta
Water leaves; the cell shrinks.
Carta 81
Domanda
How do intestinal microvilli improve absorption?
Risposta
They increase membrane surface area without greatly increasing cell volume.
Carta 82
Domanda
What can an integral membrane protein do?
Risposta
It can transport substances, receive signals, catalyze reactions, or anchor cell structures.
Carta 83
Domanda
What is a central vacuole's major role in a plant cell?
Risposta
It stores solutes and water and helps maintain turgor pressure.
Carta 84
Domanda
What happens to a plant cell in a hypotonic solution?
Risposta
Water enters and turgor pressure rises; the cell wall helps prevent bursting.
Carta 85
Domanda
How can a proton gradient power sucrose uptake in a plant cell?
Risposta
Protons flow down their gradient through a symporter that carries sucrose uphill.
Carta 86
Domanda
What evidence supports the endosymbiotic origin of mitochondria?
Risposta
They have double membranes, circular DNA, bacterial-like ribosomes, and divide independently by a similar process.
Carta 87
Domanda
Which overall energy-conversion pathway mainly occurs in mitochondria?
Risposta
Most stages of aerobic cellular respiration and ATP production.
Carta 88
Domanda
What happens to a plant cell in a hypertonic solution?
Risposta
Water leaves, turgor falls, and the membrane may pull from the wall during plasmolysis.
Carta 89
Domanda
Why can't a standard light microscope resolve a ribosome clearly?
Risposta
A ribosome is smaller than the microscope's diffraction-limited resolution.
Carta 90
Domanda
How do bacterial and plant cell walls differ?
Risposta
Bacterial walls usually contain peptidoglycan; plant walls contain cellulose.
Carta 91
Domanda
Which overall energy-conversion pathway occurs in chloroplasts?
Risposta
Photosynthesis: converting light energy into chemical energy and fixing carbon.
Carta 92
Domanda
A cubical cell doubles each side length. How do surface area and volume change?
Risposta
Surface area increases 4-fold; volume increases 8-fold.
Carta 93
Domanda
What is the role of membrane carbohydrates?
Risposta
They help cells recognize and interact with one another.
Carta 94
Domanda
What is water potential?
Risposta
A measure predicting water movement; water moves from higher to lower water potential.
Carta 95
Domanda
How do microtubules support a cell?
Risposta
They resist compression, form tracks for motors, and build structures such as spindles, cilia, and flagella.
Carta 96
Domanda
What is endocytosis?
Risposta
The plasma membrane folds inward to bring material into the cell in a vesicle.
Carta 97
Domanda
What evidence supports the endosymbiotic origin of chloroplasts?
Risposta
They share bacterial-like DNA, ribosomes, division, and a double membrane consistent with engulfment.
Carta 98
Domanda
In a membrane-permeability test, what is the independent variable?
Risposta
The factor deliberately changed, such as temperature or solute identity.
Carta 99
Domanda
How do microfilaments support cell movement?
Risposta
Actin filaments interact with motor proteins to change cell shape, contract, and move materials.
Carta 100
Domanda
What does the cytosol contain?
Risposta
Water, ions, small molecules, and proteins where many metabolic reactions occur.
Carta 101
Domanda
Why can diffusion limit cell size?
Risposta
As dimensions grow, molecules must travel farther, while exchange area does not keep pace with metabolic volume.
Carta 102
Domanda
What does selective permeability mean?
Risposta
The membrane allows some substances to cross more readily than others.
Carta 103
Domanda
What is an intermediate filament's general role?
Risposta
It provides durable mechanical strength and helps anchor structures.
Carta 104
Domanda
How does adding a nonpenetrating solute affect water potential?
Risposta
It makes solute potential, and usually total water potential, more negative.
Carta 105
Domanda
What is exocytosis?
Risposta
A vesicle fuses with the plasma membrane and releases contents outside the cell.
Carta 106
Domanda
Why can lysosomal enzymes digest safely inside a cell?
Risposta
A membrane isolates the acidic enzymes from most cytosolic components.
Carta 107
Domanda
Why include an untreated membrane sample in an experiment?
Risposta
It provides a control baseline for judging the treatment's effect.
Carta 108
Domanda
Why doesn't cell size alone identify whether a cell is prokaryotic?
Risposta
Sizes overlap; the presence or absence of internal membrane-bound structures is stronger evidence.
Carta 109
Domanda
Why are organelle interactions important?
Risposta
Cell functions often require products to move through several specialized compartments rather than one organelle working alone.
Carta 110
Domanda
What graph would show a size constraint clearly?
Risposta
Plot cell size on the x-axis and surface-area-to-volume ratio on the y-axis; the ratio should decline as size rises.
Carta 111
Domanda
Which molecules cross a phospholipid bilayer most easily without proteins?
Risposta
Small nonpolar molecules, such as oxygen and carbon dioxide.
Carta 112
Domanda
Two solutions have equal water potential. What is the net water movement?
Risposta
None, although water molecules still move both ways.
Carta 113
Domanda
Why is ATP loss likely to disrupt ion balance?
Risposta
ATP-powered pumps stop maintaining gradients, so passive leaks move ions toward equilibrium.
Carta 114
Domanda
How does folding an internal membrane help an organelle?
Risposta
It increases surface area for membrane-bound reactions without a matching increase in volume.
Carta 115
Domanda
A dye leaves heated cells faster than unheated cells. What conclusion is supported?
Risposta
Heating increased membrane permeability under the tested conditions; the data alone do not identify the exact molecular damage.
Carta 116
Domanda
What does an enzyme change in a reaction?
Risposta
It lowers activation energy, increasing reaction rate without changing the reaction's overall free-energy change.
Carta 117
Domanda
What makes a reaction exergonic?
Risposta
It releases free energy and has a negative change in free energy under the stated conditions.
Carta 118
Domanda
What are the overall inputs and outputs of photosynthesis?
Risposta
Carbon dioxide and water use light energy to produce carbohydrate and oxygen.
Carta 119
Domanda
What are the overall reactants and products of aerobic cellular respiration?
Risposta
Organic fuel and oxygen are converted mainly to carbon dioxide, water, and ATP, with heat released.
Carta 120
Domanda
How should reaction rate be calculated from product data?
Risposta
Divide the change in product amount by the elapsed time.
Carta 121
Domanda
What makes an enzyme substrate-specific?
Risposta
The active site's shape and chemical properties favor particular substrates.
Carta 122
Domanda
Where do the light reactions occur?
Risposta
In the thylakoid membranes of chloroplasts.
Carta 123
Domanda
Where does glycolysis occur?
Risposta
In the cytosol.
Carta 124
Domanda
What makes a reaction endergonic?
Risposta
It requires a net input of free energy and has a positive change in free energy.
Carta 125
Domanda
What is induced fit?
Risposta
Substrate binding shifts the enzyme's shape into a form that better supports catalysis.
Carta 126
Domanda
Where does the Calvin cycle occur?
Risposta
In the chloroplast stroma.
Carta 127
Domanda
What does glycolysis produce per glucose?
Risposta
Two pyruvate, a net two ATP, and two NADH.
Carta 128
Domanda
How can cells drive an endergonic reaction?
Risposta
They couple it to a sufficiently exergonic reaction so the combined free-energy change is negative.
Carta 129
Domanda
Why isn't an enzyme consumed by the reaction it catalyzes?
Risposta
It returns to a reusable form after products leave the active site.
Carta 130
Domanda
What do photosynthetic pigments do?
Risposta
They absorb particular wavelengths and transfer excitation energy into the light reactions.
Carta 131
Domanda
Does glycolysis require oxygen directly?
Risposta
No. It can run without oxygen if NAD⁺ is regenerated.
Carta 132
Domanda
What does ATP hydrolysis commonly provide?
Risposta
Usable free energy and a phosphate group that can change a molecule's reactivity or protein shape.
Carta 133
Domanda
How does substrate concentration affect rate at low concentrations?
Risposta
Rate usually rises because more substrate molecules collide with available active sites.
Carta 134
Domanda
Why do chlorophyll-containing leaves reflect green light?
Risposta
Chlorophyll absorbs green wavelengths less strongly than red and blue wavelengths.
Carta 135
Domanda
Where does pyruvate oxidation occur in a eukaryotic cell?
Risposta
In the mitochondrial matrix.
Carta 136
Domanda
Why is ATP called an energy-coupling molecule?
Risposta
Its hydrolysis links energy-releasing processes to cellular work.
Carta 137
Domanda
Why does enzyme rate plateau at high substrate concentration?
Risposta
Most active sites are occupied, so enzyme amount becomes limiting.
Carta 138
Domanda
What is photolysis of water?
Risposta
Light-driven splitting of water that supplies electrons and protons and releases oxygen.
Carta 139
Domanda
What happens during pyruvate oxidation?
Risposta
Each pyruvate becomes acetyl-CoA, releasing carbon dioxide and reducing NAD⁺ to NADH.
Carta 140
Domanda
Why measure an initial enzyme rate?
Risposta
Substrate depletion and product buildup have had less time to distort the rate.
Carta 141
Domanda
How can high temperature reduce enzyme activity?
Risposta
Heat can disrupt interactions that maintain the enzyme's functional shape.
Carta 142
Domanda
What is photosystem II's key contribution?
Risposta
It excites electrons and replaces them by oxidizing water.
Carta 143
Domanda
Where does the citric acid cycle occur in eukaryotes?
Risposta
In the mitochondrial matrix.
Carta 144
Domanda
What is oxidation?
Risposta
Loss of electrons, often accompanied by loss of hydrogen or gain of oxygen.
Carta 145
Domanda
Why does each enzyme have an optimal pH range?
Risposta
pH changes charges on amino-acid side chains and can alter binding or folding.
Carta 146
Domanda
What does the photosynthetic electron transport chain build?
Risposta
A proton gradient across the thylakoid membrane.
Carta 147
Domanda
What is the citric acid cycle's main energy role?
Risposta
It oxidizes acetyl groups and transfers electrons to NADH and FADH₂, making a small amount of ATP.
Carta 148
Domanda
In a photosynthesis experiment, why keep leaf area constant?
Risposta
Leaf area affects light capture and gas exchange, so changing it could confound the tested factor.
Carta 149
Domanda
How does a competitive inhibitor reduce enzyme activity?
Risposta
It competes with substrate for the active site.
Carta 150
Domanda
How does chloroplast ATP synthase make ATP?
Risposta
Protons flow from the thylakoid space to the stroma through ATP synthase, driving phosphorylation of ADP.
Carta 151
Domanda
Where is the respiratory electron transport chain located in eukaryotes?
Risposta
In the inner mitochondrial membrane.
Carta 152
Domanda
What is reduction?
Risposta
Gain of electrons, often accompanied by gain of hydrogen or loss of oxygen.
Carta 153
Domanda
How can extra substrate weaken competitive inhibition?
Risposta
More substrate increases the chance that substrate, rather than inhibitor, occupies the active site.
Carta 154
Domanda
What is photosystem I's key contribution?
Risposta
It re-energizes electrons used to reduce NADP⁺ to NADPH.
Carta 155
Domanda
What is oxygen's role in aerobic respiration?
Risposta
It is the final electron acceptor and combines with electrons and protons to form water.
Carta 156
Domanda
A respiration graph gets steeper after temperature rises. What does the slope show?
Risposta
A higher rate of the measured respiratory change, such as oxygen consumption per unit time.
Carta 157
Domanda
How does a noncompetitive inhibitor act?
Risposta
It binds away from the active site and changes enzyme activity, often by altering shape.
Carta 158
Domanda
What products of the light reactions feed the Calvin cycle?
Risposta
ATP and NADPH.
Carta 159
Domanda
How does electron transport create a proton gradient?
Risposta
Released electron energy pumps protons from the matrix to the intermembrane space.
Carta 160
Domanda
What do NADH and FADH₂ carry?
Risposta
High-energy electrons and associated hydrogen used in energy-transfer pathways.
Carta 161
Domanda
What is allosteric regulation?
Risposta
A regulator binds at one site and changes activity at another site on the protein.
Carta 162
Domanda
What does carbon fixation accomplish?
Risposta
It incorporates inorganic carbon dioxide into an organic molecule.
Carta 163
Domanda
What is oxidative phosphorylation?
Risposta
ATP production powered by electron transport and chemiosmosis.
Carta 164
Domanda
Why use multiple biological replicates in a rate experiment?
Risposta
They reveal natural variation and make the estimated treatment effect more reliable.
Carta 165
Domanda
What is fermentation's central purpose?
Risposta
It regenerates NAD⁺ so glycolysis can continue without an active electron transport chain.
Carta 166
Domanda
How does feedback inhibition control a pathway?
Risposta
A pathway's end product inhibits an earlier enzyme, reducing unnecessary production.
Carta 167
Domanda
What enzyme fixes carbon in the Calvin cycle?
Risposta
Rubisco.
Carta 168
Domanda
How does mitochondrial ATP synthase make ATP?
Risposta
Protons flow into the matrix through ATP synthase, driving ADP phosphorylation.
Carta 169
Domanda
Why do cells use stepwise electron transfers?
Risposta
They release energy in manageable increments that can be captured instead of lost mostly as heat.
Carta 170
Domanda
What is a cofactor?
Risposta
A nonprotein helper, often a metal ion or small organic coenzyme, required for some enzymes to function.
Carta 171
Domanda
What are the three broad phases of the Calvin cycle?
Risposta
Carbon fixation, reduction, and regeneration of the carbon-dioxide acceptor RuBP.
Carta 172
Domanda
How does lactic-acid fermentation regenerate NAD⁺?
Risposta
NADH reduces pyruvate to lactate, returning electrons to form NAD⁺.
Carta 173
Domanda
What is substrate-level phosphorylation?
Risposta
An enzyme transfers a phosphate directly from an intermediate to ADP.
Carta 174
Domanda
Error bars overlap broadly between two treatments. What is a careful conclusion?
Risposta
The graph alone does not show a clear difference; a suitable statistical analysis and design context are still needed.
Carta 175
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Why run an enzyme assay without enzyme?
Risposta
It measures the uncatalyzed background change and tests whether enzyme is required.
Carta 176
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How does alcoholic fermentation regenerate NAD⁺?
Risposta
Pyruvate loses carbon dioxide, and the remaining compound is reduced to ethanol as NADH becomes NAD⁺.
Carta 177
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What is G3P's role in photosynthesis?
Risposta
It is a three-carbon product that can leave the Calvin cycle and help build carbohydrates.
Carta 178
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Why are mitochondrial cristae useful?
Risposta
They increase inner-membrane area for electron transport chains and ATP synthase.
Carta 179
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What does phosphorylation often do to a molecule?
Risposta
It adds a phosphate group that can increase reactivity or alter a protein's shape and activity.
Carta 180
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A mutation lowers an enzyme's maximum rate but not substrate binding. What is a plausible effect?
Risposta
It may impair a catalytic step or reduce the number of functional enzyme molecules.
Carta 181
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Why must the Calvin cycle regenerate RuBP?
Risposta
RuBP is the carbon-dioxide acceptor needed for another turn of fixation.
Carta 182
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A chemical lowers oxygen use but not glycolysis. Which stage is most directly implicated?
Risposta
Aerobic electron transport or a process supplying it, because glycolysis itself does not consume oxygen.
Carta 183
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How would closed stomata affect photosynthesis?
Risposta
Carbon dioxide entry falls, which can limit carbon fixation even when light is available.
Carta 184
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A plant receives green light only. Predict its photosynthetic rate.
Risposta
It will usually be lower than under equally intense red or blue light because common chlorophylls absorb green poorly.
Carta 185
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Why does fermentation yield less ATP per glucose than aerobic respiration?
Risposta
It relies on glycolysis alone and leaves much of glucose's chemical energy in reduced end products.
Carta 186
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How does low ATP affect respiration pathway activity?
Risposta
It usually relieves inhibition of key enzymes, increasing fuel oxidation and ATP production.
Carta 187
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How can oxygen production estimate photosynthetic rate?
Risposta
Oxygen is a light-reaction product, so its production per unit time can serve as a rate proxy under controlled conditions.
Carta 188
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What happens to electron transport if oxygen is removed?
Risposta
The chain backs up because electrons lack a final acceptor; NADH accumulates and oxidative phosphorylation stops.
Carta 189
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Why does a light-response curve eventually level off?
Risposta
Another factor, such as carbon dioxide supply, temperature, or enzyme capacity, becomes limiting.
Carta 190
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An uncoupler lets protons cross the inner mitochondrial membrane. What happens?
Risposta
The gradient weakens, ATP production falls, and more energy is released as heat even if electron transport continues.
Carta 191
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What is direct-contact signaling?
Risposta
A membrane-bound molecule or cell junction communicates with an adjacent cell.
Carta 192
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What are the three broad stages of cell signaling?
Risposta
Reception, transduction, and response.
Carta 193
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How can a receptor mutation block a response even when ligand is present?
Risposta
The receptor may fail to bind ligand, change shape, or activate the first relay protein.
Carta 194
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What is negative feedback?
Risposta
A response reduces the original stimulus, helping stabilize a variable near a functional range.
Carta 195
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What happens during G1 phase?
Risposta
The cell grows, performs normal functions, and prepares for DNA replication.
Carta 196
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Cells show response values of 2, 7, and 18 after rising ligand doses. Describe the trend.
Risposta
The response increases with ligand dose across the tested range.
Carta 197
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What happens during reception?
Risposta
A ligand binds its receptor and changes the receptor's activity or shape.
Carta 198
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What is paracrine signaling?
Risposta
A cell releases a local regulator that acts on nearby target cells.
Carta 199
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What happens during S phase?
Risposta
DNA is replicated, producing sister chromatids for each chromosome.
Carta 200
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A response occurs without ligand. What pathway defect is plausible?
Risposta
A receptor or downstream relay protein may be constitutively active.
Carta 201
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What happens during signal transduction?
Risposta
Intracellular steps relay and often amplify information from the activated receptor.
Carta 202
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What is synaptic signaling?
Risposta
A neuron releases neurotransmitter across a short synaptic gap to a target cell.
Carta 203
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What happens during G2 phase?
Risposta
The cell grows, checks replicated DNA, and prepares the machinery for division.
Carta 204
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Why compare receptor-positive and receptor-negative cells?
Risposta
The comparison tests whether the receptor is necessary for the observed response.
Carta 205
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What counts as a cellular response?
Risposta
A change in gene expression, enzyme activity, ion flow, secretion, movement, division, or another cell behavior.
Carta 206
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How does insulin participate in negative feedback?
Risposta
High blood glucose promotes insulin release, which lowers blood glucose and reduces the original stimulus.
Carta 207
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What happens during mitosis?
Risposta
A eukaryotic nucleus separates duplicated chromosomes into two nuclei.
Carta 208
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What is endocrine signaling?
Risposta
Hormones travel through circulatory fluid to target cells that may be far away.
Carta 209
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What does a protein kinase do?
Risposta
It transfers a phosphate from ATP to a target protein.
Carta 210
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A drug blocks a kinase, and the final response disappears. What is supported?
Risposta
The kinase is required somewhere in that pathway under the tested conditions.
Carta 211
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What happens during cytokinesis?
Risposta
The cytoplasm divides to form separate daughter cells.
Carta 212
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How does glucagon participate in glucose homeostasis?
Risposta
Low blood glucose promotes glucagon release, which raises blood glucose toward the normal range.
Carta 213
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What does a protein phosphatase do?
Risposta
It removes a phosphate group from a target protein.
Carta 214
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What is a ligand?
Risposta
A signaling molecule that binds specifically to a receptor.
Carta 215
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What is the G1 checkpoint's broad role?
Risposta
It checks size, nutrients, growth signals, and DNA condition before replication.
Carta 216
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Why can't one inhibitor experiment prove a protein's exact pathway position?
Risposta
Off-target effects and indirect dependencies can produce the same outcome.
Carta 217
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Why are phosphorylation cascades reversible?
Risposta
Kinases add phosphates, while phosphatases remove them and reset pathway components.
Carta 218
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What is positive feedback?
Risposta
A response strengthens the initiating stimulus until a separate event stops the loop.
Carta 219
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What is the G2 checkpoint's broad role?
Risposta
It checks whether DNA replication is complete and damage is repaired before mitosis.
Carta 220
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Why don't all cells respond to the same hormone?
Risposta
Only cells with a compatible receptor and response machinery can respond.
Carta 221
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What is a second messenger?
Risposta
A small intracellular molecule or ion that relays a signal after receptor activation.
Carta 222
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How can rescue with an active downstream protein map a pathway?
Risposta
If the response returns despite an upstream block, the rescued protein likely acts downstream of that block.
Carta 223
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What does the spindle checkpoint verify?
Risposta
Every chromosome is correctly attached to spindle microtubules before sister chromatids separate.
Carta 224
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Why is blood clotting a positive-feedback process?
Risposta
Activated platelets recruit and activate more platelets until the break is sealed.
Carta 225
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Name two common second messengers.
Risposta
Cyclic AMP and calcium ions.
Carta 226
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A mutant receptor binds ligand but never becomes phosphorylated. Predict downstream signaling.
Risposta
It will likely fall or disappear if receptor phosphorylation is required to recruit relay proteins.
Carta 227
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How do cyclins regulate the cell cycle?
Risposta
Their concentrations rise and fall, activating cyclin-dependent kinases at specific stages.
Carta 228
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Why must DNA replicate before mitosis?
Risposta
Each daughter nucleus needs a complete copy of the genome.
Carta 229
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Where do receptors for many peptide hormones sit?
Risposta
In the plasma membrane, because these polar ligands do not readily cross the lipid bilayer.
Carta 230
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How can a signaling pathway amplify a weak signal?
Risposta
One activated component activates many downstream molecules at successive steps.
Carta 231
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What is the dependent variable in a ligand-dose experiment?
Risposta
The measured response, such as reporter activity, enzyme phosphorylation, or ion concentration.
Carta 232
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What do cyclin-dependent kinases do?
Risposta
When paired with cyclins, they phosphorylate targets that drive cell-cycle transitions.
Carta 233
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Why doesn't positive feedback usually maintain homeostasis by itself?
Risposta
It drives change away from the starting state and needs an external stop.
Carta 234
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What is a G protein's signaling role?
Risposta
It switches activity when bound to GTP and relays information from certain membrane receptors to effectors.
Carta 235
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How would you test whether calcium is required for a response?
Risposta
Block the calcium rise while keeping other conditions matched, then compare the response with a vehicle control.
Carta 236
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What is apoptosis?
Risposta
Programmed cell death that dismantles a cell in a controlled way.
Carta 237
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Where are receptors for many steroid hormones?
Risposta
Inside the cell, where lipid-soluble hormones can bind after crossing the membrane.
Carta 238
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How can an ion-channel receptor create a rapid response?
Risposta
Ligand binding opens or closes a pore, quickly changing ion movement and membrane conditions.
Carta 239
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Why test several ligand concentrations?
Risposta
A dose–response series can reveal sensitivity, saturation, and whether effects scale with ligand.
Carta 240
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Why is apoptosis useful in multicellular organisms?
Risposta
It removes damaged, infected, or unneeded cells with limited harm to neighbors.
Carta 241
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A thermostat-like pathway overshoots repeatedly. What defect is plausible?
Risposta
Delayed sensing or response can make negative feedback correct too late.
Carta 242
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How can an intracellular receptor affect gene expression?
Risposta
The ligand–receptor complex can act directly or indirectly as a transcription regulator.
Carta 243
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Cells lacking protein X divide despite DNA damage. Justify a checkpoint claim.
Risposta
Protein X likely supports a DNA-damage checkpoint because its absence links damage with continued division; rescue or pathway tests would strengthen the claim.
Carta 244
Domanda
What aligns at the metaphase plate?
Risposta
Duplicated chromosomes attached to spindle microtubules from opposite poles.
Carta 245
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How can failed checkpoints contribute to cancer?
Risposta
Cells with damage or abnormal signals can keep dividing instead of pausing or dying.
Carta 246
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How can gap junctions support communication?
Risposta
They connect neighboring animal-cell cytoplasms so small molecules and ions can pass directly.
Carta 247
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Why can the same ligand trigger different responses in two cell types?
Risposta
The cells can express different receptors, relay proteins, targets, or genes.
Carta 248
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Two pathways share one relay protein. What can happen if that protein is blocked?
Risposta
Both responses may weaken, showing pathway crosstalk or a shared component.
Carta 249
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During which mitotic stage do sister chromatids separate?
Risposta
Anaphase.
Carta 250
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What defines a malignant tumor?
Risposta
Its cells invade surrounding tissue and may spread to distant sites.
Carta 251
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How would loss of a feedback inhibitor affect a biosynthetic pathway?
Risposta
The pathway may stay active and overproduce its end product.
Carta 252
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What ends a signaling response?
Risposta
Ligand removal, receptor inactivation, GTP hydrolysis, messenger breakdown, or dephosphorylation can shut it down.
Carta 253
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A pathway diagram shows A activates B, and B inhibits C. Predict C after A activation.
Risposta
C activity should decrease, assuming the shown links are the relevant controlling interactions.
Carta 254
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A phosphatase that normally turns off an activated relay protein is inhibited. Predict the effect on that pathway.
Risposta
Phosphorylated targets may stay active longer, extending or strengthening the response.
Carta 255
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A drug prevents spindle formation. Where should the cycle stop?
Risposta
At the spindle checkpoint before anaphase, because chromosomes cannot attach correctly.
Carta 256
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What is the purpose of meiosis?
Risposta
It produces haploid cells and reshuffles inherited alleles for sexual reproduction.
Carta 257
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What is crossing over?
Risposta
Exchange of corresponding DNA segments between nonsister chromatids of homologous chromosomes.
Carta 258
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What does Mendel's law of segregation describe?
Risposta
An individual's two alleles for a gene separate into different gametes.
Carta 259
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Why do X-linked recessive traits often appear more frequently in XY individuals?
Risposta
They have only one X chromosome, so one recessive allele on it can determine the phenotype.
Carta 260
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What is incomplete dominance?
Risposta
The heterozygote has a phenotype intermediate between the two homozygotes.
Carta 261
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What does a chi-square goodness-of-fit test compare?
Risposta
Observed category counts with counts expected under a stated model.
Carta 262
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What is a homologous chromosome pair?
Risposta
Two chromosomes carrying the same gene locations, one inherited from each parent, possibly with different alleles.
Carta 263
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What does Mendel's law of independent assortment describe?
Risposta
Alleles of genes on different chromosomes, or far apart on one chromosome, assort independently during gamete formation.
Carta 264
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What is genetic linkage?
Risposta
Genes close together on the same chromosome tend to be inherited together.
Carta 265
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When does crossing over occur?
Risposta
During prophase I after homologs pair.
Carta 266
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How do sister chromatids differ from homologous chromosomes?
Risposta
Sister chromatids are replicated copies of one chromosome; homologs are the maternal and paternal versions of the same chromosome type.
Carta 267
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For Aa × Aa, what is the expected genotype ratio?
Risposta
1 AA : 2 Aa : 1 aa.
Carta 268
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How can linked genes produce recombinant offspring?
Risposta
Crossing over can exchange DNA between the gene locations.
Carta 269
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What is the usual null hypothesis for a Mendelian chi-square test?
Risposta
Any difference between observed and expected counts is due to chance sampling under the proposed inheritance model.
Carta 270
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What happens to homologous chromosomes in meiosis I?
Risposta
They pair and then separate into different cells.
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Carta 271
Domanda
For Aa × Aa with complete dominance, what is the expected phenotype ratio?
Risposta
3 dominant phenotype : 1 recessive phenotype.
Carta 272
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How does crossing over increase variation?
Risposta
It creates chromosomes with new combinations of parental alleles.
Carta 273
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What does recombination frequency estimate?
Risposta
Relative distance between linked genes; higher frequency generally means greater separation, up to the 50% limit.
Carta 274
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What happens to sister chromatids in meiosis II?
Risposta
Their centromeres separate, and the chromatids move into different cells.
Carta 275
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What rule finds the probability of either of two mutually exclusive outcomes?
Risposta
Add their individual probabilities.
Carta 276
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What is codominance?
Risposta
Both alleles contribute distinct, detectable products or traits in the heterozygote.
Carta 277
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How is a chi-square contribution calculated for one category?
Risposta
Subtract expected from observed, square the difference, and divide by expected.
Carta 278
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When do homologous chromosomes pair as tetrads?
Risposta
During prophase I.
Carta 279
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What rule finds the probability that independent events both occur?
Risposta
Multiply their individual probabilities.
Carta 280
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What is independent assortment?
Risposta
Each homologous pair orients independently at metaphase I, producing many maternal–paternal chromosome combinations.
Carta 281
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Why can't recombination frequency exceed 50%?
Risposta
At 50%, recombinant and parental combinations are equally common and the genes behave as if unlinked.
Carta 282
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What aligns at the metaphase I plate?
Risposta
Homologous pairs, with each homolog attached toward an opposite pole.
Carta 283
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What is a test cross?
Risposta
Crossing an individual with a dominant phenotype to a homozygous recessive individual to infer the unknown genotype.
Carta 284
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How can one gene have multiple alleles?
Risposta
More than two allele forms can exist in the population, although one diploid individual carries at most two.
Carta 285
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How are total chi-square and category contributions related?
Risposta
Total chi-square is the sum of all category contributions.
Carta 286
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What separates during anaphase I?
Risposta
Homologous chromosomes; sister chromatids remain joined.
Carta 287
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How does random fertilization increase variation?
Risposta
Any one genetically varied gamete from one parent can fuse with any compatible gamete from the other.
Carta 288
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A test cross yields about half recessive offspring. What genotype is supported for the unknown parent?
Risposta
Heterozygous.
Carta 289
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What is nondisjunction?
Risposta
Failure of homologous chromosomes or sister chromatids to separate normally.
Carta 290
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What aligns during metaphase II?
Risposta
Individual duplicated chromosomes in each haploid cell.
Carta 291
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What is polygenic inheritance?
Risposta
Multiple genes contribute to one trait, often producing continuous phenotypic variation.
Carta 292
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For a simple goodness-of-fit test, how are degrees of freedom found?
Risposta
Number of categories minus one.
Carta 293
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Which meiotic events create variation before fertilization?
Risposta
Crossing over and independent assortment.
Carta 294
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How does ploidy change during meiosis?
Risposta
Homolog separation reduces diploid cells to haploid cells; meiosis II separates chromatids without another ploidy reduction.
Carta 295
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What pedigree pattern often suggests a recessive trait?
Risposta
Unaffected parents can have an affected child, if both parents carry the allele.
Carta 296
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How can meiotic nondisjunction affect gametes?
Risposta
It can produce gametes with an extra or missing chromosome.
Carta 297
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What is pleiotropy?
Risposta
One gene influences multiple phenotypic traits.
Carta 298
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Why is there no second DNA replication before meiosis II?
Risposta
The goal is to separate existing sister chromatids, not duplicate the genome again.
Carta 299
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What does a p-value below the chosen threshold support?
Risposta
Rejecting the null model because the observed deviation would be unlikely if that model were correct.
Carta 300
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Why are siblings genetically different even with the same parents?
Risposta
They inherit different allele combinations through crossing over, independent assortment, and random fertilization.
Carta 301
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Why do small families often deviate from expected Mendelian ratios?
Risposta
Probability ratios describe long-run expectations; random sampling variation is large with few offspring.
Carta 302
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A diploid cell has six chromosomes. How many chromosomes should each normal meiotic product have?
Risposta
Three.
Carta 303
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A trisomic zygote forms after fertilization. What meiotic error is a likely cause?
Risposta
Nondisjunction produced a gamete carrying an extra copy of that chromosome.
Carta 304
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Why can identical genotypes show different phenotypes?
Risposta
Environmental conditions and developmental variation can alter gene expression or trait development.
Carta 305
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What does failing to reject a genetic null hypothesis mean?
Risposta
The data do not show a significant departure from the model; they do not prove the model true.
Carta 306
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How do DNA and RNA sugars differ?
Risposta
DNA contains deoxyribose; RNA contains ribose.
Carta 307
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What does semiconservative DNA replication produce?
Risposta
Each daughter DNA molecule contains one original strand and one newly synthesized strand.
Carta 308
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What is transcription?
Risposta
Synthesis of RNA using DNA as a template.
Carta 309
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What is a point mutation?
Risposta
A change affecting one nucleotide pair.
Carta 310
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What is an operon?
Risposta
A group of prokaryotic genes controlled together and transcribed from one promoter.
Carta 311
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Why can muscle and nerve cells differ despite having the same genome?
Risposta
They express different sets and amounts of genes.
Carta 312
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What must a virus use from its host?
Risposta
Host resources and at least some host-cell machinery to copy or express its genome and produce new particles.
Carta 313
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What does PCR do?
Risposta
It amplifies a chosen DNA region through repeated cycles of strand separation, primer binding, and extension.
Carta 314
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What enzyme performs transcription?
Risposta
RNA polymerase.
Carta 315
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What does helicase do during replication?
Risposta
It unwinds the double helix and separates the template strands.
Carta 316
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How does a repressor reduce transcription?
Risposta
It binds regulatory DNA and blocks or hinders transcription machinery.
Carta 317
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What is a silent mutation?
Risposta
A nucleotide change that does not change the encoded amino acid.
Carta 318
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What does a promoter do?
Risposta
It marks where transcription machinery assembles and helps set the transcription start and direction.
Carta 319
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What does topoisomerase do ahead of a replication fork?
Risposta
It relieves twisting strain caused by DNA unwinding.
Carta 320
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How does an inducer affect an inducible operon?
Risposta
It disables the repressor or otherwise turns transcription on when the pathway's substrate is present.
Carta 321
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How do DNA and RNA bases differ?
Risposta
DNA uses thymine, while RNA uses uracil; both also use adenine, cytosine, and guanine.
Carta 322
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Which DNA strand does RNA polymerase read?
Risposta
The template strand, read 3′→5′ while RNA is built 5′→3′.
Carta 323
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Why is an RNA primer needed for DNA replication?
Risposta
DNA polymerase can extend an existing 3′ end but cannot start a strand from nothing.
Carta 324
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How does a corepressor affect a repressible operon?
Risposta
It activates a repressor, turning off genes when the pathway's end product is abundant.
Carta 325
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What is a missense mutation?
Risposta
A nucleotide change that substitutes one amino acid for another.
Carta 326
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How does an mRNA sequence relate to the coding DNA strand?
Risposta
It matches the coding strand except RNA has uracil in place of thymine.
Carta 327
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What does primase do?
Risposta
It builds short RNA primers.
Carta 328
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Why is the lac operon strongly expressed when lactose is present and glucose is scarce?
Risposta
Lactose relieves repression, while low glucose supports positive activation of transcription.
Carta 329
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Why are primers essential in PCR?
Risposta
They define the target boundaries and provide 3′ ends for DNA polymerase.
Carta 330
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What is the primary RNA transcript in a eukaryote?
Risposta
The initial RNA copy before processing.
Carta 331
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In which direction does DNA polymerase synthesize DNA?
Risposta
5′→3′ by adding nucleotides to a 3′ end.
Carta 332
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Why is the trp operon usually off when tryptophan is abundant?
Risposta
Tryptophan acts as a corepressor, enabling repression of biosynthetic genes.
Carta 333
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What holds complementary DNA bases together?
Risposta
Hydrogen bonds: adenine pairs with thymine, and cytosine pairs with guanine.
Carta 334
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What happens during RNA splicing?
Risposta
Introns are removed and exons are joined.
Carta 335
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Why is the leading strand synthesized continuously?
Risposta
Its template orientation lets polymerase follow the replication fork while synthesizing 5′→3′.
Carta 336
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How can histone acetylation affect transcription?
Risposta
It often loosens chromatin and makes DNA more accessible to transcription machinery.
Carta 337
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What is a nonsense mutation?
Risposta
A nucleotide change that creates a premature stop codon.
Carta 338
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What do the 5′ cap and poly-A tail help do?
Risposta
They protect eukaryotic mRNA and support export and translation.
Carta 339
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Why is the lagging strand synthesized in fragments?
Risposta
Its template orientation forces repeated 5′→3′ synthesis away from the moving fork.
Carta 340
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How can DNA methylation near a promoter affect transcription?
Risposta
It often reduces transcription by limiting access or recruiting repressive proteins.
Carta 341
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How does gel electrophoresis separate DNA fragments?
Risposta
An electric field pulls negatively charged DNA through a matrix; smaller fragments usually travel farther.
Carta 342
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How can alternative splicing increase protein diversity?
Risposta
Different exon combinations from one transcript can produce different mRNAs and polypeptides.
Carta 343
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What are Okazaki fragments?
Risposta
Short DNA segments made on the lagging strand.
Carta 344
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What does a transcription factor do?
Risposta
It binds regulatory DNA and helps increase or decrease transcription of specific genes.
Carta 345
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Why are DNA strands antiparallel?
Risposta
Their sugar–phosphate backbones run in opposite 5′→3′ directions.
Carta 346
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What is translation?
Risposta
Ribosomes use an mRNA codon sequence to build a polypeptide.
Carta 347
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What does DNA ligase do?
Risposta
It seals breaks in the sugar–phosphate backbone, joining DNA fragments.
Carta 348
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What is a frameshift mutation?
Risposta
An insertion or deletion not in multiples of three that shifts downstream codon grouping.
Carta 349
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How can an enhancer influence a distant promoter?
Risposta
DNA looping brings enhancer-bound activators near the transcription machinery.
Carta 350
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What does a codon specify?
Risposta
An amino acid or a translation stop signal.
Carta 351
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What do restriction enzymes do?
Risposta
They cut DNA at particular recognition sequences.
Carta 352
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What gives a nucleic-acid strand its 5′ and 3′ ends?
Risposta
The chemical groups on the sugar: a 5′ phosphate end and a 3′ hydroxyl end.
Carta 353
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How does proofreading improve replication accuracy?
Risposta
DNA polymerases detect and replace many incorrectly paired nucleotides.
Carta 354
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What does a tRNA anticodon do?
Risposta
It base-pairs with an mRNA codon so the attached amino acid is placed correctly.
Carta 355
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Why can a promoter mutation affect protein amount?
Risposta
It can change transcription-factor or RNA-polymerase binding and alter transcription rate.
Carta 356
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How can microRNA reduce gene expression?
Risposta
It base-pairs with target mRNA and promotes degradation or blocks translation.
Carta 357
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What maintains a differentiated cell's identity?
Risposta
Stable regulatory networks and chromatin states keep characteristic genes active or silent.
Carta 358
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What are the ribosome's broad roles?
Risposta
It positions mRNA and tRNAs and catalyzes peptide-bond formation.
Carta 359
Domanda
How can an RNA virus generate genetic variation quickly?
Risposta
Many viral RNA polymerases lack strong proofreading, so replication introduces mutations frequently.
Carta 360
Domanda
What can bacterial transformation demonstrate?
Risposta
Cells can take up external DNA and express a selectable or observable trait.
Carta 361
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Why is RNA usually more structurally varied than double-stranded DNA?
Risposta
A single RNA strand can fold back on itself through internal base pairing.
Carta 362
Domanda
What usually marks translation initiation?
Risposta
A start codon positioned with an initiator tRNA and ribosomal subunits.
Carta 363
Domanda
What problem do telomeres help solve?
Risposta
They protect chromosome ends from losing essential genes during repeated linear-DNA replication.
Carta 364
Domanda
Why can an intron splice-site mutation affect protein sequence?
Risposta
Incorrect splicing can remove exon sequence or retain intron sequence in the mature mRNA.
Carta 365
Domanda
How can protein degradation regulate a pathway quickly?
Risposta
Destroying a key protein lowers its activity without waiting for transcription to change.
Carta 366
Domanda
What happens at a stop codon?
Risposta
A release factor ends translation and frees the polypeptide.
Carta 367
Domanda
How can a signal change cell specialization?
Risposta
It can activate transcription factors that launch a new gene-expression program.
Carta 368
Domanda
What is a retrovirus's information flow?
Risposta
Viral RNA is reverse-transcribed into DNA, which can integrate into the host genome.
Carta 369
Domanda
What does DNA sequencing reveal directly?
Risposta
The order of nucleotides in the analyzed DNA; biological effects require further interpretation.
Carta 370
Domanda
Why is the genetic code called redundant?
Risposta
More than one codon can specify the same amino acid.
Carta 371
Domanda
Where does nucleotide sequence store information?
Risposta
The order of bases encodes information that can be copied, transcribed, or translated.
Carta 372
Domanda
Why is replication called bidirectional?
Risposta
Two forks usually move away from each origin in opposite directions.
Carta 373
Domanda
Why doesn't every DNA mutation change phenotype?
Risposta
It may occur outside a functional sequence, be silent, have a mild effect, or be masked by another allele or environment.
Carta 374
Domanda
How does a free ribosome's product usually differ from a rough-ER ribosome's product?
Risposta
Free ribosomes often make cytosolic proteins; ER-bound ribosomes make many secreted, membrane, and endomembrane proteins.
Carta 375
Domanda
Why can one signal coordinate many genes?
Risposta
A shared transcription regulator or signaling pathway can control multiple target promoters.
Carta 376
Domanda
Why does cell specialization depend on selective gene expression rather than gene loss?
Risposta
Most specialized cells retain the genome but use only the genes needed for their role.
Carta 377
Domanda
Why are viruses not described as independently living cells?
Risposta
They lack cellular metabolism and cannot reproduce without a host cell.
Carta 378
Domanda
A coding DNA triplet is 5′-ATG-3′. What is the matching mRNA codon?
Risposta
5′-AUG-3′.
Carta 379
Domanda
A PCR band is absent. Why isn't gene absence the only explanation?
Risposta
Poor DNA quality, wrong primers, inhibitors, or failed reaction conditions can also prevent amplification.
Carta 380
Domanda
Why can protein function require steps after translation?
Risposta
The polypeptide may need folding, cleavage, chemical modification, or assembly with other subunits.
Carta 381
Domanda
How do fossils support evolution?
Risposta
They document organisms and transitions through time, including appearance, change, and extinction.
Carta 382
Domanda
What conditions are required for natural selection?
Risposta
Individuals vary, some variation is heritable, and variants differ in survival or reproductive success in that environment.
Carta 383
Domanda
What is artificial selection?
Risposta
Humans choose which organisms reproduce based on desired heritable traits.
Carta 384
Domanda
What does an allele frequency measure?
Risposta
The fraction of all copies of a gene in a population represented by one allele.
Carta 385
Domanda
What does a node on a phylogenetic tree represent?
Risposta
A common ancestor where descendant lineages diverge.
Carta 386
Domanda
What is biological speciation?
Risposta
Evolution of reproductive isolation between populations, producing independently evolving lineages.
Carta 387
Domanda
What is extinction?
Risposta
Permanent loss of a species when no living members remain.
Carta 388
Domanda
A pesticide-treated population becomes mostly resistant. What evidence distinguishes selection from acclimation?
Risposta
Resistance should be heritable and increase across generations through differential reproduction, not just appear temporarily in exposed individuals.
Carta 389
Domanda
What changes during evolution by natural selection?
Risposta
Allele frequencies in a population across generations.
Carta 390
Domanda
For two alleles under Hardy–Weinberg notation, what does p + q equal?
Risposta
1.
Carta 391
Domanda
What is a clade?
Risposta
An ancestor and all of its descendants.
Carta 392
Domanda
What does homologous anatomy suggest?
Risposta
Similar underlying structures with different functions can indicate inheritance from a common ancestor.
Carta 393
Domanda
Do individual organisms evolve by natural selection?
Risposta
No. Individuals are selected; populations evolve as inherited variants change in frequency.
Carta 394
Domanda
Under Hardy–Weinberg equilibrium, what does p² represent?
Risposta
Expected frequency of one homozygous genotype.
Carta 395
Domanda
What is a shared derived character?
Risposta
A trait that evolved in a common ancestor and helps identify one of its descendant clades.
Carta 396
Domanda
What is mutation's evolutionary role?
Risposta
It creates new alleles, the ultimate source of new genetic variation.
Carta 397
Domanda
What is biological fitness?
Risposta
Relative contribution of viable, reproducing offspring to the next generation in a particular environment.
Carta 398
Domanda
Under Hardy–Weinberg equilibrium, what does 2pq represent?
Risposta
Expected frequency of heterozygotes.
Carta 399
Domanda
Which two tips on a tree are most closely related?
Risposta
Those sharing the most recent common ancestor, regardless of how close their names appear on the page.
Carta 400
Domanda
What is a vestigial structure?
Risposta
A reduced feature inherited from ancestors that has lost much or all of its earlier function.
Carta 401
Domanda
What is an adaptation?
Risposta
A heritable trait that became common because it improved fitness in past environments.
Carta 402
Domanda
Under Hardy–Weinberg equilibrium, what does q² represent?
Risposta
Expected frequency of the other homozygous genotype.
Carta 403
Domanda
How does recombination affect evolution?
Risposta
It reshuffles existing alleles into new combinations but does not itself create new alleles.
Carta 404
Domanda
Does rotating branches around a node change relationships?
Risposta
No. The branching pattern stays the same.
Carta 405
Domanda
Why isn't an adaptation always beneficial in every setting?
Risposta
Fitness effects depend on the environment and can involve tradeoffs.
Carta 406
Domanda
What are the Hardy–Weinberg assumptions?
Risposta
A very large population, random mating, no mutation, no migration, and no natural selection at the locus.
Carta 407
Domanda
How can embryological similarities support common ancestry?
Risposta
Shared developmental patterns can reflect inherited developmental genes and pathways.
Carta 408
Domanda
What is gene flow?
Risposta
Movement of alleles between populations through migration and reproduction.
Carta 409
Domanda
Does natural selection create needed mutations?
Risposta
No. Mutations arise without regard to need; selection changes the frequencies of their inherited effects.
Carta 410
Domanda
Why is Hardy–Weinberg equilibrium useful?
Risposta
It provides a null model for detecting or reasoning about evolutionary change.
Carta 411
Domanda
Does left-to-right tip order show evolutionary progress?
Risposta
No. Tip order is a drawing choice, not a ranking from primitive to advanced.
Carta 412
Domanda
What is allopatric speciation?
Risposta
Geographic separation reduces gene flow, allowing populations to diverge.
Carta 413
Domanda
What is directional selection?
Risposta
Selection favors one end of a phenotypic range, shifting the population mean.
Carta 414
Domanda
If q² = 0.09, what is q?
Risposta
0.30.
Carta 415
Domanda
Why is DNA sequence similarity evidence for relatedness?
Risposta
Related lineages inherit sequences from common ancestors, with differences accumulating over time.
Carta 416
Domanda
How does gene flow often affect differences between populations?
Risposta
It tends to make allele frequencies more similar.
Carta 417
Domanda
What is stabilizing selection?
Risposta
Selection favors intermediate phenotypes and removes extremes.
Carta 418
Domanda
If q = 0.30, what is p?
Risposta
0.70.
Carta 419
Domanda
What can branch length mean?
Risposta
Only what the figure defines—sometimes time or amount of change, and sometimes nothing quantitative.
Carta 420
Domanda
What is sympatric speciation?
Risposta
Reproductive isolation evolves without geographic separation, for example through polyploidy or strong niche and mating differences.
Carta 421
Domanda
What is disruptive selection?
Risposta
Selection favors both extremes over intermediate phenotypes.
Carta 422
Domanda
If p = 0.70 and q = 0.30, what is 2pq?
Risposta
0.42.
Carta 423
Domanda
Why include an untreated population in a selection experiment?
Risposta
It shows how allele or trait frequencies change without the selective treatment.
Carta 424
Domanda
Why is the nearly universal genetic code evidence of common ancestry?
Risposta
A deeply conserved information system is most simply explained by inheritance from early shared ancestors.
Carta 425
Domanda
What is balancing selection?
Risposta
Natural selection that maintains two or more alleles in a population, such as through heterozygote advantage or selection that varies across environments.
Carta 426
Domanda
What is genetic drift?
Risposta
Random change in allele frequencies caused by chance sampling across generations.
Carta 427
Domanda
If 16% of a Hardy–Weinberg population shows a recessive phenotype, what is q?
Risposta
0.40, because q is the square root of 0.16.
Carta 428
Domanda
Why use an outgroup in tree analysis?
Risposta
It helps infer which character states are ancestral versus derived in the focal group.
Carta 429
Domanda
What is a prezygotic barrier?
Risposta
A barrier that prevents mating or fertilization.
Carta 430
Domanda
Allele A rises from 0.20 to 0.45. Describe the evolutionary result.
Risposta
The population evolved at that locus because allele frequency changed.
Carta 431
Domanda
How does biogeography support evolution?
Risposta
Species distributions often match isolation history, dispersal, and descent from nearby ancestors.
Carta 432
Domanda
What is sexual selection?
Risposta
Differences in mating success drive changes in traits that affect mate attraction or competition.
Carta 433
Domanda
When is genetic drift strongest?
Risposta
In small populations.
Carta 434
Domanda
Why can a rare recessive allele persist?
Risposta
Selection cannot remove copies hidden in heterozygotes as efficiently as copies expressed in homozygotes.
Carta 435
Domanda
How can molecular data revise a phylogenetic tree?
Risposta
Sequence comparisons can reveal relationships not obvious from morphology or distinguish convergence from homology.
Carta 436
Domanda
What is a postzygotic barrier?
Risposta
A barrier that reduces hybrid survival, fertility, or later-generation success after fertilization.
Carta 437
Domanda
How can rapid environmental change increase extinction risk?
Risposta
Populations may lack enough suitable variation or time to adapt or move.
Carta 438
Domanda
A small island population loses alleles after a storm. Which mechanism is most direct?
Risposta
Genetic drift through a bottleneck.
Carta 439
Domanda
What is convergent evolution?
Risposta
Unrelated lineages independently evolve similar traits under similar selective pressures.
Carta 440
Domanda
Why can antibiotic resistance spread rapidly?
Risposta
Treatment strongly favors resistant variants already present or newly introduced, which leave more descendants.
Carta 441
Domanda
What is a bottleneck effect?
Risposta
A sharp population reduction leaves a random, often less diverse sample of the original gene pool.
Carta 442
Domanda
How do genotype counts yield allele frequency?
Risposta
Count two copies from each homozygote and one from each heterozygote, then divide by twice the number of diploid individuals.
Carta 443
Domanda
What is maximum parsimony in tree building?
Risposta
Preferring the tree that requires the fewest evolutionary changes under the model.
Carta 444
Domanda
How can different breeding times isolate populations?
Risposta
Temporal isolation prevents individuals from mating even when they share a location.
Carta 445
Domanda
Why can mass extinctions reshape evolution?
Risposta
They remove many lineages and open ecological opportunities for survivors.
Carta 446
Domanda
Two similar traits evolved on distant tree branches. What explanation should be evaluated?
Risposta
Convergent evolution under similar selection, alongside the possibility of an incorrect tree or unrecognized homology.
Carta 447
Domanda
Why are analogous structures weak evidence of close ancestry?
Risposta
Their similar function may have evolved independently rather than from the same ancestral structure.
Carta 448
Domanda
Why doesn't natural selection produce perfection?
Risposta
It works with existing variation under tradeoffs, historical constraints, chance, and changing environments.
Carta 449
Domanda
What is a founder effect?
Risposta
A new population starts from a small, nonrepresentative sample of a source population.
Carta 450
Domanda
Observed genotypes differ from Hardy–Weinberg expectations. What is supported?
Risposta
At least one model assumption may not hold, or sampling error may matter; the deviation alone does not identify the cause.
Carta 451
Domanda
Why is a phylogenetic tree a hypothesis?
Risposta
It is an evidence-based reconstruction that can change when new data or methods appear.
Carta 452
Domanda
How can behavioral differences cause isolation?
Risposta
Different courtship signals reduce mating between populations.
Carta 453
Domanda
What evidence can test origin-of-life hypotheses?
Risposta
Chemistry experiments, geological records, molecular comparisons, and plausible self-replicating or membrane-forming systems.
Carta 454
Domanda
How should fitness be compared in an experiment?
Risposta
Measure relative reproductive contribution, such as viable offspring, under the same environmental conditions.
Carta 455
Domanda
What does the fossil record not provide?
Risposta
A complete sample of every organism or every transitional population.
Carta 456
Domanda
How can a neutral trait change in frequency?
Risposta
Genetic drift can shift it by chance, especially in small populations.
Carta 457
Domanda
How can drift reduce adaptive potential?
Risposta
It can remove alleles and lower genetic diversity needed under future environmental change.
Carta 458
Domanda
Why does a large population support Hardy–Weinberg stability?
Risposta
Chance sampling has less effect on allele frequencies, reducing drift.
Carta 459
Domanda
If A and B share a more recent node with each other than either shares with C, what does that mean?
Risposta
A and B are sister taxa and share a more recent common ancestor with each other than with C.
Carta 460
Domanda
What is adaptive radiation?
Risposta
Rapid diversification of one ancestral lineage into species using different ecological roles.
Carta 461
Domanda
What can experiments producing organic molecules from simple chemicals show?
Risposta
That some building blocks can form under modeled conditions; they do not recreate or prove the exact origin of life.
Carta 462
Domanda
A correlation links beak size with survival. Why isn't causation settled?
Risposta
Other traits or habitats may covary with beak size; controlled or multivariable evidence is needed.
Carta 463
Domanda
Why does agreement among fossils, anatomy, and molecules strengthen an evolutionary claim?
Risposta
Independent evidence types pointing to the same history make alternative explanations less plausible.
Carta 464
Domanda
A drought favors deeper beaks. What must be measured to show selection?
Risposta
Heritable beak variation and differences in survival or reproduction linked to beak depth.
Carta 465
Domanda
Why can artificial selection produce unintended traits?
Risposta
Selected genes may be linked to other alleles, and inbreeding can expose harmful recessive alleles.
Carta 466
Domanda
What data are needed to test Hardy–Weinberg genotype expectations?
Risposta
Population genotype counts or reliable genotype frequencies for the locus.
Carta 467
Domanda
Why doesn't one living species count as the ancestor of another on a typical tree?
Risposta
Living tips represent lineages that have both evolved since their shared ancestral lineage.
Carta 468
Domanda
Why can reduced gene flow accelerate divergence?
Risposta
Populations retain separate mutations, drift independently, and respond to different selective pressures.
Carta 469
Domanda
Why are ribozymes relevant to early-life hypotheses?
Risposta
RNA can both store information and catalyze reactions, offering a possible bridge before modern DNA–protein systems.
Carta 470
Domanda
What makes an evolutionary argument strong?
Risposta
A clear claim, relevant population-level evidence, and reasoning that connects inheritance and differential reproduction to the observed change.
Carta 471
Domanda
How can a directional response help an organism?
Risposta
Moving toward resources or away from hazards can improve survival and reproduction.
Carta 472
Domanda
What is a trophic level?
Risposta
A feeding position in the flow of energy through an ecosystem.
Carta 473
Domanda
What processes move carbon into and out of biological molecules?
Risposta
Photosynthesis fixes carbon; respiration, decomposition, and combustion release carbon dioxide.
Carta 474
Domanda
What does exponential population growth assume?
Risposta
Resources are effectively unlimited and the per-capita growth rate stays constant.
Carta 475
Domanda
What is a density-dependent limiting factor?
Risposta
Its effect strengthens as population density rises, such as competition, disease, or predation.
Carta 476
Domanda
What is a keystone species?
Risposta
A species whose ecological effect is disproportionately large relative to its abundance.
Carta 477
Domanda
What are three levels of biodiversity?
Risposta
Genetic diversity, species diversity, and ecosystem diversity.
Carta 478
Domanda
What is the independent variable in a fertilizer–algae experiment?
Risposta
The fertilizer amount or nutrient concentration deliberately changed.
Carta 479
Domanda
What shape represents exponential growth over time?
Risposta
A J-shaped curve.
Carta 480
Domanda
What do primary producers do?
Risposta
They capture external energy and build organic molecules from inorganic carbon.
Carta 481
Domanda
What is a density-independent limiting factor?
Risposta
Its effect is not primarily set by population density, such as a severe freeze or wildfire.
Carta 482
Domanda
Why is nitrogen fixation necessary?
Risposta
Most organisms cannot use atmospheric nitrogen gas directly, so it must be converted to biologically available compounds.
Carta 483
Domanda
What does logistic growth add to the exponential model?
Risposta
Growth slows as population size approaches carrying capacity.
Carta 484
Domanda
What is gross primary productivity?
Risposta
The total rate at which producers capture energy in organic matter.
Carta 485
Domanda
What is competition?
Risposta
An interaction in which organisms using the same limited resource reduce one another's access or fitness.
Carta 486
Domanda
What is ecological succession?
Risposta
Change in community composition after new habitat forms or a disturbance alters an existing community.
Carta 487
Domanda
What shape represents ideal logistic growth?
Risposta
An S-shaped curve.
Carta 488
Domanda
What is net primary productivity?
Risposta
Gross primary productivity minus producers' respiratory energy use.
Carta 489
Domanda
Why does genetic diversity matter for conservation?
Risposta
It increases the range of inherited responses available under disease or environmental change.
Carta 490
Domanda
What organisms perform much biological nitrogen fixation?
Risposta
Certain prokaryotes, including free-living and symbiotic bacteria.
Carta 491
Domanda
What is carrying capacity?
Risposta
The population size an environment can sustain over time under current conditions.
Carta 492
Domanda
Why is net primary productivity important to consumers?
Risposta
It is the producer biomass and energy available for growth and the next trophic levels.
Carta 493
Domanda
What is competitive exclusion?
Risposta
Species with identical limiting-resource niches cannot coexist indefinitely under stable conditions.
Carta 494
Domanda
How do primary and secondary succession differ?
Risposta
Primary succession begins without developed soil; secondary succession begins where soil remains.
Carta 495
Domanda
Why can carrying capacity change?
Risposta
Resources, habitat, climate, competitors, disease, and disturbance can change.
Carta 496
Domanda
Why does available energy decline up a food chain?
Risposta
Organisms use much energy for metabolism and lose it as heat and waste rather than storing it as biomass.
Carta 497
Domanda
What is an ecosystem service?
Risposta
A benefit people receive from ecosystems, such as pollination, water purification, soil formation, or climate regulation.
Carta 498
Domanda
What does nitrification do?
Risposta
Microbes oxidize ammonium to nitrite and then nitrate.
Carta 499
Domanda
What does per-capita growth rate measure?
Risposta
Population change per individual per unit time.
Carta 500
Domanda
What is ecological efficiency?
Risposta
The percentage of energy or production transferred from one trophic level to the next.
Carta 501
Domanda
What is resource partitioning?
Risposta
Competing species use different resources, places, or times, reducing direct overlap.
Carta 502
Domanda
What is resilience in an ecosystem?
Risposta
The ability to recover structure or function after disturbance.
Carta 503
Domanda
How is population growth estimated from births, deaths, immigration, and emigration?
Risposta
Births + immigration − deaths − emigration.
Carta 504
Domanda
If producers store 10,000 kJ and primary consumers receive 10%, how much do they receive?
Risposta
1,000 kJ.
Carta 505
Domanda
How does habitat fragmentation affect populations?
Risposta
It shrinks and isolates habitat, reducing movement and gene flow while increasing edge effects.
Carta 506
Domanda
Why sample several sites within each habitat?
Risposta
Replication captures spatial variation and reduces the chance that one unusual site drives the result.
Carta 507
Domanda
A population grows from 200 to 230 in one year. What is its percent growth?
Risposta
15%, because the increase of 30 divided by 200 is 0.15.
Carta 508
Domanda
What is a circadian rhythm?
Risposta
An internal roughly 24-hour cycle that environmental cues can reset.
Carta 509
Domanda
Why are food webs more realistic than simple food chains?
Risposta
Most species eat or are eaten by multiple species, creating connected pathways.
Carta 510
Domanda
What does denitrification do?
Risposta
Microbes convert nitrate to nitrogen gases, returning nitrogen to the atmosphere.
Carta 511
Domanda
What characterizes an r-selected life-history strategy?
Risposta
Many offspring, early reproduction, and relatively low investment per offspring in variable environments.
Carta 512
Domanda
What is mutualism?
Risposta
An interaction that benefits both species.
Carta 513
Domanda
What is resistance in an ecosystem?
Risposta
The ability to remain relatively unchanged during disturbance.
Carta 514
Domanda
How can climate change shift species ranges?
Risposta
Organisms track suitable temperature, moisture, seasons, or interacting species when movement is possible.
Carta 515
Domanda
What characterizes a K-selected life-history strategy?
Risposta
Fewer offspring, later reproduction, and higher investment per offspring near carrying capacity.
Carta 516
Domanda
A population curve levels near 800. What does the model suggest?
Risposta
About 800 is the carrying capacity under those measured conditions, not a permanent universal value.
Carta 517
Domanda
How can seasonal cues affect reproduction?
Risposta
Changes such as day length can trigger hormonal and behavioral shifts timed to favorable conditions.
Carta 518
Domanda
What role do decomposers play?
Risposta
They break down dead material and waste, returning nutrients to forms other organisms can use.
Carta 519
Domanda
Why can phosphorus limit ecosystems?
Risposta
It is essential but often released slowly from rocks and lacks a large atmospheric gas phase.
Carta 520
Domanda
What does a Type I survivorship curve show?
Risposta
High survival through early and middle life, followed by a steep decline at older ages.
Carta 521
Domanda
What is commensalism?
Risposta
One species benefits while the other has no clear benefit or harm.
Carta 522
Domanda
Why can diversity improve ecosystem stability?
Risposta
Multiple species or response types can keep functions going when one component declines.
Carta 523
Domanda
Why can overharvesting destabilize a population?
Risposta
Removal faster than replacement lowers abundance and can alter age structure or genetic diversity.
Carta 524
Domanda
Predator and prey peaks alternate over time. What can the graph establish?
Risposta
Their abundances covary with a lag; the graph alone cannot prove the predator caused every prey change.
Carta 525
Domanda
What is acclimation?
Risposta
A reversible phenotypic adjustment by an individual to an environmental change.
Carta 526
Domanda
Does energy cycle through an ecosystem?
Risposta
No. Energy flows through and is ultimately dissipated as heat; matter cycles.
Carta 527
Domanda
How does the water cycle connect ecosystems?
Risposta
Evaporation, transpiration, condensation, precipitation, runoff, and infiltration move water and dissolved materials.
Carta 528
Domanda
What does a Type II survivorship curve show?
Risposta
A roughly constant mortality risk across ages.
Carta 529
Domanda
What is parasitism?
Risposta
A parasite benefits while reducing its host's fitness.
Carta 530
Domanda
What is an invasive species?
Risposta
A nonnative species that spreads and causes ecological, economic, or human-health harm.
Carta 531
Domanda
How can a wildlife corridor help fragmented populations?
Risposta
It supports movement, recolonization, and gene flow between habitat patches.
Carta 532
Domanda
How should biodiversity be compared when sample effort differs?
Risposta
Standardize sampling effort or use a method that accounts for unequal effort before comparing.
Carta 533
Domanda
How does acclimation differ from adaptation?
Risposta
Acclimation occurs within an individual; adaptation is an inherited population change across generations.
Carta 534
Domanda
How can removal of a top predator affect lower trophic levels?
Risposta
It can trigger a trophic cascade by changing prey abundance and the organisms prey consume.
Carta 535
Domanda
Why can extra fertilizer cause low oxygen in water?
Risposta
Nutrient enrichment drives algal growth; decomposition then consumes dissolved oxygen.
Carta 536
Domanda
What does a Type III survivorship curve show?
Risposta
High early mortality with much better survival among those reaching later stages.
Carta 537
Domanda
How can predation maintain diversity?
Risposta
A predator can prevent one strong competitor from dominating the community.
Carta 538
Domanda
How can disturbance increase or decrease diversity?
Risposta
Its effect depends on frequency and intensity; it may create habitat variety or eliminate sensitive species.
Carta 539
Domanda
Why protect multiple habitats rather than one small reserve?
Risposta
Different habitats, disturbances, and climate trajectories preserve more species and ecological options.
Carta 540
Domanda
A restoration site gains species but not nutrient cycling. How should success be evaluated?
Risposta
Use both composition and ecosystem-function measures; one metric alone gives an incomplete result.
540 carte
AP Biology Flashcards: Complete 8-Unit Course Review
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