Amino Acid Side-Chain Properties Flashcards: Polarity & Charge
56 flashcards on amino acid side-chain groups, charge at pH 7, and common property distinctions, with supplied-pKa reasoning and key exceptions.
ഈ ഡെക്കിനെക്കുറിച്ച്
Practice amino acid side-chain properties with 56 original flashcards for learners who already recognize the 20 standard amino-acid names. The cards ask you to recall a named amino acid’s property group, identify an amino acid or a specified set from a functional-group clue, distinguish commonly confused properties, and infer predominant side-chain charge from supplied pH and pKa values.
The reference pH is 7. Charge means the R group alone, excluding backbone groups and peptide termini. Ordinary charge statements use a simple aqueous reference model, not a guarantee about a particular site inside a protein. The calculations supply their pKa assumptions; one cysteine example changes the pH to 9.3, and one histidine example supplies a shifted local pKa. You do not need to memorize exact pKa values.
This deck uses a four-group study convention: nonpolar (glycine, alanine, valine, leucine, isoleucine, methionine, proline, phenylalanine, tryptophan); polar and predominantly uncharged at pH 7 (serine, threonine, asparagine, glutamine, cysteine, tyrosine); acidic (aspartate, glutamate); and basic (lysine, arginine, histidine). These are broad labels. Tryptophan has a polar hydrogen-bond donor; cysteine can behave hydrophobically; tyrosine is both aromatic and polar. Histidine belongs to the basic family but is mostly neutral at pH 7 when its side-chain pKa is 6.0. Aromaticity, polarity, and charge are not mutually exclusive descriptors.
The sequence starts with charge scope and classification, introduces the 20 amino acids in an interleaved order, then moves through property clues, comparisons, and pH reasoning. Related recall directions are separated so a nearby answer is less likely to give away the next one. Glycine’s flexibility, proline’s ring and backbone donor exception, cysteine’s disulfides, aromatic side chains, and acid-versus-amide distinctions receive focused practice.
The deck does not test one-letter or three-letter codes, structure drawings, exact pKa memorization, pI calculations, codons, dietary requirements, clinical decisions, or full-course/exam coverage. Broad clues are only reversed when the requested answer is a clear amino acid or an explicitly requested set. Structure and code recognition are covered separately in the amino acid structures and codes deck.
The questions, answers, examples, sequence, and metadata were independently authored from common biochemical facts. Fact checks used EMBL-EBI’s side-chain chemistry and ionisation guidance, plus ChEBI’s chemical classification. No source passages, exercises, or diagrams were copied. The cover is an original AI-generated conceptual illustration, not a chemical model.
Original text, organization, metadata, and generated cover are offered under CC0 1.0 to the extent applicable rights exist. This dedication does not cover source materials or anyone else’s rights. This is an independent study resource, not affiliated with or endorsed by EMBL-EBI or any course or examination provider.
ഈ ഡെക്കിലെ കാർഡുകൾ
കാർഡ് 1
ചോദ്യം
When a card asks for an amino acid’s side-chain charge, which charges should you leave out?
ഉത്തരം
The backbone amino and carboxyl groups, including peptide termini. Count only the R group’s charge.
കാർഡ് 2
ചോദ്യം
Can an uncharged amino-acid side chain still be polar?
ഉത്തരം
Yes. Uneven electron distribution can make a group polar without giving it a net charge; a hydroxyl group is an example.
കാർഡ് 3
ചോദ്യം
Are ‘aromatic,’ ‘polar,’ and ‘basic’ mutually exclusive amino-acid labels?
ഉത്തരം
No. They describe different features. A ring can be aromatic while another feature makes the side chain polar or basic. Group labels are a study convention, not an exhaustive chemical description.
കാർഡ് 4
ചോദ്യം
Alanine side chain → polarity group?
ഉത്തരം
Nonpolar. Its methyl group has no polar functional group.
കാർഡ് 5
ചോദ്യം
Serine side chain at pH 7 → polarity/charge group?
ഉത്തരം
Polar, predominantly uncharged. It contains a hydroxyl group.
കാർഡ് 6
ചോദ്യം
Aspartate side chain at pH 7 → acid/base group and predominant charge?
ഉത്തരം
Acidic; −1. The side-chain carboxyl group is predominantly deprotonated under the usual aqueous reference conditions.
കാർഡ് 7
ചോദ്യം
Valine side chain → polarity group?
ഉത്തരം
Nonpolar. It is a branched hydrocarbon side chain.
കാർഡ് 8
ചോദ്യം
Glutamine side chain at pH 7 → polarity/charge group?
ഉത്തരം
Polar, uncharged. Its amide group does not behave like glutamate’s carboxylate.
കാർഡ് 9
ചോദ്യം
Lysine side chain at pH 7 → acid/base group and predominant charge?
ഉത്തരം
Basic; +1. Its terminal side-chain amino group is predominantly protonated under the usual aqueous reference conditions.
കാർഡ് 10
ചോദ്യം
Phenylalanine side chain → polarity group?
ഉത്തരം
Nonpolar. Its benzyl group contains an aromatic ring.
കാർഡ് 11
ചോദ്യം
Glycine → polarity group in this deck’s convention?
ഉത്തരം
Nonpolar. Its R group is just hydrogen; the grouping does not imply a large hydrophobic side chain.
കാർഡ് 12
ചോദ്യം
Threonine side chain at pH 7 → polarity/charge group?
ഉത്തരം
Polar, predominantly uncharged. Its hydroxyl group contributes polarity despite the methyl group beside it.
കാർഡ് 13
ചോദ്യം
Glutamate side chain at pH 7 → acid/base group and predominant charge?
ഉത്തരം
Acidic; −1. Its side-chain carboxyl group is predominantly deprotonated under the usual aqueous reference conditions.
കാർഡ് 14
ചോദ്യം
Leucine side chain → polarity group?
ഉത്തരം
Nonpolar. It is a branched hydrocarbon side chain.
കാർഡ് 15
ചോദ്യം
Cysteine at pH 7 → group in this deck’s convention?
ഉത്തരം
Polar, predominantly uncharged. The side-chain thiol is usually mostly protonated. Cysteine can also behave hydrophobically, so classification schemes differ.
കാർഡ് 16
ചോദ്യം
Arginine side chain at pH 7 → acid/base group and predominant charge?
ഉത്തരം
Basic; +1. The guanidinium group is predominantly protonated under the usual aqueous reference conditions.
കാർഡ് 17
ചോദ്യം
Tryptophan → polarity group in this deck’s convention?
ഉത്തരം
Nonpolar overall, with a polar feature. Its large aromatic indole group is hydrophobic, but its N–H can donate a hydrogen bond.
കാർഡ് 18
ചോദ്യം
Proline → polarity group in this deck’s convention?
ഉത്തരം
Nonpolar. Its side chain also closes a ring with the backbone nitrogen, restricting backbone motion.
കാർഡ് 19
ചോദ്യം
Asparagine side chain at pH 7 → polarity/charge group?
ഉത്തരം
Polar, uncharged. Its amide group is distinct from aspartate’s carboxylate.
കാർഡ് 20
ചോദ്യം
Isoleucine side chain → polarity group?
ഉത്തരം
Nonpolar. It is a branched hydrocarbon side chain.
കാർഡ് 21
ചോദ്യം
Histidine → acid/base family?
ഉത്തരം
Basic. Its imidazole can accept a proton. ‘Basic’ does not mean mostly +1 at pH 7: with a side-chain pKa of 6.0, most molecules have a neutral side chain.
കാർഡ് 22
ചോദ്യം
Tyrosine at pH 7 → group in this deck’s convention?
ഉത്തരം
Polar, predominantly uncharged. Its phenolic hydroxyl adds polarity to an aromatic, partly hydrophobic side chain; other schemes group it with the aromatics.
കാർഡ് 23
ചോദ്യം
Methionine side chain → polarity group?
ഉത്തരം
Nonpolar overall. Its sulfur is part of a thioether, not a thiol.
കാർഡ് 24
ചോദ്യം
Which standard amino acid has hydrogen as its R group and no chiral alpha carbon?
ഉത്തരം
Glycine. Its small R group also permits more backbone conformations than most residues.
കാർഡ് 25
ചോദ്യം
Which two standard amino acids have side-chain amide groups?
ഉത്തരം
Asparagine and glutamine. Their amides are polar and uncharged at pH 7.
കാർഡ് 26
ചോദ്യം
For a single ionizable side-chain group, what does pH below its pKa favor?
ഉത്തരം
The protonated form. Whether that form is neutral or positive depends on the group.
കാർഡ് 27
ചോദ്യം
Which two standard amino acids have aliphatic alcohol side chains?
ഉത്തരം
Serine and threonine. Tyrosine’s hydroxyl is phenolic, attached directly to an aromatic ring.
കാർഡ് 28
ചോദ്യം
Which standard amino acid supplies the side-chain sulfur atoms of a protein disulfide bond?
ഉത്തരം
Cysteine. Oxidation of two cysteine thiols can produce a covalent S–S link.
കാർഡ് 29
ചോദ്യം
Which three standard amino acids are conventionally called the branched-chain amino acids?
ഉത്തരം
Valine, leucine, and isoleucine. All three have nonpolar hydrocarbon side chains.
കാർഡ് 30
ചോദ്യം
Which two standard amino acids usually have negatively charged side-chain carboxylates at pH 7?
ഉത്തരം
Aspartate and glutamate.
കാർഡ് 31
ചോദ്യം
Which standard amino acid closes its side chain back onto the backbone nitrogen?
ഉത്തരം
Proline. The ring restricts backbone flexibility; an internal proline residue also lacks the usual peptide N–H donor.
കാർഡ് 32
ചോദ്യം
For a single ionizable side-chain group, what is the protonated:deprotonated ratio at pH = pKa?
ഉത്തരം
1:1. Half is protonated and half is deprotonated in the simple two-state acid–base model.
കാർഡ് 33
ചോദ്യം
Which three standard amino acids form the usual ‘aromatic amino acids’ study group?
ഉത്തരം
Phenylalanine, tyrosine, and tryptophan. Histidine’s imidazole is chemically aromatic too, but introductory grouping tables usually place histidine with the basic amino acids.
കാർഡ് 34
ചോദ്യം
Cysteine versus methionine: which side chain can make the usual protein disulfide link?
ഉത്തരം
Cysteine. It has a thiol; methionine has a thioether and does not form this cysteine-type disulfide link.
കാർഡ് 35
ചോദ്യം
For a single ionizable side-chain group, what does pH above its pKa favor?
ഉത്തരം
The deprotonated form. For a carboxyl group this is negative; for a protonated amine losing its proton, it is neutral.
കാർഡ് 36
ചോദ്യം
At pH 7, why is aspartate usually charged while asparagine is uncharged?
ഉത്തരം
Aspartate has a side-chain carboxylate (−1); asparagine has a neutral amide. Similar names do not mean the same functional group.
കാർഡ് 37
ചോദ്യം
Which standard amino acid has an imidazole side chain that can switch between neutral and +1 forms?
ഉത്തരം
Histidine. Its protonation depends on pH and its local pKa.
കാർഡ് 38
ചോദ്യം
Which standard amino acid combines a phenyl ring with a phenolic hydroxyl group?
ഉത്തരം
Tyrosine. The hydroxyl makes this aromatic side chain more polar than phenylalanine’s.
കാർഡ് 39
ചോദ്യം
Glycine versus proline: which generally allows more backbone conformations?
ഉത്തരം
Glycine. Its tiny R group imposes little steric restriction; proline’s ring constrains the backbone.
കാർഡ് 40
ചോദ്യം
Why can tryptophan donate a side-chain hydrogen bond despite being grouped as nonpolar overall?
ഉത്തരം
Its indole N–H can donate a hydrogen bond. A large hydrophobic group can still contain a polar site.
കാർഡ് 41
ചോദ്യം
Must every nonpolar side chain lie inside a water-soluble globular protein?
ഉത്തരം
No. Burial of nonpolar groups is a tendency, not a rule for every residue. Protein shape and local interactions also matter.
കാർഡ് 42
ചോദ്യം
Assume histidine’s side-chain pKa is 6.0. At pH 7.0, is its predominant side-chain charge 0 or +1?
ഉത്തരം
0
pH is one unit above pKa, so neutral:protonated is 10:1; about 9% is +1. This is a supplied-pKa model, not a universal protein value.
കാർഡ് 43
ചോദ്യം
Assume cysteine’s thiol pKa is 8.3. At pH 7.0, which form predominates: neutral thiol or negative thiolate?
ഉത്തരം
Neutral thiol. pH is below pKa, so the protonated S–H form predominates.
കാർഡ് 44
ചോദ്യം
At pH 7, which has a predominantly −1 side chain: glutamate or glutamine?
ഉത്തരം
Glutamate. Glutamine’s side-chain amide is neutral.
കാർഡ് 45
ചോദ്യം
Assume tyrosine’s phenolic pKa is 10.1. At pH 7.0, is its side chain predominantly neutral or negative?
ഉത്തരം
Neutral. The phenolic hydroxyl is mostly protonated because pH is below pKa.
കാർഡ് 46
ചോദ്യം
Assume lysine’s side-chain pKa is 10.5. At pH 7.0, is its side chain predominantly neutral or +1?
ഉത്തരം
+1. pH is below pKa, favoring the protonated amino group.
കാർഡ് 47
ചോദ്യം
Assume aspartate’s side-chain pKa is 3.9. At pH 7.0, is its side chain predominantly neutral or −1?
ഉത്തരം
−1. pH is above pKa, favoring the deprotonated carboxylate.
കാർഡ് 48
ചോദ്യം
Can a standard aqueous pKa value determine a buried protein side chain’s charge with certainty?
ഉത്തരം
No. Nearby charges, solvent exposure, and other local interactions can shift pKa. Use a value appropriate to that site when it is known.
കാർഡ് 49
ചോദ്യം
With a histidine side-chain pKa of 6.0, does the label ‘basic amino acid’ imply a predominantly +1 side chain at pH 7?
ഉത്തരം
No. ‘Basic’ describes proton-accepting chemistry; the predominant charge at a stated pH follows the pKa. Here the side chain is mostly neutral.
കാർഡ് 50
ചോദ്യം
Does a predominantly neutral tyrosine side chain at pH 7 make tyrosine nonpolar in this deck’s grouping?
ഉത്തരം
No. Its hydroxyl is polar even when uncharged. This deck groups tyrosine as polar, uncharged and also recognizes its aromatic character.
കാർഡ് 51
ചോദ്യം
Does an internal proline residue have the same backbone N–H hydrogen-bond donor as most peptide residues?
ഉത്തരം
No. Its backbone nitrogen has no attached hydrogen in the peptide chain. This is a backbone consequence of its ring, not a side-chain charge.
കാർഡ് 52
ചോദ്യം
At pH = pKa, a side chain switches between 0 and +1. Is each individual side chain charged +0.5?
ഉത്തരം
No. The two forms occur in equal proportions, giving an ensemble-average charge of +0.5. Each form still has charge 0 or +1.
കാർഡ് 53
ചോദ്യം
Assume cysteine’s thiol pKa is 8.3. At pH 9.3, what is its predominant side-chain charge?
ഉത്തരം
−1. Deprotonated thiolate predominates; the thiolate:thiol ratio is 10:1 in the simple model.
കാർഡ് 54
ചോദ്യം
At pH 7, which pair is a plausible side-chain salt bridge: lysine–glutamate or leucine–valine?
ഉത്തരം
Lysine–glutamate: their usual side-chain charges are +1 and −1. A salt bridge still requires suitable proximity and environment.
കാർഡ് 55
ചോദ്യം
A histidine site has a measured side-chain pKa of 8.0. At pH 7.0, which side-chain form predominates?
ഉത്തരം
The protonated +1 form. pH is below this site’s pKa; use the supplied local value rather than a generic histidine value.
കാർഡ് 56
ചോദ്യം
Phenylalanine versus tyrosine: which has the side-chain hydroxyl that adds polarity?
ഉത്തരം
Tyrosine. Phenylalanine lacks that hydroxyl; both contain an aromatic ring.
56 കാർഡുകൾ
Amino Acid Side-Chain Properties Flashcards: Polarity & Charge
പഠനം തുടങ്ങാൻ Nibomo തുറക്കും.