Amino Acids Descriptions

Set of flashcards covering key concepts related to pKa values in molecular biology and amino acids

pKa

The negative logarithm of the acid dissociation constant, indicating the strength of an acid.

Influence of Local Environment on pKa

The pKa value can vary based on the local environment surrounding a functional group.

Approximate pKa values mentioned

The approximate pKa values include ~12, ~4, ~8, ~6, and ~10.

Significance of pKa

Understanding pKa values is crucial in predicting the behavior of acid-base reactions in biological systems.

pKa

The negative logarithm of the acid dissociation constant (pK{a} = -\log{10}(K_{a})), indicating the strength of an acid.

Influence of Local Environment on pKa

The pK_{a} value can vary based on the local environment surrounding a functional group, such as nearby charges or hydrophobic pockets.

Approximate pKa values mentioned

The approximate side-chain pK_{a} values include \sim 12 (Arg), \sim 4 (Asp/Glu), \sim 8 (Cys), \sim 6 (His), and \sim 10 (Lys/Tyr).

Significance of pKa

Understanding pK_{a} values is crucial in predicting the ionization state and behavior of acid-base reactions in biological systems.

Alanine (Ala, A)

A nonpolar, aliphatic amino acid with a simple methyl (-CH_{3}) side chain.

Arginine (Arg, R)

A positively charged (basic) amino acid with a guanidinium side chain; side chain pK_{a} \approx 12.5.

Asparagine (Asn, N)

A polar, uncharged amino acid with an amide functional group in its side chain.

Aspartic Acid (Asp, D)

A negatively charged (acidic) amino acid with a carboxylate side chain; side chain pK_{a} \approx 3.9.

Cysteine (Cys, C)

A polar amino acid containing a thiol (-SH) group; side chain pK_{a} \approx 8.3; capable of forming disulfide bonds.

Glutamine (Gln, Q)

A polar, uncharged amino acid with a side chain amide group, similar to Asparagine but with an extra methylene group.

Glutamic Acid (Glu, E)

A negatively charged (acidic) amino acid with a carboxylate side chain; side chain pK_{a} \approx 4.2.

Glycine (Gly, G)

The simplest amino acid, having only a hydrogen atom as its side chain; often found in flexible regions of proteins.

Histidine (His, H)

A basic amino acid with an imidazole side chain; side chain pK_{a} \approx 6.0, allowing it to act as a buffer near physiological pH.

Isoleucine (Ile, I)

A nonpolar, aliphatic amino acid with a branched side chain that is an isomer of Leucine.

Leucine (Leu, L)

A nonpolar, aliphatic amino acid with a branched side chain; frequently found in the hydrophobic core of proteins.

Lysine (Lys, K)

A positively charged (basic) amino acid with a primary amino group at the end of its side chain; side chain pK_{a} \approx 10.5.

Methionine (Met, M)

A nonpolar, sulfur-containing amino acid with a thioether group; often the first amino acid in a polypeptide chain.

Phenylalanine (Phe, F)

A nonpolar, aromatic amino acid with a phenyl ring attached to a methyl group.

Proline (Pro, P)

A nonpolar amino acid with a unique cyclic structure where the side chain bonds to the backbone nitrogen, introducing structural rigidity.

Serine (Ser, S)

A polar, uncharged amino acid with a hydroxyl (-OH) group; often involved in phosphorylation and catalysis.

Threonine (Thr, T)

A polar, uncharged amino acid with a secondary hydroxyl group; one of the two amino acids with two chiral centers.

Tryptophan (Trp, W)

A nonpolar, aromatic amino acid with a bulky indole side chain; the largest of the standard amino acids.

Tyrosine (Tyr, Y)

A polar, aromatic amino acid with a phenol side chain; side chain pK_{a} \approx 10.1.

Valine (Val, V)

A nonpolar, aliphatic amino acid with a branched isopropyl side chain.