Significant Structures

Question 1

Methionine (Met, M)

Answer 1

Sulfur atom (S) in the side chain

Question 2

Tryptophan (Try, W)

Answer 2

Indole ring attached to alanyl side chain

Question 3

Phenylalanine (Phe, F)

Answer 3

Phenyl group attached to alanine

Question 4

Proline (Pro, P)

Answer 4

Does not have a free alpha-amino group
Side chain is a cyclic structure

Question 5

Serine (Ser, S)

Answer 5

Aliphatic hydroxyl group (-OH)
Subject to phosphorylation (post translational modification)

Question 6

Cysteine (Cys, C)

Answer 6

Sulfur atom (S) in the side chain

Question 7

Asparagine (Asn, N)

Answer 7

Amide in the side group

Question 8

Glutamine (Gln, Q)

Answer 8

Amide in the side chain

Question 9

Threonine (Thr, T)

Answer 9

Aliphatic hydroxyl group (-OH)
Subject to phosphorylation (post translational modification)

Question 10

Tyrosine (Tyr, Y)

Answer 10

Phenol Derivative
Possesses a hydroxyl group (-OH) in the aromatic ring

Question 11

Aspartic Acid, Aspartate (Asp, D)

Answer 11

Carboxylic acid (-COOH) on side chain
Present in metal-binding sites on metalloproteins

Question 12

Glutamic acid, Glutamate (Glu, E)

Answer 12

Carboxylic acid (-COOH) on side chain
Present in metal-binding sites on metalloproteins

Question 13

Arginine (Arg, R)

Answer 13

Guanidino group in side chain is the most basic of all R groups (pKa = 12.5)

Question 14

Histidine (His, H)

Answer 14

This amino acid has buffering capacity at physiological pH
Imidazole side chain allows the amino acid to function in both acid and base catalysis at physiological pH
pKa of imidazole side chain = 6.0
Most often found in the active sites of protein enzymes