Chapter 1 - Amino Acids, Peptides, and Proteins

Question 1

Structure of an amino acid

Answer 1

• carboxyl group, amino group (NH2), a hydrogen, and an R group, all attached to an alpha carbon

Question 2

Which amino acid is achiral?

Answer 2

• Glycine (R group is an H)

Question 3

What is the one chiral amino acid that is in R configuration instead of S?

Answer 3

• Cysteine (R group is a CH2SH group and takes priority over carboxyl group)

Question 4

Alanine R-group

Answer 4

• 1 Carbon
• A (Ala)

Question 5

Valine R-group

Answer 5

• 2 Carbons
• V (Val)

Question 6

Leucine R-group

Answer 6

• 3 Carbons
• L (Leu)

Question 7

Isoleucine R-group

Answer 7

• 4 Carbons
• I (Ile)

Question 8

Methionine R-group

Answer 8

• 2 Carbons, S, then another Carbon
• M (Met)

Question 9

Proline R-group

Answer 9

• forms cyclic amino acid
• nitrogen becomes part of a 5-membered ring ( 3 Carbons in R-group)
• P (Pro)

Question 10

Tryptophan R-group

Answer 10

• double ring system including another nitrogen
• W (Trp)

Question 11

Phenylalanine R-group

Answer 11

• benzyl group (benzene ring + CH2 group)
• F (Phe)

Question 12

Tyrosine R-group

Answer 12

• benzyl group (benzene ring + CH2 group) + Hydroxyl group off the ring
• Y (Tyr)

Question 13

Serine R-group

Answer 13

• two carbons + hydroxyl group
• hydroxyl group is on tertiary carbon
• S (Ser)

Question 14

Threonine R-group

Answer 14

• two carbons + hydroxyl group
• hydroxyl group is on first carbon of R group
• T (Thr)

Question 15

Asparagine R-group

Answer 15

• amide group and 1 carbon
• N (Asn)

Question 16

Glutamine R-group

Answer 16

• amide group and 2 carbons
• Q (Gln)

Question 17

Cysteine R-group

Answer 17

• thiol group (SH) and 1 carbon
• C (Cys)

Question 18

Aspartate

Answer 18

• 1 carbon and a carboxylate (COO-)
• D (Asp)

Question 19

Glutamate

Answer 19

• 2 carbons and a carboxylate group (COO-)
• E (Glu)

Question 20

Lysine R-group

Answer 20

• terminal primary amino group
• K (Lys)

Question 21

Arginine R-group

Answer 21

• has 3 nitrogens in side chain
• R (Arg)

Question 22

Histidine R-group

Answer 22

• aromatic ring with 2 nitrogen atoms
• H (His)

Question 23

Hydrophobic amino acids

Answer 23

• have long alkyl side chains
• alanine, isoleucine, leucine, valine, phenylalanine

Question 24

Hydrophilic amino acids

Answer 24

• charged side chains
• histidine, arginine, lysine (positively charged)
• glutamate and aspartate (negatively charged)