Amino Acids, Peptides, and Proteins

Question 1

All chiral amino acids used in eukaryotes are…

Answer 1

L-amino acids, which means NH3 is on the left side of Fisher Projection

Question 2

Exception to (S) absolute configuration

Answer 2

cysteine (R group has higher priority)

Question 3

Nonpolar and nonromantic

Answer 3

glycine
alanine
leucine
valine
isoleucine 
methionine 
proline

Question 4

Aromatic side chain

Answer 4

tryptophan
tyrosine
phenylalanine

Question 5

Polar side chains

Answer 5

serine
threonine 
asparagine
glutamine
cysteine

Question 6

Acidic side chains

Answer 6

Glutamate and Aspartate (negatively charged at physiological pH)

Question 7

Basic side chains

Answer 7

Lysine
arginine
histidine

Question 8

Type of ring on histidine

Answer 8

imidazole –> aromatic ring with two nitrogens

Question 9

If pH is < pKa

Answer 9

protonated form predominates

Question 10

pKa for COOH

Answer 10

around 2

Question 11

pKa doe NH2

Answer 11

around 9

Question 12

isoelectric point

Answer 12

pH at which the molecule is electrically neutral

Question 13

pI neutral amino acid

Answer 13

pKa NH + pKa COOH / 2

Question 14

pI acidic amino acid

Answer 14

pKa R group + pKa COOH / 2

R group is COOH (acidic)

Question 15

peptide bonds

Answer 15

condensation, dehydration, acyl substitution reaction

partial double bond character

Question 16

chymotrypsin

Answer 16

cleaves COOH end of Phe, Trp, Tyr

Question 17

trypsin

Answer 17

cleaves COOH end of Lys, Arg

Question 18

general way in which enzymes break peptide bonds:

Answer 18

add H to the amino group and OH to carbonyl carbon

Question 19

alpha helices

Answer 19

rodlike structure in which chain coils clockwise.
stabilized by H-bonds between carbonyl O and amide H
R groups point away from core

Question 20

proline in secondary structures

Answer 20

found in the turns of beta-sheets and as the residue at the start of alpha helix

Question 21

disulfide bonds

Answer 21

important in tertiary structures

forms between cysteine molecules that become oxidized to form cystine

Question 22

conjugated protein

Answer 22

derive part of their function from covalently attached molecules called prosthetic groups (vitamins, metal ions,)

Question 23

what can cause protein denaturation?

Answer 23

temperature
urea
detergents (SDS)