Amino Acids and Peptides

Question 1

pI

Answer 1

isoelectric point - pH at which compound has no net charge; (sum of 2 acidic/basic pk’s)/2

Question 2

Aliphatic a.a.s

Answer 2

Gly, Ala, Leu, Ile, Val

Question 3

Hydroxyl a.a.s

Answer 3

Ser, Thr, Tyr

Question 4

Sulfidryl a.a.s

Answer 4

Met, Cys, Sec (has Se)

Question 5

Acidic a.a.s w/ their amides

Answer 5

Asp - Asn, Glu - Gln

Question 6

Basic a.a.s

Answer 6

Arg, Lys, His

Question 7

Aromatic a.a.s & i.a.

Answer 7

Phe, Tyr, Trp, His, Pro

Question 8

Gly

Answer 8

Glycine -H

Question 9

Ala

Answer 9

Alanine -CH3

Question 10

Val

Answer 10

Valine -CH-CH3
l
CH3

Question 11

Leu

Answer 11

Leucine -CH2-CH-CH3
l
CH3

Question 12

Ile

Answer 12

Isoleucine -CH-CH2-CH3
l
CH3

Question 13

Ser

Answer 13

Serine -CH2-OH

Question 14

Thr

Answer 14

Threonine -CH-CH3
l
OH

Question 15

Tyr

Answer 15

Tyrosine -CH2-aromatic 6C ring-OH

Question 16

Cys

Answer 16

Cysteine -CH2-SH

Question 17

Met

Answer 17

Methionine -CH2-CH2-S-CH3

Question 18

Sel

Answer 18

Selenocysteine -CH2-HSe

Question 19

Asp

Answer 19

Aspartic acid -CH2-COO^-

Question 20

Asn

Answer 20

Asparagine -CH2-C=O
l
NH2

Question 21

Glu

Answer 21

Glutamic acid -CH2-CH2-COO^-

Question 22

Gln

Answer 22

Glutamine -CH2-CH2-C=O
l
NH2

Question 23

Arg

Answer 23

Arginine -CH2-CH2-CH2-NH
l
C=NH2+
l
NH2

Question 24

Lys

Answer 24

Lysine -CH2-CH2-CH2-CH2-NH3+

Question 25

His

Answer 25

Histidine -CH2-ring 5member with 2 N’s

Question 26

Phe

Answer 26

Phenylalanine -CH2-aromatic 6C ring

Question 27

Trp

Answer 27

Tryptophan -CH2-joined 5member ring w/ aromatic 6C ring

Question 28

Pro

Answer 28

Proline

imino ring

Question 29

strongest chromophores?

Answer 29

Trp and Tyr

Question 30

Nonpolar a.a.

Answer 30

Aliphatic: Gly, Ala, Leu, Ile, Val
Aromatic: Phe, Tyr, Trp, His

Question 31

Polar a.a.

Answer 31

Polar: Asn, Gln, Pro
Hydroxyl: Ser, Thr, Tyr
Charged: Arg, Lys, Asp, Glu, His
Sulfur-containing: Met, Cys, Sec

Question 32

Which a.a. is not optically active?

Answer 32

Gly

Question 33

Covalent bonds in proteins:

Answer 33

peptide bonds, disulfide bonds

Question 34

Non-covalent bonds in proteins:

Answer 34

ionic bonds / electrostatic interactions, H-bonds, Hydrophobic interactions, Van Der Waals forces

Question 35

Glutathione

Answer 35

peptide of glutamic acid, cysteine, and glycine

bond btwn Glu and Cys is in Glu’s carboxyl in the R chain instead of at the a-carbon

antioxidant; prevents damage to important cell components caused by reactive oxygen species such as free radicals and peroxides

Question 36

Which group in glutathione is continuously reduced and oxidized?

Answer 36

The sulfhydryl group in Cys

Question 37

pk2’s of a.a.s

Answer 37

8.8 to 10.8

Question 38

pk1’s of a.a.s

Answer 38

1.8 to 2.4

Question 39

a.a.s with pk3’s around 13

Answer 39

Ser, Thr, Arg (12.5)

Question 40

a.a.s with pk3’s around 10

Answer 40

Tyr, Lys, Cys (8.3)

Question 41

a.a. with pk3 of 6

Answer 41

His

Question 42

a.a.s with pk3 around 4

Answer 42

Asp, Glu