Biochemistry Exam Chapter 3

Question 1

The overall charge of the polypeptide His-Tyr-Lys-Ket-ILe-Glu at pH 6.9 is

Answer 1

0

Question 2

All amino acids derived from proteins have the same stereochemical conformation as

Answer 2

L-Glyceraldehyde

Question 3

At a ph above it’s pKa, the phenolic group of tyrosine is

Answer 3

deprotonated and negatively charged

Question 4

At a pH above its pKa, the e amino acid of lysine is

Answer 4

deprotonated and neutral

Question 5

The amino acid_ is commonly phosphorylated.

Answer 5

Ser

Question 6

Which of the following amino acids is generally absent from an A helix?

Answer 6

Pro

Question 7

Which of the following best describes the peptide backbone in a B sheet?

Answer 7

highly extended

Question 8

In a protein, the most conformationally restricted amino acid is_ ; the least conformationally restricted is _

Answer 8

Pro;Gly

Question 9

Lysine can form a salt bridge by interacting with the side chain of _

Answer 9

Glu

Question 10

From B Sheets, the terms “parallel” and “antiparallel” refer to_

Answer 10

The direction of the associated peptide strands

Question 11

Noncovalent forces that stabilize protein structure include all of the followings except_.

Answer 11

disulfide bridges

Question 12

What level of protein structure is characterized by the three-dimensional structure of an entire polypeptide including all the amino acid side chains?

Answer 12

tertiary

Question 13

The disulfide bond between two cysteine molecules_

Answer 13

is a covalent bond form by oxidation