EXAM 2 multiple choice

Question 1

What does an α-amino acid consist of?
a) carbonyl group, α carbon, amino group, oxygen atom, distinctive R group
b) carboxylic acid group, α carbon, amino group, hydrogen atom, distinctive R group
c) carboxylic acid group, ε carbon, nitro group, hydrogen atom
d) alcohol group, α carbon, amino group, nitrogen atom, distinctive R group, hydrogen
atom
e) carboxylic acid group, δ carbon, imine radical, hydrogen atom, distinctive R group

Answer 1

b) carboxylic acid group, α carbon, amino group, hydrogen atom, distinctive R group

Question 2

What isomers of amino acids are found in proteins and what absolute configuration do they have?

a. L isomer; R absolute configuration
b. D and L isomers; R absolute configuration
c. L isomer; S absolute configuration
d. D isomer; S absolute configuration
e . L and D isomers; S absolute configuration

Answer 2

L isomer; S absolute configuration

Question 3

Which amino acid has the one-letter abbreviation K
a) histidine
b) asparagine
c) alanine
d) valine
e) Lysine

Answer 3

E . (LYSINE)

Question 4

What is the N-terminal amino acid and what is the C-terminal amino acid in the sequence of amino acids Gly-Tyr-Gly-Phe-Leu?
a) Leucine is N-terminal and glycine is C-terminal.
b) Glycine is N-terminal and leucine is C-terminal.
c) Tyrosine is N-terminal and leucine is C-terminal.
d) Phenylalanine is N-terminal and leucine is C-terminal.
e) There are no N-terminal and C-terminal residues in the sequences of amino acids.

Answer 4

b) Glycine is N-terminal and leucine is C-terminal.

Question 5

A protein with a molecular weight of 75,550 g/mol has a mass of
a) 75,550 Da or 755.5 kDa.
b) 7555 Da or 75.55 kDa
c) 75,550 Da or 75.55 kDa.
d) 755,500 Da or 7.555 kDa.
e) 7,555,000 Da or 75550 kDa.

Answer 5

c) 75,550 Da or 75.55 kDa.

Question 6

Choose atoms that lie in a plane of the peptide bond in a pair of linked amino acids.

A. Cα3, C, O, N, Cα2
B. Cα, C, N, H, Cα2
C. Cα, C, O, H, Cα3
D. Cα, Cα2, Cα3, N, H, C
E. Cα1, C, O, N, H, Cα2

Answer 6

E. Cα1, C, O, N, H, Cα2

Question 7

A protein quaternary structure is composed on multiple polypeptide chains called subunits. A dimer is protein composed of two polypeptide chains or two subunits. Hemoglobin is protein with four subunits. Hemoglobin is therefore a
a) dimer
b) tetramer
c) pentamer
d) subunit
e) peptide bond

Answer 7

b) tetramer

Question 8

What is the configuration of peptide bonds in proteins?

A. Almost all peptide bonds are in the cis configuration.
B. Almost all peptide bonds are in the trans configuration.
C.Half of all peptide bonds are in the trans configuration and the other half are in the
cis configuration.
D. Approximately one third are in the trans configuration and rest are in the cis
configuration.
E.Approximately one third are in the cis configuration and rest are in the trans
configuration.

Answer 8

B. Almost all peptide bonds are in the trans configuration.

Question 9

What is the name of the angle of rotation about the bond between the α carbon and the carbonyl carbon atoms that is used in Ramachandra plot?
a) α b) δ c) ε d) Ψ e) φ

Answer 9

d) Ψ
Free Rotation Varies From -180 degree to 180 Degree.

Question 10

What disrupts disulfide bonds in proteins?
a) guanidinium sulfide
b) β-mercaptoethanol
c) uric acid
d) urea
e) ammonia

Answer 10

B. B-mercaptoethanol

Question 11

What is the term for a molecule that contains both positive and negative charges but overall has a neutral charge?
a) enantiomer
b) amino acid
c) racemate
d) zwitterion
e) Amphipath

Answer 11

d) zwitterion, because Zwitter Ion has an overall neutral charge

Question 12

Which amino acid forms disulfide bonds?
a) histidine
b) methionine
c) proline
d) serine
e) cysteine

Answer 12

e cysteine

Question 13

what level of protein structure is composed of α helices, β sheets, and turns?
a) primary
b) secondary
c) tertiary
d) quaternary
e) All of above

Answer 13

b) secondary

Question 14

The overall three-dimensional structure of a single polypeptide is referred to as _____ structure.
a) primary
b) secondary
c) tertiary
d) quaternary
e) None of above

Answer 14

c) tertiary

Question 15

the term quaternary with respect to protein structure stands for:
a) a repeating structure stabilized by intrachain hydrogen bonds.
b)the ability to form all four kinds of noncovalent bonds
c) a multisubunit structure
d) a linear sequence of four amino acids.
e.) the only four amino acids that can form hydrogen bonds.

Answer 15

c) a multisubunit structure

Question 16

Which of the following peptides would absorb light at 280 nm?
a. Ala-Lys-His
b. Ser-Gly-Asn
c. Ala-Ala-Trp
d. Val-Pro-Leu
e. Ser-Val-Ile

Answer 16

c. Ala-Ala-Trp

Question 17

what reagent would reduce the disulfide bonds found in insulin?

Answer 17

dithiothreitol reagent

Question 18

two amino acids that contain sulfur

Answer 18

methionine & cysteine

Question 19

proteins absorb uv as the result of 3 amino acids
at what wave length ?

Answer 19

try, try, & phe
280

Question 20

one amino acid loses an oxygen and hydrogen atom from its _______ the other loses an atom from its ______

Answer 20

carboxyl group
amino group

Question 21

in protein purification techniques what sds - page stands for ?

Answer 21

sodium dodecyl sulfate

Question 22

during protein purification, cell must be broken down and disrupted using

Answer 22

high concentration of chemicals