UNIT 2 EXAM - PRACTICE

Question 1

How does a catalyst affect the overall AG of a chemical reaction?

A. The reaction proceeds to equilibrium more quickly.
B. The reaction becomes more endergonic.
C. The reaction cannot proceed to equilibrium.
D. The reaction becomes more exergonic.
E. It has no effect.

Answer 1

E. It has no effect.

Question 2

A proposed mechanism for ester hydrolysis by a bacterial lipase is shown below. This reaction is composed of both an acylation step, and a deactivation step that regenerates the enzyme.

In this mechanism:
A. His156 acts as both an acid and a base during deacylation of the substrate
B. Water is essential for the acylation step
C. The transition states are not stabilized by the enzyme
D. Asp133 participates in covalent catalvsis
E. The ester is hydrolyzed by Asp 133.

Answer 2

A. His156 acts as both an acid and a base during deacylation of the substrate

Question 3

Serine 195 plays a key role in the catalysis mechanism of chymotrypsin. Which of the below mutations do you anticipate would have the smallest impact on chymotrypsin catalysis?

A. Mutation of Ser 195 to alanine
B. Mutation of serine 195 to glutamate
C. Mutation of serine 195 to glycine
D. Mutation of serine 195 to cysteine
E. Mutation of serine 195 to tryptophan

Answer 3

D. Mutation of serine 195 to cysteine

Question 4

Enzymes catalyze reaction rates faster than 1,000,000 rxns per sec because…?

A. Enzymes become unstable when working so quickly.
B. substrates and products cannot diffuse in/out of the active site any faster than this.
C. reactions faster than this speed break the Levinthal paradox.
D. enzyme conformational changes cannot happen any faster.
E. this is the maximum speed that any chemical reaction can occur.

Answer 4

B. substrates and products cannot diffuse in/out of the active site any faster than this.

Question 5

If an enzyme-catalyzed reaction has a max of 20 mM/min, and a velocity of 2 mM/min when the substrate concentration is 1 mM, what is the Km?

A. 0.2 mM
B. 0.5 mM
C. 15 mM
D. 20 mM
E. 9 mM

Answer 5

E. 9 mM

Question 6

Membrane fluidity increases with __________ fatty acid chain length and _______ degree of fatty acid unsaturation.

A. longer; higher
B. longer; lower
C. shorter, higher
D. shorter; lower
E. fatty acids have no effect on membrane fluidity

Answer 6

C. shorter, higher

Question 7

Which statement about this human milk oligosaccharide is FALSE?

A. This oligosaccharide is a reducing sugar.
B. This oligosaccharide promotes the development of a healthy human microbiome.
C. All three component saccharides are hexoses.
D. This oligosaccharide can be readily used by humans to produce energy.

Answer 7

D. This oligosaccharide can be readily used by humans to produce energy.

Question 8

Identify a similarity shared among amylopectin, amylose, cellulose, and glycogen:

A. All four polysaccharides are linked via a-glycosidic bonds.
B. All four polysaccharides are made of glucose.
C. All four polysaccharides are found in plants.
D. All four polysaccharides can form branched structures.

Answer 8

B. All four polysaccharides are made of glucose.

Question 9

Which polysaccharide does NOT contribute to the increase of blood sugar level?

A. Amylopectin
B. Amylose
C. Cellulose
D. Glycogen

Answer 9

C. Cellulose

Question 10

Acarbose, an a-Glucosidase inhibitor, is used to treat type 2 diabetes, because

A. Acarbose inhibits amylase and maltase, preventing the release of glucose from starch, such as amylopectin and amylose.
B. Acarbose inhibits glycogen phosphorylase, preventing the release of glucose from liver.
C. Acarbose inhibits glycogen phosphorylase, preventing the release of glucose from skeletal muscles.
D. Acarbose inhibits the digestion of cellulose, preventing the release of glucose from a carbohydrate rich diet.

Answer 10

A. Acarbose inhibits amylase and maltase, preventing the release of glucose from starch, such as amylopectin and amylose.