MCB 450 EXAM 3 PRE-LECTURE AND HOMEWORK UPDATED ACTUAL QUESTIONS AND CORRECT ANSWERS

MCB 450 EXAM 3 PRE-LECTURE AND HOMEWORK
UPDATED ACTUAL QUESTIONS AND CORRECT
ANSWERS

Question:
1. Which of the following best describes the Km of an enzymatic reaction?
a. How much substrate inhibits the enzyme by 50%
b. The concentration of substrate needed to reach the Vmax
c. The rate at which the substrate binds the enzyme
d. The concentration of substrate needed to reach ½ the Vmax
e. The amount of enzyme needed to consume all the substrate
Answer:
d. The concentration of substrate needed to reach ½ the Vmax

Question:
2. Which of the following is true about the transition state of an enzymatic reaction?
a. The transition state is the most abundant species along the reaction pathway
b. The state when the molecule being modified by the enzyme is neither the original substrate nor final
product
c. The difference in free energy between the transition state and the substrate is called the free energy of
the reaction
d. When the transition energy is lowered, there are fewer molecules that will become the final product
e. The energy of activation is added to the free energy of the reaction
Answer:
b. The state when the molecule being modified by the enzyme is neither the original substrate nor final
product

Question:
3. Carbohydrates are less-efficient fuel sources than fats because the carbon in carbohydrates is more:
a. positively charged
b. oxidized
c. acidic
d. basic
e. saturated
Answer:
b. oxidized

Question:
4. Which of the following carries a hydride in catabolic pathways?
a. FAD
b. FADH2
c. ADP
d. NADH
e. Biotin

, Answer:
d. NADH

Question:
5. Which of the following statements about integral membrane lipids is FALSE?
a. Lipids head groups are hydrophobic.
b. They have a polar headgroup that interacts with water.
c. Lipids in a bilayer rapidly diffuse laterally.
d. Lipid bilayers are highly impermeable.
e. They have hydrophobic hydrocarbon tails that repel water.
Answer:
a. Lipids head groups are hydrophobic.

Question:
6. Which of the following statements about membrane transport is True?
a. Membrane transport proteins make many strong, covalent interactions with their polar substrates, and
these replace solute-water interactions.
b. ATP is never used to pump material across the membrane.
c. There is no energy barrier to the transport of charged or polar solutes across a cell membrane.
d. If a solute crosses a cell membrane through an active transport it will move across the bilayer until the
concentration gradient reaches an equilibrium.
e. Solutes that cross a cell membrane by facilitated or passive diffusion will move down a concentration
gradient.
Answer:
e. Solutes that cross a cell membrane by facilitated or passive diffusion will move down a concentration
gradient.

Question:
7. In a metabolic pathway, a reaction that best serves as a committed step:
a. Is metabolically irreversible.
b. Is shared amongst at least two pathways.
c. Follows Michaelis-Menten kinetics.
d. Can be easily reversible.
e. Has a large positive ∆G.
f. Is a near equilibrium reaction.
Answer:
a. Is metabolically irreversible.

Question:
8. The electrons released during oxidation reactions cannot be captured by:
a. FMN
b. NAD+
c. All of the above molecules can capture electrons
Answer:
c. All of the above molecules can capture electrons