Question

Multiple Choice

(1) When energy derived from ATP hydrolysis is coupled to an endergonic enzymatic reaction, which of the following is the most likely mechanistic description of this coupling?

a. ATP binds at a regulatory site and puts the enzyme in a more active conformation.

b. ATP binds at one active site of the enzyme and the substrate(s) bind at another.

c. Hydrolysis of ATP provides the energy for the endergonic reaction at the active site where the substrate(s) are bound.

d. ATP and substrate compete for binding to the same active site.

(2) End product feedback inhibition of multistep pathways is a major mechanism for cellular regulation. In this proccess, the

a. product of the last enzyme inhibits the substrate of the last enzyme.

b. product of an early metabolically irreversible enzyme inhibits the last enzyme in the pathway.

c. An early regulatory enzyme in the pathway is inhibited when ATP concentrations are depleted.

d. product of one of the last enzymes inhibits an early regulatory enzyme in he pathway

(3) The conversion of glucose to pyruvate is a multistep process requiring ten enzymes. If a mutation occurrs resulting in a lack of activity for one of these enzymes, which of the following happens?

a. the concentration of the metabolic intermediate which is the substrate of the missing enzyme is likely to increase and accumulate.

b. the cell will produce more of the other nine enzymes to maintain steady state.

c. the concentration of the metabolic intermediate which is the product of the missing enzyme will increase

d. pyruvate production will increase, leading to feedback regulation of the pathway

Answer 1

(1) When energy derived from ATP hydrolysis is coupled to an endergonic enzymatic reaction then

C. Hydrolysis of ATP provides the energy for the endergonic reaction at the active site where the substrate(s) are bound.

Explanation: Protein pumps that hydrolyze ATP can generate electrochemical gradients.With the help of specific enzymes, the cell can couple the energy of ATP hydrolysis directly to endergonic processes. In the free energy released from the hydrolysis of ATP is coupled to the energy-requiring active transport of the ion across a membrane.

(2) End product feedback inhibition of multistep pathways is a major mechanism for cellular regulation. In this proccess,

Explanation : the  end product causes an intermediate enzyme to form a different product and cause a branch in the pathway.When ATP allosterically inhibits an enzyme in an ATP generating pathway, the result is feedback inhibition, a mode of metabolic control. In feedback inhibition, a metabolic pathway is switched off by the inhibitory binding of its end product to an enzyme that acts early in the pathway. Therefore,

d. product of one of the last enzymes inhibits an early regulatory enzyme in the pathway

(3) The conversion of glucose to pyruvate is a multistep process requiring ten enzymes. If a mutation occurrs resulting in a lack of activity for one of these enzymes,

d. pyruvate production will increase, leading to feedback regulation of the pathway (as Glycolysis is the metabolic process of converting 1 molecule of glucose to 2 molecules of pyruvate through a series of 10 enzyme catalyzed reactions. )