Multiple Choice (1) When energ
Multiple Choice
(1) When energy derived from ATP hydrolysis is coupled to anendergonic enzymatic reaction, which of the following is the mostlikely mechanistic description of this coupling?
a. ATP binds at a regulatory site and puts the enzyme in a moreactive conformation.
b. ATP binds at one active site of the enzyme and thesubstrate(s) bind at another.
c. Hydrolysis of ATP provides the energy for the endergonicreaction at the active site where the substrate(s) are bound.
d. ATP and substrate compete for binding to the same activesite.
(2) End product feedback inhibition of multistep pathways is amajor mechanism for cellular regulation. In this proccess, the
a. product of the last enzyme inhibits the substrate of the lastenzyme.
b. product of an early metabolically irreversible enzymeinhibits the last enzyme in the pathway.
c. An early regulatory enzyme in the pathway is inhibited whenATP concentrations are depleted.
d. product of one of the last enzymes inhibits an earlyregulatory enzyme in he pathway
(3) The conversion of glucose to pyruvate is a multistep processrequiring ten enzymes. If a mutation occurrs resulting in a lack ofactivity for one of these enzymes, which of the followinghappens?
a. the concentration of the metabolic intermediate which is thesubstrate of the missing enzyme is likely to increase andaccumulate.
b. the cell will produce more of the other nine enzymes tomaintain steady state.
c. the concentration of the metabolic intermediate which is theproduct of the missing enzyme will increase
d. pyruvate production will increase, leading to feedbackregulation of the pathway
Answer:
(1) When energy derived from ATP hydrolysis is coupledto an endergonic enzymatic reaction then
C. Hydrolysis of ATP provides the energy for theendergonic reaction at the active site where the substrate(s) arebound.
Explanation: Protein pumps thathydrolyze ATP can generate electrochemicalgradients.With the help of specific enzymes, thecell can couple the energy of ATP hydrolysis directly to endergonicprocesses. In the free energy released from thehydrolysis of ATP is coupled to the energy-requiring activetransport of the ion across a membrane.
(2) End product feedback inhibition of multisteppathways is a major mechanism for cellular regulation. In thisproccess,
Explanation :the end product causes an intermediate enzyme to form adifferent product and cause a branch in the pathway.When ATPallosterically inhibits an enzyme in an ATP generating pathway, theresult is feedback inhibition, a mode of metabolic control. Infeedback inhibition, a metabolic pathway is switched off by theinhibitory binding of its end product to an enzyme that acts earlyin the pathway. Therefore,
d. product of one of the last enzymes inhibits an earlyregulatory enzyme in the pathway
(3) The conversion of glucose to pyruvate is a multistepprocess requiring ten enzymes. If a mutation occurrs resulting in alack of activity for one of these enzymes,
d. pyruvate production will increase, leading tofeedback regulation of the pathway (as Glycolysis is the metabolicprocess of converting 1 molecule of glucose to 2 molecules ofpyruvate through a series of 10 enzyme catalyzed reactions.)
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