This is a question about \"substrate level phosphorylation\" -- that is, reactio

Question

This is a question about "substrate level phosphorylation" -- that is, reactions in which ATP is synthesized using energy released from the (implicit) hydrolysis of another high energy compound. (Such phosphorylation stands in contrast to the phosphorylation of ADP in oxidative phosphorylation.)

Which of these reactions is NOT an example of substrate-level phosphorylation?

A. Reaction 7 of glycolysis

B. Reaction 10 of glycolysis

C. Reaction 5 of the citric acid cycle

D. ATP synthesis by ATP synthase

Glycogen phosphorylase releases phosphorylated glucose units from glycogen.

Which of the following is a TRUE statement?

A. The net yield of ATP, in glycolysis, from a phosphorylated glucose unit +3.

B. The compound released from glycogen by glycogen phosphorylase is glucose-6-phosphate.

C. Glycogen phosphorylase exists only in liver.

D. Glycogen breakdown is not affected by glucagon or by ephinephrine.

Your text describes three stages in fatty acid catabolism. The second of these is "activation" -- the synthesis of acylCoA (or fatty-acylCoA) molecules from HSCoA and free fatty acids. What is TRUE about fatty acid activation?

A. PPi released from ATP in synthesis of an acyl-CoA is hydrolyzed to 2 Pi, to make the acylCoA synthesis irreversible.

B. AcylCoA synthesis does not require the expenditure of energy (in the form of ATP hydrolysis, for instance)

C. A fatty acid is joined to HSCoA in a phosphoanhydride linkage.

D. This step (activation) is optional in fatty acid catabolism; it's not strictly necesarry for breakdown of a fatty acid.

Explanation / Answer

1) ATP synthesis by ATP synthase is not an example of substrate-level phosphorylation

Thus, the correct option is D

2) Glycogen phosphorylase exists only in liver. Thus, the correct option is C

3) PPi released from ATP in synthesis of an acyl-CoA is hydrolyzed to 2 Pi, to make the acylCoA synthesis irreversible. Thus, the correct option is A

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