Question 1

Which of the following statements best describes the relationship between Gibbs free energy ($$\Delta G) $$and the equilibrium constant ($$K_{eq}) $$for a biochemical reaction at standard conditions?

Accepted Answer

$$\Delta G^\circ = -RT \ln K_{eq}$$

Question 2

A patient is diagnosed with a deficiency in glucose-6-phosphate dehydrogenase. Which metabolic pathway is most directly affected, and what is the primary consequence in red blood cells?

Accepted Answer

Pentose phosphate pathway; decreased NADPH production leading to increased oxidative stress

Question 3

Which enzyme catalyzes the first committed step of glycolysis and is highly regulated by allosteric effectors?

Accepted Answer

Phosphofructokinase-1 (PFK-1)

Question 4

During intense exercise, muscle cells rely on anaerobic glycolysis. What is the fate of pyruvate under these conditions, and which enzyme is responsible?

Accepted Answer

Pyruvate is converted to lactate by lactate dehydrogenase

Question 5

Which of the following best explains why hydrolysis reactions, such as ATP hydrolysis, are generally highly exergonic in cells?

Accepted Answer

Hydrolysis reactions increase entropy and release products that are stabilized by resonance and solvation

Question 6

A researcher adds labeled $$^{14}C-$$glucose (labeled at C-1) to a yeast extract under anaerobic conditions. After fermentation, where will the $$^{14}C $$label be found in the ethanol produced?

Accepted Answer

On the methyl carbon (C-2) of ethanol

Question 7

Which of the following is TRUE regarding the regulation of glycogen breakdown in muscle cells?

Accepted Answer

Glycogen phosphorylase is activated by phosphorylation in response to epinephrine

Question 8

Which of the following equations correctly relates the standard free energy change ($$\Delta G^\circ) to $$the actual free energy change ($$\Delta G) in a $$cell?

Accepted Answer

$$\Delta G = \Delta G^\circ + RT \ln Q$$

Question 9

Which of the following is a major function of NADPH produced by the oxidative branch of the pentose phosphate pathway?

Accepted Answer

Detoxification of reactive oxygen species in red blood cells

Question 10

In the Cori cycle, what is the primary role of the liver?

Accepted Answer

Convert lactate produced by muscles back into glucose via gluconeogenesis

Question 11

Which of the following statements about hexokinase IV (glucokinase) is CORRECT?

Accepted Answer

It is expressed primarily in the liver and has a higher $$K_m$$ for glucose than hexokinase I

Question 12

Which of the following is a direct consequence of a mutation that increases the activity of phosphofructokinase-1 (PFK-1) in liver cells?

Accepted Answer

Increased glycolytic flux and decreased gluconeogenesis

Question 13

Which of the following is the correct formula for calculating the standard free energy change ($$\Delta G^\circ') of a $$redox reaction using standard reduction potentials?

Accepted Answer

$$\Delta G^\circ' = -nF [E^\circ'_{acceptor} - E^\circ'_{donor}]$$

Question 14

Which of the following is a key regulatory difference between carbohydrate metabolism in liver and muscle tissue?

Accepted Answer

Liver can export glucose via gluconeogenesis, while muscle cannot

Question 15

Which of the following is the slowest method for regulating enzyme activity in metabolic pathways?

Accepted Answer

Increasing expression of a transcription factor that increases enzyme synthesis

Question 16

Which of the following is TRUE regarding the role of fructose-2,6-bisphosphate (F2,6BP) in the regulation of glycolysis and gluconeogenesis?

Accepted Answer

F2,6BP activates phosphofructokinase-1 and inhibits fructose-1,6-bisphosphatase

Question 17

Which of the following best describes the effect of ATP on phosphofructokinase-1 (PFK-1) activity?

Accepted Answer

ATP acts as both a substrate and an allosteric inhibitor of PFK-1

Question 18

Which of the following is a reason why the biosynthetic pathway for glucose (gluconeogenesis) is not simply the reverse of glycolysis?

Accepted Answer

Glycolysis contains irreversible steps that must be bypassed by different enzymes in gluconeogenesis

MCB 102: Metabolism Section F20 – Bioenergetics and Chemical Logic Study Notes

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