Question 1

Which of the following statements best describes the role of the malate-aspartate shuttle in cellular metabolism?

Accepted Answer

It transfers reducing equivalents from cytosolic NADH into the mitochondrial matrix for use in the electron transport chain.

Question 2

A patient has a mutation that inactivates the enzyme isocitrate dehydrogenase in the TCA cycle. Which of the following would most likely accumulate as a result?

Accepted Answer

Isocitrate

Question 3

Which of the following best explains why the standard free energy change ($$\Delta G^\circ') of a $$reaction can differ from the actual free energy change ($$\Delta G) in a $$cell?

Accepted Answer

$$\Delta G^\circ' is $$measured at non-physiological concentrations, while $$\Delta G$$ accounts for actual cellular concentrations of reactants and products.

Question 4

Which of the following equations correctly relates the actual free energy change ($$\Delta G) to $$the standard free energy change ($$\Delta G^\circ'$$), the gas constant $$R$$, temperature $$T$$, and the reaction quotient $$Q$$?

Accepted Answer

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

Question 5

Which of the following best describes the difference between substrate-level phosphorylation and oxidative phosphorylation?

Accepted Answer

Substrate-level phosphorylation directly couples ATP synthesis to a chemical reaction, while oxidative phosphorylation uses a proton gradient generated by the electron transport chain.

Question 6

A defect in the carnitine shuttle would most directly impair which of the following processes?

Accepted Answer

Transport of fatty acyl-CoA into the mitochondrial matrix for beta-oxidation

Question 7

Which of the following is a key regulatory effect of malonyl-CoA in fatty acid metabolism?

Accepted Answer

It inhibits carnitine acyltransferase I, preventing fatty acid entry into mitochondria for beta-oxidation.

Question 8

During the light reactions of photosynthesis, what is the ultimate source of electrons for the electron transport chain in Photosystem II (PSII)?

Accepted Answer

Water ($$H_2O)$$

Question 9

Which of the following best describes the function of Rubisco in the Calvin Cycle?

Accepted Answer

It catalyzes the fixation of $$CO_2 to $$ribulose-1,5-bisphosphate, forming two molecules of 3-phosphoglycerate.

Question 10

Which of the following best explains why the glyoxylate cycle is important for plants and some microorganisms but not for animals?

Accepted Answer

It allows the net conversion of acetyl-CoA to glucose by bypassing the decarboxylation steps of the TCA cycle.

Question 11

A patient presents with a deficiency in Complex I of the electron transport chain. Which of the following would most likely be observed?

Accepted Answer

Decreased oxidation of NADH and reduced proton pumping across the inner mitochondrial membrane

Question 12

Which of the following best describes the role of F$$_0F$_1-$$ATPase (ATP synthase) in oxidative phosphorylation?

Accepted Answer

It uses the proton gradient across the inner mitochondrial membrane to drive the synthesis of ATP from ADP and inorganic phosphate.

Question 13

Which of the following statements about the regulation of the TCA cycle is correct?

Accepted Answer

High concentrations of ATP and NADH inhibit key enzymes of the TCA cycle.

Question 14

Which of the following best describes a transamination reaction in amino acid metabolism?

Accepted Answer

The transfer of an amino group from an amino acid to an alpha-keto acid, typically catalyzed by aminotransferases.

Question 15

Which of the following amino acids is classified as both ketogenic and glucogenic?

Accepted Answer

Isoleucine

Question 16

In the urea cycle, which of the following is the primary nitrogen donor for the synthesis of carbamoyl phosphate?

Accepted Answer

Ammonia ($$NH_3)$$

Question 17

Which of the following best explains why ketone bodies are produced during prolonged fasting?

Accepted Answer

Acetyl-CoA accumulates due to increased beta-oxidation of fatty acids and limited oxaloacetate for the TCA cycle.

Question 18

Which of the following best describes the function of the glucose-alanine cycle?

Accepted Answer

It transports amino groups from muscle to liver for urea synthesis while providing gluconeogenic substrate to the liver.

Question 19

Which of the following is a correct statement about the direction of a metabolic reaction based on the relationship between $$K ($$equilibrium constant) and $$Q ($$reaction quotient)?

Accepted Answer

If $$Q \u003c K$$, the reaction will proceed in the forward direction to reach equilibrium.

Comprehensive Study Notes: TCA Cycle, Electron Transport, Lipid Metabolism, Photosynthesis, and Nitrogen/Amino Acid Metabolism

Guida di studio - Domande di pratica

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