Question 1

Which of the following statements best describes the difference between substrate-level phosphorylation and oxidative phosphorylation in cellular metabolism?

Accepted Answer

Substrate-level phosphorylation directly couples the transfer of a phosphate group to ADP using energy from a high-energy substrate, while oxidative phosphorylation uses the energy from a proton gradient generated by the electron transport chain to synthesize ATP.

Question 2

A patient has a mutation that impairs the function of Complex I in the electron transport chain. Which of the following would most likely be observed in this patient’s mitochondria?

Accepted Answer

Decreased proton gradient across the inner mitochondrial membrane and reduced ATP synthesis.

Question 3

Which of the following best explains why malonyl-CoA inhibits fatty acid oxidation in the mitochondria?

Accepted Answer

Malonyl-CoA inhibits the carnitine shuttle, preventing fatty acyl-CoA from entering the mitochondrial matrix for beta-oxidation.

Question 4

Which of the following equations correctly relates the standard free energy change ($$\Delta G^\circ'$$), the actual free energy change ($$\Delta G$$), the equilibrium constant ($$K$$), and the reaction quotient ($$Q) $$for a biochemical reaction?

Accepted Answer

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

Question 5

During the Calvin Cycle, which enzyme catalyzes the fixation of CO$$_2 to $$ribulose-1,5-bisphosphate, and what is the immediate product of this reaction?

Accepted Answer

Rubisco; two molecules of 3-phosphoglycerate

Question 6

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

Accepted Answer

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

Question 7

Which of the following statements about the glyoxylate cycle is correct?

Accepted Answer

It allows organisms like plants and bacteria to convert acetyl-CoA into glucose by bypassing the decarboxylation steps of the TCA cycle.

Question 8

A person is fasting and their liver is producing ketone bodies. Which of the following is a direct precursor for ketone body synthesis, and what are the three main ketone bodies produced?

Accepted Answer

Acetyl-CoA; acetoacetate, beta-hydroxybutyrate, and acetone

Question 9

Which of the following best describes the function of F$$_0F$_1-$$ATPase (ATP synthase) in mitochondria?

Accepted Answer

It synthesizes ATP from ADP and inorganic phosphate using the energy from the proton gradient across the inner mitochondrial membrane.

Question 10

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

Accepted Answer

Isoleucine

Question 11

Which of the following best explains why the energy charge of the cell (ATP/ADP ratio) regulates the TCA cycle?

Accepted Answer

High ATP inhibits key enzymes of the TCA cycle, while high ADP activates them, matching energy production to cellular demand.

Question 12

Which of the following is a correct description of the nitrogenase enzyme complex involved in nitrogen fixation?

Accepted Answer

It reduces atmospheric N$$_2 to NH$_3$$ using ATP and reduced ferredoxin as electron donors.

Question 13

Which of the following best describes the role of the carnitine shuttle in fatty acid metabolism?

Accepted Answer

It transports long-chain fatty acyl-CoA from the cytosol into the mitochondrial matrix for beta-oxidation.

Question 14

Which of the following statements about the organization of photosystems in the thylakoid membrane is correct?

Accepted Answer

Photosystem II is located in the stacked regions (grana), while Photosystem I is mainly in the unstacked regions (stroma lamellae) of the thylakoid membrane.

Question 15

Which of the following is the correct general reaction for transamination?

Accepted Answer

$$	ext{Amino acid}_1 + \alpha	ext{-ketoglutarate} ightarrow \alpha	ext{-keto acid}_1 + 	ext{glutamate}$$

Question 16

A defect in the urea cycle leads to the accumulation of ammonia in the blood. Which of the following is a key intermediate in the urea cycle that directly accepts the first nitrogen from ammonia?

Accepted Answer

Carbamoyl phosphate

Question 17

Which of the following best describes the difference between fatty acid synthesis and fatty acid degradation (beta-oxidation)?

Accepted Answer

Fatty acid synthesis occurs in the cytosol and uses NADPH, while beta-oxidation occurs in the mitochondrial matrix and uses NAD+ and FAD.

Question 18

Which of the following best explains why the glucose-alanine cycle is important during prolonged exercise or fasting?

Accepted Answer

It transports amino groups from muscle to liver as alanine, allowing safe removal of nitrogen and regeneration of glucose.

Question 19

Which of the following is the ultimate electron acceptor in non-cyclic electron flow during photosynthesis?

Accepted Answer

NADP$$^+$$

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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