Question 1

Which of the following best explains why ATP is considered the 'energy currency' of the cell?

Accepted Answer

ATP contains high-energy phosphate bonds that, when hydrolyzed, release energy that can be used to drive endergonic cellular processes.

Question 2

During glycolysis, which enzyme catalyzes the irreversible phosphorylation of glucose to glucose-6-phosphate, and what class of enzyme does it belong to?

Accepted Answer

Hexokinase; transferase

Question 3

Which of the following statements best describes substrate-level phosphorylation?

Accepted Answer

It is the direct transfer of a phosphate group from a phosphorylated intermediate to ADP, forming ATP.

Question 4

Which of the following best explains why the stepwise oxidation of glucose in cells is advantageous compared to direct combustion?

Accepted Answer

Stepwise oxidation allows for controlled release and capture of energy in the form of ATP and NADH, minimizing energy loss as heat.

Question 5

Which of the following is the correct net equation for glycolysis?

Accepted Answer

$$\mathrm{Glucose} + 2\ \mathrm{NAD}^+ + 2\ \mathrm{ADP} + 2\ \mathrm{P_i} \rightarrow 2\ \mathrm{Pyruvate} + 2\ \mathrm{NADH} + 2\ \mathrm{ATP} + 2\ \mathrm{H_2O} + 2\ \mathrm{H}^+$$

Question 6

A patient with a deficiency in lactate dehydrogenase would most likely experience which of the following metabolic consequences during intense exercise?

Accepted Answer

Impaired regeneration of NAD$$^+$$, leading to decreased glycolytic flux and reduced ATP production under anaerobic conditions.

Question 7

Which of the following statements correctly compares glycolysis and gluconeogenesis?

Accepted Answer

Glycolysis is a catabolic pathway that breaks down glucose to pyruvate, while gluconeogenesis is an anabolic pathway that synthesizes glucose from non-carbohydrate precursors.

Question 8

Which enzyme is responsible for the key regulatory step in glycolysis, and how is it regulated by fructose-2,6-bisphosphate?

Accepted Answer

Phosphofructokinase-1 (PFK-1); activated by fructose-2,6-bisphosphate

Question 9

During aerobic respiration, why does the reoxidation of 1 NADH generate more ATP than the reoxidation of 1 FADH$$_2$$?

Accepted Answer

NADH donates electrons to Complex I of the electron transport chain, resulting in more protons pumped across the inner mitochondrial membrane compared to FADH$$_2$$, which donates electrons to Complex II.

Question 10

Which of the following best describes the role of the chemiosmotic coupling mechanism in oxidative phosphorylation?

Accepted Answer

It uses the energy stored in a proton gradient across the inner mitochondrial membrane to drive ATP synthesis via ATP synthase.

Question 11

A cell is exposed to an uncoupling agent such as 2,4-dinitrophenol (DNP). What is the most likely immediate effect on mitochondrial ATP production and oxygen consumption?

Accepted Answer

ATP production decreases while oxygen consumption increases.

Question 12

Which of the following correctly summarizes the net products (per glucose molecule) of the citric acid cycle?

Accepted Answer

$$2\ \mathrm{ATP},\ 6\ \mathrm{NADH},\ 2\ \mathrm{$$FADH_2$$},\ 4\ \mathrm{CO_2$}$$

Question 13

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

Accepted Answer

The Calvin cycle uses ATP and NADPH to fix CO$$_2$$ and synthesize triose phosphates.

Question 14

Which of the following best distinguishes between cyclic and noncyclic photophosphorylation in photosynthesis?

Accepted Answer

Cyclic photophosphorylation involves only Photosystem I and produces ATP but not NADPH or O$$_2$$; noncyclic photophosphorylation involves both Photosystem I and II and produces ATP, NADPH, and O$$_2.$$

Question 15

A plant exposed to high oxygen concentrations during the day will experience increased rates of which process, and what is the main enzyme involved?

Accepted Answer

Photorespiration; RUBISCO

Question 16

Which of the following statements best explains why C4 plants are more efficient than C3 plants under hot, dry conditions?

Accepted Answer

C4 plants spatially separate CO$$_2$$ fixation and the Calvin cycle, reducing photorespiration by concentrating CO$$_2$$ around RUBISCO.

Question 17

In the Cori cycle, what is the fate of lactate produced in muscle cells during anaerobic exercise?

Accepted Answer

It is transported to the liver, where it is converted back to glucose via gluconeogenesis.

Question 18

Which of the following best describes the role of dehydrogenases in cellular metabolism?

Accepted Answer

They catalyze the removal of hydrogen atoms from substrates, transferring electrons to coenzymes such as NAD$$^+ or $$FAD.

Question 19

A patient with a genetic defect in the electron shuttle system that transfers cytosolic NADH into the mitochondria would most likely have which of the following consequences?

Accepted Answer

A lower maximum ATP yield per glucose molecule, because cytosolic NADH cannot contribute fully to oxidative phosphorylation.

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