Question 1

Which of the following best describes the relationship between photosynthesis and cellular respiration in the context of energy flow in ecosystems?

Accepted Answer

Photosynthesis uses light energy to produce organic molecules and O2, which are then used by cellular respiration to generate ATP, releasing CO2 and H2O.

Question 2

In the redox reaction $$\mathrm{C_6H_{12}O_6$ + 6 O_2$ ightarrow 6 CO_2$ + 6 H_2O + 	ext{Energy}}$$, which molecule is oxidized and which is reduced?

Accepted Answer

C6H12O6 is oxidized and O2 is reduced.

Question 3

What is the primary role of NAD+ in cellular respiration?

Accepted Answer

It functions as an electron carrier, accepting electrons and becoming reduced to NADH.

Question 4

During glycolysis, what is the net gain of ATP and NADH per molecule of glucose?

Accepted Answer

$$2$$ ATP and $$2$$ NADH

Question 5

Which of the following statements about substrate-level phosphorylation is correct?

Accepted Answer

It involves the direct transfer of a phosphate group from a substrate to ADP, forming ATP.

Question 6

What is the main function of the electron transport chain in mitochondria?

Accepted Answer

To transfer electrons from NADH and FADH2 to oxygen, creating a proton gradient used to drive ATP synthesis.

Question 7

Which of the following best explains why the exact number of ATP molecules produced from one molecule of glucose during cellular respiration is not known?

Accepted Answer

Phosphorylation and redox reactions are not directly coupled, ATP yield varies depending on electron carriers, and the proton-motive force is used for other work.

Question 8

In the absence of oxygen, which process allows glycolysis to continue by regenerating NAD+?

Accepted Answer

Fermentation

Question 9

Which of the following is a correct description of lactic acid fermentation?

Accepted Answer

Pyruvate is reduced directly by NADH to form lactate, with no release of CO2.

Question 10

A patient has a genetic defect that prevents the formation of the enzyme pyruvate dehydrogenase. Which of the following would most likely be observed in this patient’s cells?

Accepted Answer

Accumulation of pyruvate and decreased citric acid cycle activity.

Question 11

Which of the following is the correct sequence of events in aerobic cellular respiration?

Accepted Answer

Glycolysis → Pyruvate Oxidation → Citric Acid Cycle → Oxidative Phosphorylation

Question 12

Which molecule is the final electron acceptor in the electron transport chain of aerobic respiration?

Accepted Answer

O2

Question 13

A facultative anaerobe is placed in an environment with no oxygen but plenty of glucose. Which pathway will it primarily use to generate ATP?

Accepted Answer

Fermentation

Question 14

Which of the following best describes the role of oxygen in cellular respiration?

Accepted Answer

It is the final electron acceptor in the electron transport chain, forming water.

Question 15

Which of the following statements about the citric acid cycle is correct?

Accepted Answer

It generates 1 ATP, 3 NADH, and 1 FADH2 per turn.

Question 16

Which of the following is a real-life example of feedback inhibition in cellular respiration?

Accepted Answer

When ATP levels are high, enzymes in glycolysis are inhibited to slow down ATP production.

Question 17

Which of the following best explains why fats yield more ATP per gram than carbohydrates?

Accepted Answer

Fats have more hydrogen atoms and electrons, providing more high-energy electrons for the electron transport chain.

Question 18

A mutation prevents the formation of ubiquinone (Q) in the electron transport chain. What is the most likely consequence?

Accepted Answer

Electrons from NADH and FADH2 cannot be transferred to the next complexes, halting ATP production by oxidative phosphorylation.

Question 19

Which of the following is NOT a product of the complete aerobic breakdown of one molecule of glucose?

Accepted Answer

O2

Question 20

Which of the following best describes the evolutionary significance of glycolysis?

Accepted Answer

It is a widespread metabolic pathway that likely evolved early and is used by nearly all organisms.

Cellular Respiration and Fermentation: Mechanisms of Energy Production in Cells

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