Which of the following statements about cellular respiration is true?

Which of the following statements about cellular respiration is true?

• A. It occurs only in the presence of light
• B. It produces ATP through substrate-level phosphorylation
• C. It takes place exclusively in the mitochondria
• D. It is a process that requires no oxygen

Answer: (B)

The statement that cellular respiration produces ATP through substrate-level phosphorylation is true. During cellular respiration, there are several stages, including glycolysis, the Krebs cycle (also known as the citric acid cycle), and oxidative phosphorylation. In glycolysis, which occurs in the cytoplasm, glucose is broken down into pyruvate, and this process directly generates a small amount of ATP through substrate-level phosphorylation. Similarly, the Krebs cycle, occurring in the mitochondrial matrix, also produces ATP through substrate-level phosphorylation. This type of phosphorylation involves the direct transfer of a phosphate group to ADP to form ATP, as opposed to oxidative phosphorylation, which involves the electron transport chain and chemiosmosis. Understanding the processes of cellular respiration highlights the importance of ATP production in both aerobic and anaerobic conditions and emphasizes the role of substrate-level phosphorylation in generating energy. The other options do not accurately describe cellular respiration; it does not require light, it does not take place exclusively in the mitochondria (as glycolysis occurs in the cytoplasm), and while it can occur without oxygen in some organisms (anaerobic respiration), the statement implies that it requires no oxygen, which is not universally true.

The statement that cellular respiration produces ATP through substrate-level phosphorylation is true. During cellular respiration, there are several stages, including glycolysis, the Krebs cycle (also known as the citric acid cycle), and oxidative phosphorylation.

In glycolysis, which occurs in the cytoplasm, glucose is broken down into pyruvate, and this process directly generates a small amount of ATP through substrate-level phosphorylation. Similarly, the Krebs cycle, occurring in the mitochondrial matrix, also produces ATP through substrate-level phosphorylation. This type of phosphorylation involves the direct transfer of a phosphate group to ADP to form ATP, as opposed to oxidative phosphorylation, which involves the electron transport chain and chemiosmosis.

Understanding the processes of cellular respiration highlights the importance of ATP production in both aerobic and anaerobic conditions and emphasizes the role of substrate-level phosphorylation in generating energy. The other options do not accurately describe cellular respiration; it does not require light, it does not take place exclusively in the mitochondria (as glycolysis occurs in the cytoplasm), and while it can occur without oxygen in some organisms (anaerobic respiration), the statement implies that it requires no oxygen, which is not universally true.