AP Biology Unit 3: Cellular Energetics

ATP synthase uses the energy of protons flowing down their electrochemical gradient across the inner mitochondrial membrane to synthesize ATP.

The stem asks students to explain a specific mechanism, not just recall a unit term: "During oxidative phosphorylation, what directly drives ATP synthase to produce ATP". The correct choice is supported by ATP synthase uses the energy of protons flowing down their electrochemical gradient across the inner mitochondrial membrane to synthesize ATP. The tempting alternatives such as Hydrolysis of DNA in the mitochondrial matrix or Direct attachment of oxygen to glucose in the cytosol fail because they do not produce the same outcome described in the stem.

Figure 1 must be used to determine which marker is supported by the visual model. Marker C: The Calvin cycle uses ATP and NADPH to help fix carbon dioxide into carbohydrate intermediates. The Calvin cycle occurs in the stroma and uses ATP and NADPH from the light reactions to fix carbon dioxide into organic molecules.

The evidence in the prompt matters before the topic label: "A diagram shows ATP and NADPH entering a cycle in the chloroplast stroma, while carbon dioxide is incorporated...". The supported answer is "Calvin cycle" because The Calvin cycle occurs in the stroma and uses ATP and NADPH from the light reactions to fix carbon dioxide into organic molecules. Distractors such as Glycolysis or Translation either ignore the stated pattern or name a related concept without matching the evidence.

ATP hydrolysis is exergonic and can be coupled to endergonic cellular processes such as active transport.

The stem asks students to explain a specific mechanism, not just recall a unit term: "A cell uses energy from ATP hydrolysis to move ions against their concentration gradients. Which statement best...". The correct choice is supported by ATP hydrolysis is exergonic and can be coupled to endergonic cellular processes such as active transport. The tempting alternatives such as It stores all cellular energy permanently in phosphate bonds or enzyme is consumed during the reaction, so product formation... fail because they do not produce the same outcome described in the stem.