Question

unit 3 preteset
3.1.8 - 12.0 which of the following best explains why aerobic respiration is more energy efficient than anaerobic respiration?
○ aerobic respiration occurs in one step, while anaerobic respiration requires several steps.
○ aerobic respiration fully breaks down glucose, while anaerobic respiration does not.
○ aerobic respiration produces less carbon dioxide per molecule of glucose.
○ aerobic respiration produces more atp per molecule of glucose.

Explanation:

Aerobic respiration produces more ATP (adenosine triphosphate) per molecule of glucose. ATP is the energy - carrying molecule in cells. In aerobic respiration, glucose is completely oxidized in the presence of oxygen, and through glycolysis, the Krebs cycle, and the electron transport chain, a large amount of ATP (about 36 - 38 ATP molecules per glucose molecule) is generated. In anaerobic respiration (such as fermentation), glucose is only partially broken down, and much less ATP is produced (2 ATP molecules per glucose molecule in alcoholic or lactic acid fermentation).

• Option 1: Aerobic respiration has multiple steps (glycolysis, Krebs cycle, electron transport chain), while anaerobic respiration (e.g., fermentation) has fewer steps. So this option is incorrect.
• Option 2: While it is true that aerobic respiration fully breaks down glucose and anaerobic respiration does not (in the sense of not using the full set of oxidative steps), the key measure of energy efficiency is ATP production.
• Option 3: Aerobic respiration actually produces more carbon dioxide per molecule of glucose (6 molecules of \(CO_2\) for aerobic respiration of one glucose molecule, and in alcoholic fermentation, 2 molecules of \(CO_2\) per glucose molecule). So this option is incorrect.

Answer:

Aerobic respiration produces more ATP per molecule of glucose.