Which processes occur in aerobic metabolism to produce ATP from glucose and fatty acids?

• A. Glycolysis, Krebs cycle, and electron transport chain
• B. Fermentation only
• C. Glycolysis only
• D. Beta-oxidation only

Answer: (A)

In aerobic metabolism, ATP is produced mainly through a sequence of stages that feed into oxidative phosphorylation. Glucose is first broken down by glycolysis in the cytoplasm to form pyruvate, which is then converted to acetyl-CoA and enters the Krebs cycle in the mitochondria. The Krebs cycle generates NADH and FADH2, which donate electrons to the electron transport chain, and the flow of electrons drives ATP production. Fatty acids are first broken down by beta-oxidation in the mitochondria to acetyl-CoA, which also enters the Krebs cycle and then feeds the electron transport chain to produce more ATP. This combination—glycolysis, the Krebs cycle, and the electron transport chain—covers how ATP is produced from glucose and from fatty acids under aerobic conditions.

Fermentation is anaerobic and does not involve the Krebs cycle or the electron transport chain, and beta-oxidation by itself doesn’t account for the full aerobic ATP yield since it’s the acetyl-CoA from beta-oxidation that feeds the Krebs cycle and downstream oxidative phosphorylation.