Question

What are the three different metabolic pathways that are responsible for the production of ATP?

a) substrate inhibition, catabolism, and fermentation
b) glycolysis, the reactions on the electron transport chain, and the Krebs (citric acid) cycle
c) hydrolysis, active transport, and the light reactions
d) glycolysis, oxidation, and the Calvin cycle reactions
e) None of the above is correct."

Answer 1

The three metabolic pathways responsible for ATP production are glycolysis, the Krebs cycle, and oxidative phosphorylation via the electron transport chain. Glycolysis and the Krebs cycle generate a small amount of ATP directly, while the majority comes from oxidative phosphorylation, driven by a proton gradient enabling the synthesis of ATP.

Step-by-step explanation:

Metabolic Pathways for ATP Production

The three different metabolic pathways responsible for the production of ATP are glycolysis, the Krebs (citric acid) cycle, and the reactions on the electron transport chain. During glycolysis, glucose is converted into pyruvate, yielding a small amount of ATP through substrate-level phosphorylation. The pyruvate produced enters the Krebs cycle, which generates a small amount of ATP directly and a larger amount indirectly through the production of NADH and FADH2. These electron carriers donate electrons to the electron transport chain, which functions in conjunction with chemiosmosis in the process of oxidative phosphorylation, the primary source of ATP in aerobic organisms. Here, a proton gradient generates the energy needed to synthesize ATP from ADP, with oxygen serving as the final electron acceptor to ultimately form water.

If oxygen is not present, cells can produce ATP through fermentation, which allows glycolysis to continue by regenerating NAD+. However, fermentation alone yields no additional ATP beyond what is produced during glycolysis.