Which of the following mechanisms generates $\mathrm{ATP}$ using an electron transport chain?

• A. Oxidative phosphorylation
• B. Substrate-level phosphorylation
• C. Fermentation
• D. Photophosphorylation

Answer: (A)

Verified step by step guidance

1. Begin by understanding the concept of ATP generation. ATP, or adenosine triphosphate, is the energy currency of the cell, and its production is crucial for cellular processes.
2. Identify the mechanisms listed: Oxidative phosphorylation, Substrate-level phosphorylation, Fermentation, and Photophosphorylation. Each of these processes is involved in ATP production but operates differently.
3. Focus on oxidative phosphorylation. This process occurs in the mitochondria and involves the electron transport chain, where electrons are transferred through a series of complexes, ultimately leading to the production of ATP.
4. Understand the role of the electron transport chain in oxidative phosphorylation. Electrons are passed along the chain, and the energy released is used to pump protons across the mitochondrial membrane, creating a proton gradient.
5. Recognize that the proton gradient drives ATP synthesis via ATP synthase, a process known as chemiosmosis. This is the key feature of oxidative phosphorylation that distinguishes it from other ATP-generating mechanisms.