Which of the following is a distinction between cellular respiration and fermentation?
a. The transfer of from intermediate substrates to ADP
b. The movement of H+ across a membrane down its concentration gradient
c. The splitting of glucose into two molecules of pyruvate
d. Electrons moving through the electron transport chain

Verified step by step guidance

1. Step 1: Understand the key processes involved in cellular respiration and fermentation. Cellular respiration is an aerobic process (requires oxygen) that includes glycolysis, the citric acid cycle, and the electron transport chain. Fermentation, on the other hand, is an anaerobic process (does not require oxygen) and primarily involves glycolysis followed by the regeneration of NAD+ to allow glycolysis to continue.
2. Step 2: Analyze each option to determine if it applies to both cellular respiration and fermentation or only one of them. For example, consider whether the transfer of phosphate groups, movement of protons, splitting of glucose, or electron transport chain is unique to one process.
3. Step 3: Evaluate option (a): The transfer of phosphate groups from intermediate substrates to ADP (substrate-level phosphorylation) occurs in both cellular respiration and fermentation during glycolysis, so this is not a distinction.
4. Step 4: Evaluate option (b): The movement of H+ across a membrane down its concentration gradient is a feature of the electron transport chain in cellular respiration, but it does not occur in fermentation. This could be a distinction.
5. Step 5: Evaluate option (c) and (d): The splitting of glucose into two molecules of pyruvate (glycolysis) occurs in both processes, so it is not a distinction. Electrons moving through the electron transport chain is specific to cellular respiration and does not occur in fermentation, making it another possible distinction. Compare this with option (b) to determine the best answer.

Key Concepts

Cellular Respiration

Cellular respiration is a metabolic process that converts glucose and oxygen into energy (ATP), carbon dioxide, and water. It occurs in three main stages: glycolysis, the citric acid cycle, and oxidative phosphorylation. This process is highly efficient and involves the electron transport chain, where electrons are transferred through a series of proteins, ultimately producing ATP through chemiosmosis.

Fermentation

Fermentation is an anaerobic process that allows cells to generate energy without oxygen. It occurs after glycolysis when oxygen is not available, resulting in the conversion of pyruvate into lactic acid or ethanol and carbon dioxide. Fermentation produces less ATP compared to cellular respiration and does not involve the electron transport chain, making it a less efficient energy-producing pathway.

Electron Transport Chain

The electron transport chain (ETC) is a series of protein complexes located in the inner mitochondrial membrane that facilitate the transfer of electrons derived from NADH and FADH2. As electrons move through the chain, they release energy used to pump protons (H+) across the membrane, creating a proton gradient. This gradient drives ATP synthesis via ATP synthase, a key feature of aerobic cellular respiration, distinguishing it from fermentation.