During glycolysis, the electrons removed from glucose-derived intermediates are accepted by which cofactor?

Introduction / Context:
Glycolysis harvests energy by oxidizing glucose to pyruvate. Electrons captured during this process must be accepted by an oxidized cofactor to form a reduced carrier that later yields ATP via respiration or fermentation pathways.

Given Data / Assumptions:

• Focus on cytosolic glycolysis in most cells.
• Key oxidation step is catalyzed by glyceraldehyde-3-phosphate dehydrogenase.
• Standard cofactors NAD+/FAD are potential acceptors in metabolism.

Concept / Approach:
In glycolysis, glyceraldehyde-3-phosphate is oxidized and phosphorylated, and the electrons are transferred to NAD+ to form NADH. FAD is not used in the glycolytic pathway; it appears in later stages like the Krebs cycle (e.g., succinate dehydrogenase).

Step-by-Step Solution:
Identify the oxidation step: glyceraldehyde-3-phosphate → 1,3-bisphosphoglycerate.Note the cofactor: NAD+ accepts electrons and protons → NADH.Confirm no role for FAD, acetyl-CoA, or pyruvate as electron acceptors in glycolysis.Therefore, the correct cofactor is NAD+.

Verification / Alternative check:
Glycolytic stoichiometry shows a net production of 2 NADH per glucose, matching acceptance by NAD+.

Why Other Options Are Wrong:

• FAD: used in the Krebs cycle, not glycolysis.
• Acetyl-CoA/Pyruvate: metabolic intermediates, not primary electron acceptors in glycolysis.

Common Pitfalls:
Confusing glycolytic and mitochondrial dehydrogenases; always anchor cofactors to the specific pathway step.

Final Answer:
NAD+