Energy currency: The complete oxidation of glucose ultimately provides usable cellular energy predominantly in the form of which molecule?

Introduction / Context:Cells convert nutrient energy into a universally useful form. While multiple reduced cofactors are produced during catabolism, the immediate “spendable” currency for biological work is ATP.

Given Data / Assumptions:

• Glucose oxidation yields NADH and FADH2.
• Oxidative phosphorylation converts redox energy into ATP via ATP synthase.
• ATP powers transport, biosynthesis, and mechanical work.

Concept / Approach:Although NADH and FADH2 carry high-energy electrons, their energy is realized as ATP through the electron transport chain and chemiosmotic phosphorylation. Coenzyme A and pyruvate are intermediates, not energy currency.

Step-by-Step Solution:Glycolysis and Krebs cycle produce ATP directly (substrate-level) and NADH/FADH2.ETC uses NADH/FADH2 to pump protons, storing energy in a gradient.ATP synthase uses this gradient to form ATP from ADP + Pi.Therefore, the usable end product is ATP.

Verification / Alternative check:Cellular processes universally utilize ATP hydrolysis (ATP → ADP + Pi) to drive endergonic reactions.

Why Other Options Are Wrong:

• FADH2: carrier, not the principal energy currency.
• Coenzyme A/Pyruvate: metabolic intermediates.

Common Pitfalls:Equating high-energy electron carriers with direct energy spend; cells must convert their energy into ATP to perform most work.

Final Answer:ATP