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What Does ETC Accomplish in Mitochondria: Oxygen Electrons ATP Explained
Electron transport chain in cellular respiration shuttles electrons to oxygen while pumping protons to generate the gradient powering ATP synthase—not direct glucose ATP or synthesis—key mitochondrial function for biology exam prep.
Question
In the context of cellular respiration, what is the main function of the electron transport chain?
A. To transport electrons to oxygen and create a proton gradient
B. To create ATP directly from glucose
C. To break down ATP into ADP and phosphate
D. To synthesize glucose from pyruvate
Answer
A. To transport electrons to oxygen and create a proton gradient
Explanation
The electron transport chain (ETC), embedded in the inner mitochondrial membrane during cellular respiration, serves as the terminal stage of oxidative phosphorylation where high-energy electrons from NADH and FADH2 sequentially transfer through four protein complexes (I-IV) and mobile carriers like ubiquinone and cytochrome c, culminating in oxygen as the final acceptor to form water. This stepwise electron flow drives proton pumping from the mitochondrial matrix into the intermembrane space at complexes I, III, and IV, establishing an electrochemical proton gradient (proton-motive force) across the membrane that powers ATP synthase (complex V) via chemiosmosis to produce the bulk of ATP yield (~28-34 ATP per glucose). Unlike direct ATP production from glucose (glycolysis/Krebs cycle via substrate-level phosphorylation), ATP hydrolysis, or gluconeogenesis, the ETC maximizes energy extraction through redox reactions without consuming glucose or synthesizing it.