Which of the following sequences is correct for the downhill movement of electrons during cellular respiration? A. glucose – citric acid – ATP – NAD+ B. glucose – NADH – electron transport – O2 C. glucose – pyruvate – ATP - oxygen D. glucose – ATP – electron transport - NADH E. glucose – Kreb’s cycle – NADH - ATP

B. glucose – NADH – electron transport – O2

Explanation:

This is the sequence  from glycolysis in which  glucose molecules are split down to pyruvate, to oxidative phosphorylation.

During this process the electrons are released from glucose  molecule as it is oxidised multiple times as pyruvate, and other molecules formed subsequently in Kreb's cycle, until the oxidative phosphorylation is reached .

The makes the  carrier molecules to be reduced.Thus NAD→NADH,FAD→FADH .

The electrons from above are  transferred in hydrogen atoms  to matrix by these co-enzymes.Where the H is split to electrons  and protons.

The electrons for the ETC, produce the PMF for transporting  protons into the intramembrane space.

The concentration of protons generated the electrochemical gradients  which is needed to produce energy for for phosphorylation of ADP with Pi to form ATP by ATpase synthase.

The electrons moves as chain,and this is finally accepted by oxygen as the final electron acceptor.