AP BIOLOGY

CELL RESPIRATION

OXIDATIVE PHOSPHORYLATION

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
What does the NADH and/or FADH2 that is brought to the electron transport chain come from?
A
Glycolysis
B
Krebs cycle
C
Pyruvate oxidation
D
Cytoplasmic reactions
Explanation: 

Detailed explanation-1: -NADH and FADH2 made in the citric acid cycle (in the mitochondrial matrix) deposit their electrons into the electron transport chain at complexes I and II, respectively. This step regenerates NAD+ and FAD (the oxidized carriers) for use in the citric acid cycle.

Detailed explanation-2: -The Electron Transport Chain The ten NADH that enter the electron transport originate from each of the earlier processes of respiration: two from glycolysis, two from the transformation of pyruvate into acetyl-CoA, and six from the citric acid cycle. The two FADH2 originate in the citric acid cycle.

Detailed explanation-3: -NADH and FADH2 are both electron carriers that donate their electrons to the electron transport chain. The electrons ultimately reduce O2 to water in the final step of electron transport.

Detailed explanation-4: -During oxidative phosphorylation, electrons derived from NADH and FADH2 combine with O2, and the energy released from these oxidation/ reduction reactions is used to drive the synthesis of ATP from ADP.

Detailed explanation-5: -The electrons originally come from glucose. NADH and FADH2 carry electrons to the electron transport chain in cellular respiration. After electron transport in cellular respiration, the electrons are attracted to oxygen molecules (O2) which combine with protons (H+) to make water (H2O) molecules.

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