Question

Where do NADH and FADH₂ get the electrons that they bring to the electron transport chain?

Answer 1

NADH and FADH2 gets electrons in various steps of cellular respiration, these are :-
1. Glycolysis - In this step total 2 NAD+ gets electrons and get converted into 2 NADH per glucose.
Step is - Conversion of glyceraldehyde-3 phosphate to 1,3- bisphosphoglycerate.

2. Pyruvate decarboxylation - In this step one NAD+ per pyruvate gets electrons and converted to NADH.
• Pyruvate dehydrogenase complex helps in this step.

3. Krebs cycle - In this cycle, total 3 NAD+ and 1 FADH get electrons and get converted to NADH and FADH2.
Steps are -
(a) for NADH -
• Conversion of isocitrate to alpha ketogluterate and then in succinyl coA.
• Conversion of malate to oxaloacetate.
(b) for FADH2 -
• Conversion of succinate to fumarate.

Now NADH and FADH2 transfer these electrons to electron transport chain and make large amount of ATP.