Question

What is the role of FADH2 and NADH in cellular respiration?
(A) Catalyze the breakdown of glucose to three carbon sugars
(B) Carry electrons to the Cytochrome membrane proteins
(C) Catalyzes the addition of a phosphate group to ADP
(D) Act as a final electron acceptor in the electron transport chain
(E) Transport hydrogen ions across the inner mitochondrial membrane

Answer 1

Hint: FADH2 and NADH are formed from FAD and NAD+ through reduction-oxidation reactions during cellular respiration. And it has a great role during the completion of the reactions.

Complete answer: The FADH2 stands for Flavin adenine dinucleotide, is the redox cofactor and formed during the last reactions of electron transport chain process and NADH stands for nicotinamide adenine dinucleotide, is similar as FADH2 and it also formed in electron transport chain reactions.
During the respiration process six molecules of NADH and two molecules of FADH2 is produced. During the respiration cycle a small amount of energy is formed in the form of ATP through which these two molecules are produced by reduction and oxidation of FAD and NAD+.
These two compounds are used in the movement of electrons in the electron transport chain in the final respiration stage where most of the energy is lost and created from mitochondria.

Now lets us find the solution from the given options:
1. Catalyze the breakdown of glucose to three carbon sugars; this function is carried out by the enzymes to form energy in the form of ATP.
2. Carry electrons to the Cytochrome membrane proteins; this function is carried out by the complex integral membrane proteins called Cytochrome C.
3. Catalyzes the addition of a phosphate group to ADP; this function is carried out by an enzyme termed as kinase that adds phosphate group to other molecules including ADP.
4. Act as a final electron acceptor in the electron transport chain; this function involves FADH2 and NADH molecules, it provides energy during the last part of the electron transport chain.
5. Transport hydrogen ions across the inner mitochondrial membrane; this function is carried out with the help of a membrane protein called ATP synthase to form hydrogen ions.

Hence, the correct option is (D). Act as a final electron acceptor in the electron transport chain.

Note: In the cellular respiration process, that is electron transport chain protons are pumped to the intermembrane space from the mitochondrial matrix and oxygen is reduced to form water molecules.