Role Of Coenzymes

Question 1

What is Coenzyme A?

Answer 1

• Non organic molecule
• Nucleoside and a vitamin
• In link reaction, CoA binds to remainder of pyruvate molecule forming Acetyl CoA
• Supplies acetyl group to Kreb’s cycle (for respiration)

Question 2

What do NAD and FAD do? (generally)

Answer 2

• Accept hydrogens (become reduced)
• H atoms transferred from different stages of respiration to electron transport chain
• H atoms (H+ ions and electrons) removed, so coenzymes are oxidised

Question 3

What is the role of NAD and FAD in the synthesis of ATP?

Answer 3

• NADH and FADH2 donate electrons to electron transport chain
• NADH and FADH2 release H ions
• Electron transport chain releases energy via oxidation and reduction reactions, so H+ diffuses by active transport from inner mitochondrial membrane to intermembrane space
• H+ gradient created
• Movement of H+ down gradient by facilitated diffusion through ATP synthase gives energy required for ATP synthesis

Question 4

Which stages of respiration do reduced NAD and FAD come from?

Answer 4

NADH :
- 2 from glycolysis
- 2 from link reaction
- 6 from Kreb’s cycle

FADH2 :
- 2 from Kreb’s cycle