Question

A. State the number of ATP molecules that are formed from the complete breakdown of one glucose molecule.

B. State how most of these ATP's are produced.

C. Describe the role of the NAD, FADH₂ and the ETS in ATP formation

Answer 1

The number of ATP molecules formed from glucose is the sum of the molecules produced in the 3 stages (plus the transition reaction): glycolysis, krebs cycle and the electron transport chain.

A) Glycolysis: This pathway takes 1 glucose and produces 2 ATP, 2 NADH and 2 pyruvate molecules

Transition reaction: This reaction takes 2 pyruvates and produces 2 CO2 and 2 acetyl coA molecules

Krebs cycle: This pathway takes 2 acetyl coA molecules to produce 2 ATP, 6 NADH and 2 FADH2 molecules

Electron transport chain: This pathway takes NADH and FADH2, it will produce 3 ATP per each NADH and 2 ATP per each FADH2. We already had 8 NADHs and 2 FADH2s, that is

(3)(8) = 24 ATP

(2)(2) = 4 ATP

Let's sum the total yield:

2 + 2 + 28 = 32 ATP molecules finally produced by one single glucose

B) As you could see, most of the ATP is produced by the electron transport chain, this pathway takes the energy from NADH and FADH2 to make an electrochemical gradient, the energy from this gradient is used to produce such quantities of ATP

C) NADH and FADH2 are known as the reductive power in the cell, they are capable of providing electrons, thus reducing another molecule. These molecules provide electrons to a a chain of different molecules that undergo redox reactions, the traveling electrons pump protons inside the mitochondrial matrix, this creates the electrochemical gradient that, finally, the ATP synthase will release by throwing protons down their gradient at the same time as it uses the energy to bind ADP with inorganic phosphate groups to create ATP