Question

The glycerol-3-phosphate shuttle can transport cytosolic NADH equivalents into the mitochondrial matrix (see Fig. 15.11c). In this shuttle, the protons and electrons are donated to FAD, which is reduced to FADH2. These protons and electrons are subsequently donated to coenzyme Q in the electron transport chain. Given that the number of ATP molecules made per NADH and FADH2 oxidation differ by ____? the amount of ATP generated per mole of glucose when the glycerol-3-phosphate shuttle would be ____ instead of 32.

Answer 1

The number of ATP molecules made per NADH and FADH2 oxidation differ by 1.

The amount of ATP generated per mole of glucose when the glycerol-3-phosphate shuttle would be 30 instead of 32.

Step-by-step explanation:

The glycerol-3-phosphate shuttle can transport cytosolic NADH equivalents into the mitochondrial matrix. In this shuttle, the protons and electrons are donated to FAD, which is reduced to FADH2. These protons and electrons are subsequently donated to coenzyme Q in the electron transport chain. Given that the number of ATP molecules made per NADH and FADH2 oxidation differ by 1, the amount of ATP generated per mole of glucose when the glycerol-3-phosphate shuttle would be 30 instead of 32.

FADH2 generates 1.5 ATP per molecule unlike NADH which generates 2.5 ATP per molecule. This is because electron transfer via FADH2 is not coupled to proton pumping unlike electron transfer reactions involving NADH. Thus, two moles of NADH from the oxidation of 2 moles of glyceraldehyde-2-phosophate to two moles of 1,3-bisphosphoglycerate will yield 3 moles of ATP rather than 5 moles when shuttled through the glycerol-3-phosphate shuttle. The glycerol-3-phosphate shuttle of cytosolic NADH shuttling occurs mainly in the brain and skeletal muscles and does not involve membrane transporters.