Which statement about the glycerol phosphate shuttle is true?

Which statement about the glycerol phosphate shuttle is true?

• A. It yields more ATP than the malate-aspartate shuttle.
• B. It produces less overall energy than the malate-aspartate shuttle.
• C. It does not involve Coenzyme Q.
• D. It transfers electrons to Complex II.

Answer: (B)

The key idea here is how the shuttle that takes electrons from cytosolic NADH into the mitochondria sets the final amount of ATP you generate. The glycerol phosphate shuttle transfers those electrons to Coenzyme Q via a flavin adenine dinucleotide (FAD) step in the inner membrane. That means the electrons enter the electron transport chain at Coenzyme Q, effectively bypassing Complex I. Because NADH-derived electrons entering at Complex I typically drive more proton pumping than those entering at CoQ, the glycerol phosphate shuttle yields less ATP—about 1.5 ATP per cytosolic NADH—compared with the malate–aspartate shuttle, which delivers NADH into the matrix and feeds Complex I, yielding about 2.5 ATP per cytosolic NADH. So this shuttle produces less energy than the malate–aspartate shuttle. It does involve Coenzyme Q, and electrons aren’t transferred directly to Complex II, so those statements aren’t true.

The key idea here is how the shuttle that takes electrons from cytosolic NADH into the mitochondria sets the final amount of ATP you generate. The glycerol phosphate shuttle transfers those electrons to Coenzyme Q via a flavin adenine dinucleotide (FAD) step in the inner membrane. That means the electrons enter the electron transport chain at Coenzyme Q, effectively bypassing Complex I. Because NADH-derived electrons entering at Complex I typically drive more proton pumping than those entering at CoQ, the glycerol phosphate shuttle yields less ATP—about 1.5 ATP per cytosolic NADH—compared with the malate–aspartate shuttle, which delivers NADH into the matrix and feeds Complex I, yielding about 2.5 ATP per cytosolic NADH. So this shuttle produces less energy than the malate–aspartate shuttle. It does involve Coenzyme Q, and electrons aren’t transferred directly to Complex II, so those statements aren’t true.