NADH produced in glycolysis is often called \"cytoplasmic NADH\" (or, \"cytosoli
ID: 49453 • Letter: N
Question
NADH produced in glycolysis is often called "cytoplasmic NADH" (or, "cytosolic NADH"). It has to get into mitochondria to be oxidized in oxphos. But there is a problem: the inner mitochondrial membrane is impermeable to NADH.
Which of the following is true about the mechansm(s) by which cytosolic NADH provides electrons (in the form of NADH or QH2) for entry into oxphos?
A. NADH is directly transported in some organs across the inner mitochondrail membrane, by facilitated diffusion.
B. NADH is taken up directly, at the expense of 1 ATP per NADH, into the mitochondrial matrix by active transport.
C. Malate (formed by reduction of oxaloacetate by NADH) moves across the inner mitochondrial membrane, into the matrix, where oxidation of malate to oxaloacetate produces NADH, which enters electron transport.
D. Cytosolic NADH cannot contribute, directly or indirectly, to electron transport.
Explanation / Answer
In the glycolytic pathway the inner mitochondria is immpermeable to the NADH and NAD+. So they cannot enter the inner mitochondria easily. It has to be facilitated by some medium. This can be facilitated by malate shuttle also called the malate-aspartate mechanism.
Malate moves across the inner mitochondrial membrane int the matrix where oxidation of malate to oxaloacetate by malate dehydrogenase produces NADH.
HEnce the correct option is c.
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