This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Glycolysis, Subject name: Biochemistry
Reducing equivalants produced in glycolysis are transported from cytosol to mitochondria by - 
Select and explain. 
A. Carnitine, B. Creatine, C. Malate shuttle, D. Glutamate shuttle
C: Malate shuttle
Answer: C: Malate shuttle 
Explanation: Ans. is 'c' i.e., Malate shuttle o Most of the NADH and FADH2, entering the mitochondrial electron transport chain arise from citric acid cycle and b-oxidation of fatty acids, located in the mitochondria itself.o However, NADH is also produced in the cytosol during glycolysis.o To get oxidized, NADH has to be transported into the mitochondria as respiratory chain (ETC) is located inside the mitochondria.o Since, the inner mitochondrial membrane is not permeable to cytoplasmic NADH, there are special shuttle systems which carry reducing equivalents from cytosolic NADH (rather than NADH itself) into the mitochondria by an indirect route.o Two such shuttle systems that can lead to transport of reducing equivalent from the cytoplasm into mitochondria are: -Malate shuttle (malate-aspartate shuttle system).Glycerophosphate shuttle.