a. glycolysis—preparatory reaction--cirtric acid cycle--electron transport system
Explanation:
Glycolysis is the first stage of cellular respiration that occurs in the cytoplasm of the cell. During glycolysis one 6 carbon glucose is converted into two molecules of 3 carbon pyruvic acid or pyruvate.
In the preparatory reaction, the pyruvate converted into a two-carbon molecule called acetyl CoA. In this reaction, a carbon dioxide molecule is released and a molecule of NADH is released.
The citric acid cycle begins with the reaction of the acetyl CoA with a four-carbon molecule in the mitochondrisl matrix. It goes through a cycle of reactions regenerating the four-carbon starting molecule. ATP, NADH and FADH₂ are produced.
The electron transport system is the terminal step of aerobic respiration that operates on the inner membrane of the mitochondria. Reduced coenzymes NADH and FADH₂ move along electron transport system release high-energy electrons and produce ATP.
