AP BIOLOGY

Detailed explanation-1: -In eukaryotes, the Krebs cycle reactions take place in the mitochondrial matrix, a dense solution that surrounds the mitochondria crests: in addition to water, the matrix contains all the enzymes necessary for the biochemical reactions of the cycle, coenzymes, and phosphates.

Detailed explanation-2: -Within the mitochondrion, the citric acid cycle occurs in the mitochondrial matrix, and oxidative metabolism occurs at the internal folded mitochondrial membranes (cristae).

Detailed explanation-3: -Krebs’ cycle Enzymes within the mitochondria matrix are designed to oxidize the substrates within, in a cyclic manner. That is, every product of a reaction is a potential substrate for another reaction. The most reduced of the substrates (greatest available free energy) is citric acid (citrate).

Detailed explanation-4: -Fuel for the Krebs cycle comes from lipids (fats) and carbohydrates, which both produce the molecule acetyl coenzyme-A (acetyl-CoA). This acetyl-CoA reacts in the first step of the eight step sequence of reactions that comprise the Krebs cycle, all of which occur inside mitochondria of eukaryotic cells.