Question

the citric acid cycle is frequently described as the major pathway of aerobic catabolism, which means that it is an oxygen-dependent degradative process. however, none of the reactions of the cycle directly involves oxygen as a reactant. why is the pathway oxygen- dependent?

Answer 1

The Citric Acid Cycle is aerobic and oxygen-dependent because it produces NADH and FADH2 that require oxygen to accept electrons in the subsequent electron transport chain. Without oxygen, these carriers couldn't transfer electrons, which halts the cycle.

Step-by-step explanation:

The Citric Acid Cycle, also known as Krebs Cycle or TCA Cycle, is an essential part of cellular respiration that occurs in the mitochondrial matrix. Though the cycle itself doesn't use oxygen directly, it is aerobic because the reduced electron carriers NADH and FADH2 produced during the cycle must transfer their electrons to the electron transport chain, where oxygen acts as the final electron acceptor. Without oxygen, this electron transfer cannot occur, leading to an accumulation of NADH and FADH2 and a halt in the citric acid cycle. The cycle is mainly a series of redox reactions where high energy electrons are removed and subsequently used in oxidative phosphorylation to produce ATP. This means oxygen is indirectly necessary for the cycle to continue because it is needed in the subsequent electron transport chain to accept the electrons and allow the cycle to regenerate NAD+ and FAD, which are necessary for the continuation of the cycle.