What is the role of NADH and FADH2 in cellular respiration?

NADH and FADH2 play crucial roles in cellular respiration, primarily as electron carriers. During the processes of glycolysis and the citric acid cycle (also known as the Krebs cycle), glucose is broken down, and high-energy electrons are transferred to these coenzymes.

NAD+ is reduced to form NADH, while FAD is reduced to FADH2. Both NADH and FADH2 then transport these high-energy electrons to the electron transport chain, a series of protein complexes located in the inner mitochondrial membrane. As the electrons move through the chain, their energy is used to pump protons across the mitochondrial membrane, creating an electrochemical gradient. This gradient drives the synthesis of ATP when protons flow back across the membrane through ATP synthase.

While NADH and FADH2 do contribute to the production of ATP through this process by enabling oxidative phosphorylation, they do not directly produce ATP. Instead, their primary function is to carry and donate electrons, allowing for the conversion of the energy stored in glucose to a usable form, which is ATP, later in the respiration process. This distinction is important for understanding the layered complexity of cellular respiration and the different roles various molecules play.

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