Which coenzyme is used in redox reactions during both glycolysis and the Krebs cycle?

NAD, or nicotinamide adenine dinucleotide, plays a crucial role in redox reactions during both glycolysis and the Krebs cycle. In these metabolic pathways, NAD serves as an electron carrier, facilitating the transfer of electrons during the oxidation of substrates.

During glycolysis, which occurs in the cytoplasm, NAD is reduced to NADH when it accepts electrons and protons (hydrogens) from glucose derivatives. This reduction is vital for the energy extraction from glucose, as it helps to drive the production of ATP.

In the Krebs cycle, which takes place in the mitochondrial matrix, NAD continues to function as an electron acceptor. Several steps of the Krebs cycle involve the oxidation of substrates, leading to the formation of NADH by capturing high-energy electrons released during these reactions. This NADH then feeds into the electron transport chain, ultimately contributing to ATP production.

The other coenzymes and molecules listed do have important functions in cellular metabolism, but they do not participate as directly as NAD does in both glycolysis and the Krebs cycle for the purpose of carrying electrons in redox reactions. Coenzyme A is primarily involved in the transport of acyl groups and does not participate directly in redox processes in these pathways. FAD (