NADH functions as a crucial electron carrier in the process of cellular respiration, enabling the transfer of energy within cells.

Cellular respiration is essential for all living organisms, as it is the primary mechanism by which cells extract energy from nutrients. This energy is stored in the form of adenosine triphosphate (ATP), which fuels various cellular activities.

The process of cellular respiration is divided into several stages: glycolysis, the Krebs cycle, and the electron transport chain. NADH plays a significant role in both glycolysis and the Krebs cycle. During glycolysis, glucose is converted into two molecules of pyruvate, resulting in the production of a small amount of ATP and the reduction of NAD^+ to NADH. In the subsequent Krebs cycle, the pyruvate undergoes further breakdown, leading to the production of additional NADH.

The NADH molecules generated in these stages then proceed to the electron transport chain, the final stage of cellular respiration. In this stage, NADH donates its electrons to the first protein complex in the chain. This donation initiates a series of redox reactions, where electrons are transferred between molecules. These reactions create a proton gradient across the mitochondrial membrane. The energy stored in this gradient is subsequently utilized to synthesize ATP from ADP and inorganic phosphate.

In summary, NADH acts as a carrier, transporting high-energy electrons derived from glucose and other nutrients to the electron transport chain, where their energy is harnessed to generate ATP. The absence of NADH would impede the transfer of energy within cells, highlighting its vital role in cellular respiration.