What is the significance of NADH and FADH2 in metabolism?

NADH and FADH2 play critical roles in metabolism, primarily as energy carriers. During the processes of glycolysis and the citric acid cycle, these molecules are generated as cells metabolize carbohydrates, fats, and proteins. Both NADH and FADH2 are electron carriers that store energy used to generate adenosine triphosphate (ATP), which is the primary energy currency of the cell.

In the mitochondrial electron transport chain, NADH and FADH2 donate electrons, leading to a series of reactions that ultimately culminate in the production of ATP through oxidative phosphorylation. This makes them indispensable for cellular energy production, enabling various biochemical processes that are essential for survival and proper functioning of the cells.

Understanding the role of NADH and FADH2 as energy carriers helps to highlight their importance in metabolic pathways, distinguishing them from waste products, neurotransmitter enhancers, or regulators of enzyme activity, as these functions do not capture their primary role in energy transfer and ATP generation.