NADH

Definition

NADH, or nicotinamide adenine dinucleotide (reduced form), is a coenzyme that plays a crucial role in cellular metabolism by serving as an electron carrier in various metabolic pathways. It is primarily involved in redox reactions, where it helps transfer electrons from one molecule to another, thus facilitating energy production through processes like cellular respiration. The generation of NADH occurs during glycolysis, the Krebs cycle, and the beta-oxidation of fatty acids, highlighting its importance in cellular energetics and metabolic pathways.

5 Must Know Facts For Your Next Test

1. NADH is produced during glycolysis, where one glucose molecule is broken down into two molecules of pyruvate.
2. During the Krebs cycle, each acetyl-CoA that enters produces three NADH molecules, significantly contributing to the cell's total NADH pool.
3. NADH carries high-energy electrons to the electron transport chain, where it helps generate ATP through oxidative phosphorylation.
4. The conversion of NAD+ to NADH is a reversible reaction, allowing for a continuous cycle of electron transfer within metabolic pathways.
5. NADH not only plays a vital role in energy production but also contributes to various biosynthetic processes by providing reducing power.

Review Questions

• How does NADH function as an electron carrier in metabolic pathways, and why is this role important for cellular energetics?
  • NADH functions as an electron carrier by accepting electrons during redox reactions and transporting them to various metabolic pathways, primarily the electron transport chain. This role is essential for cellular energetics because it allows for the efficient production of ATP through oxidative phosphorylation. By facilitating the transfer of electrons, NADH helps drive the reactions necessary for energy release from nutrients, enabling cells to meet their energy demands.
• Describe the process by which NADH is generated during glycolysis and the Krebs cycle, and discuss its significance in metabolism.
  • During glycolysis, glucose is broken down into pyruvate, generating two molecules of NADH in the process. In the Krebs cycle, each acetyl-CoA produces three NADH molecules per cycle. The significance of NADH in metabolism lies in its role as a high-energy electron carrier; it captures and transports energy from substrates to the electron transport chain, where it ultimately contributes to ATP synthesis. This efficient energy transfer is crucial for maintaining cellular functions.
• Evaluate the impact of NADH on ATP production during oxidative phosphorylation and how this process reflects the interconnectedness of metabolic pathways.
  • NADH has a direct impact on ATP production during oxidative phosphorylation by donating its electrons to the electron transport chain. As electrons move through this chain, they create a proton gradient across the mitochondrial membrane that drives ATP synthase to produce ATP. This process illustrates the interconnectedness of metabolic pathways; for example, NADH generated from glycolysis and the Krebs cycle feeds into oxidative phosphorylation, linking catabolic processes that break down nutrients with ATP synthesis, which powers anabolic processes needed for cell growth and function.

Related terms

NAD+: NAD+ (nicotinamide adenine dinucleotide) is the oxidized form of NADH and acts as an electron acceptor in redox reactions.

ATP: Adenosine triphosphate (ATP) is the primary energy carrier in cells, produced during cellular respiration and used to fuel various cellular processes.

Oxidative phosphorylation: A process that occurs in the mitochondria, where NADH donates electrons to the electron transport chain, ultimately leading to ATP production.