NADH

Definition

NADH, or nicotinamide adenine dinucleotide (reduced form), is a crucial coenzyme in cellular metabolism that acts as an electron carrier in redox reactions. It plays a significant role in energy production by facilitating the transfer of electrons during metabolic pathways such as glycolysis and the citric acid cycle, ultimately contributing to ATP synthesis through oxidative phosphorylation.

5 Must Know Facts For Your Next Test

1. NADH is generated during glycolysis, the citric acid cycle, and the conversion of pyruvate to acetyl-CoA, capturing high-energy electrons.
2. In the electron transport chain, NADH donates electrons to Complex I, initiating a series of redox reactions that ultimately lead to ATP production.
3. Each molecule of NADH can generate approximately 2.5 molecules of ATP when fully oxidized through oxidative phosphorylation.
4. NADH also plays a role in other metabolic processes, such as fatty acid synthesis and the metabolism of amino acids.
5. The balance between NAD+ and NADH levels in the cell is crucial for maintaining metabolic homeostasis and ensuring efficient energy production.

Review Questions

• How does NADH contribute to ATP production during cellular respiration?
  • NADH contributes to ATP production by serving as an electron donor in the electron transport chain. It donates electrons to Complex I, leading to a series of redox reactions that create a proton gradient across the mitochondrial membrane. This proton gradient drives ATP synthesis through ATP synthase during oxidative phosphorylation, ultimately converting energy stored in NADH into ATP.
• Discuss the importance of NADH in regulating metabolic pathways and its role in maintaining cellular energy balance.
  • NADH is vital in regulating various metabolic pathways by acting as a key electron carrier that helps manage redox states within cells. The ratio of NAD+/NADH influences metabolic flux through pathways like glycolysis and the citric acid cycle. When NADH accumulates, it can signal energy surplus and promote processes like fatty acid synthesis, while lower levels indicate energy deficits and increase catabolic activity to restore balance.
• Evaluate the significance of NADH levels in cellular metabolism and how disturbances in its balance can impact overall metabolic health.
  • NADH levels play a critical role in cellular metabolism by influencing energy production and various biosynthetic pathways. Disturbances in the NAD+/NADH ratio can lead to metabolic dysfunctions, contributing to conditions like insulin resistance and type 2 diabetes. An excess of NADH may inhibit critical enzymes involved in metabolism, while insufficient levels can impair ATP production and increase oxidative stress, highlighting its importance in maintaining overall metabolic health.

Related terms

Electron Transport Chain: A series of protein complexes located in the inner mitochondrial membrane that transfer electrons from NADH and FADH2 to oxygen, creating a proton gradient used for ATP synthesis.

Oxidative Phosphorylation: The metabolic pathway where ATP is produced using energy derived from the transfer of electrons through the electron transport chain, driven by the oxidation of NADH and FADH2.

Citric Acid Cycle: A series of enzymatic reactions occurring in the mitochondrial matrix that oxidizes acetyl-CoA to produce NADH, FADH2, and ATP, serving as key inputs for oxidative phosphorylation.