NADH

Definition

NADH, or nicotinamide adenine dinucleotide (reduced form), is a coenzyme that plays a crucial role in cellular metabolism, particularly in the processes of glycolysis and the citric acid cycle. It acts as an electron carrier, accepting electrons during metabolic reactions and becoming reduced to NADH, which can then donate these electrons to the electron transport chain. This process is essential for the production of ATP, the energy currency of cells, through oxidative phosphorylation.

5 Must Know Facts For Your Next Test

1. NADH is produced during glycolysis when glucose is broken down into pyruvate, yielding two molecules of NADH per glucose molecule.
2. In the citric acid cycle, each acetyl-CoA generates three NADH molecules as it undergoes a series of transformations.
3. NADH is essential for driving the electron transport chain, where it donates its electrons to complex I, facilitating the production of ATP through oxidative phosphorylation.
4. The conversion of NAD+ to NADH during metabolic reactions also plays a key role in regulating metabolic pathways and maintaining redox balance within cells.
5. The regeneration of NAD+ from NADH is critical for glycolysis to continue; without sufficient NAD+, glycolysis would halt and energy production would decline.

Review Questions

• How does NADH function within glycolysis and the citric acid cycle to contribute to cellular respiration?
  • In glycolysis, NADH is generated when glucose is converted into pyruvate, allowing for the transfer of electrons that ultimately helps produce ATP. Similarly, in the citric acid cycle, each turn produces three NADH molecules per acetyl-CoA. These NADH molecules serve as key electron carriers that transfer electrons to the electron transport chain, significantly impacting ATP generation during cellular respiration.
• Discuss the role of NADH in the electron transport chain and its importance for ATP production.
  • NADH plays a pivotal role in the electron transport chain by donating its electrons to complex I. This donation initiates a series of redox reactions that lead to the pumping of protons across the inner mitochondrial membrane, creating a proton gradient. The energy stored in this gradient is then used by ATP synthase to produce ATP during oxidative phosphorylation. Without NADH, there would be a significant reduction in ATP production as the electron transport chain would be compromised.
• Evaluate how disruptions in NADH production can affect overall cellular metabolism and energy balance in organisms.
  • Disruptions in NADH production can severely impact cellular metabolism and energy balance. For instance, if glycolysis or the citric acid cycle is inhibited due to low levels of NAD+, the regeneration of NADH will be compromised, leading to diminished ATP output from oxidative phosphorylation. This can result in an energy crisis within cells, affecting vital processes such as growth, repair, and overall homeostasis. Additionally, cells may shift towards less efficient anaerobic pathways to compensate, which can lead to lactic acid buildup and further metabolic complications.

Related terms

NAD+: The oxidized form of NADH that accepts electrons during metabolic reactions, crucial for energy production.

Citric Acid Cycle: A series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate derived from carbohydrates, fats, and proteins.

ATP: A high-energy molecule that serves as the primary energy carrier in cells, produced during cellular respiration.