NADPH

Definition

NADPH, or Nicotinamide Adenine Dinucleotide Phosphate, is a coenzyme that plays a crucial role in various metabolic processes, including the oxidation of alcohols, the biosynthesis of steroids, and the biosynthesis of fatty acids. It serves as a reducing agent, providing the necessary electrons for these important chemical reactions within the cell.

5 Must Know Facts For Your Next Test

1. NADPH is the reduced form of NADP+, and it is produced primarily through the Pentose Phosphate Pathway in the cytoplasm of cells.
2. In the oxidation of alcohols, NADPH provides the reducing power needed for the dehydrogenase enzymes to catalyze the conversion of alcohols to aldehydes or ketones.
3. During the biosynthesis of steroids, NADPH serves as a cofactor for the enzymes that catalyze the reduction and cyclization reactions, ultimately leading to the formation of complex steroid molecules.
4. In the biosynthesis of fatty acids, NADPH is required as a reducing agent for the enzymes that catalyze the addition of two-carbon units to the growing fatty acid chain.
5. The availability of NADPH is crucial for maintaining the cell's redox balance and protecting it from oxidative stress, as NADPH is used to regenerate the reduced form of glutathione, a key antioxidant.

Review Questions

• Explain the role of NADPH in the oxidation of alcohols.
  • NADPH plays a crucial role in the oxidation of alcohols to aldehydes or ketones, which is catalyzed by dehydrogenase enzymes. The NADPH provides the reducing power needed for these enzymes to facilitate the transfer of hydrogen atoms or electrons, ultimately leading to the oxidation of the alcohol group. This process is an important step in the metabolism of various alcohols and contributes to the overall regulation of cellular redox balance.
• Describe the function of NADPH in the biosynthesis of steroids.
  • During the biosynthesis of steroids, NADPH serves as a cofactor for the enzymes that catalyze the reduction and cyclization reactions. These enzymes utilize the reducing power of NADPH to convert simpler precursor molecules into the more complex steroid structures. The availability of NADPH is critical for maintaining the appropriate redox conditions necessary for the various enzymatic steps involved in the biosynthesis of a diverse range of steroid hormones and other important steroid-derived compounds.
• Analyze the role of NADPH in the biosynthesis of fatty acids and its broader implications for cellular metabolism.
  • In the biosynthesis of fatty acids, NADPH is required as a reducing agent for the enzymes that catalyze the addition of two-carbon units to the growing fatty acid chain. This process is essential for the de novo synthesis of fatty acids, which are crucial components of cellular membranes and serve as energy storage molecules. Beyond its direct role in fatty acid synthesis, the availability of NADPH is also critical for maintaining the cell's overall redox balance and protecting it from oxidative stress. NADPH is used to regenerate the reduced form of glutathione, a key antioxidant that helps neutralize reactive oxygen species and preserve the integrity of cellular components. Therefore, the regulation of NADPH levels has far-reaching implications for cellular metabolism, energy production, and overall cellular homeostasis.

Related terms

Oxidation-Reduction Reactions: Chemical reactions where one molecule loses electrons (oxidation) while another gains electrons (reduction), often facilitated by coenzymes like NADPH.

Dehydrogenase Enzymes: Enzymes that catalyze oxidation-reduction reactions, using coenzymes such as NADPH to transfer hydrogen atoms or electrons.

Pentose Phosphate Pathway:

A metabolic pathway that generates NADPH, which is then used in various biosynthetic processes and to maintain the cell's antioxidant defenses.