key term - NADPH

Definition

NADPH, or nicotinamide adenine dinucleotide phosphate, is a coenzyme that acts as an electron carrier in the cell. It plays a crucial role in anabolic reactions, where it provides the reducing power necessary for biosynthesis and helps to drive processes such as the Calvin cycle and carbon fixation in photosynthesis. By delivering electrons and protons, NADPH supports the conversion of carbon dioxide into glucose and other organic compounds.

5 Must Know Facts For Your Next Test

1. NADPH is generated during the light reactions of photosynthesis when NADP+ accepts electrons and protons, facilitated by the enzyme NADP+ reductase.
2. The main function of NADPH is to provide reducing power for the synthesis of carbohydrates during the Calvin cycle.
3. In addition to photosynthesis, NADPH is also important in various biosynthetic pathways, including fatty acid synthesis and nucleotide synthesis.
4. NADPH helps protect cells from oxidative stress by providing reducing equivalents that are used in detoxifying reactive oxygen species.
5. The balance between NADP+ and NADPH is crucial for maintaining cellular redox state and overall metabolic health.

Review Questions

• How does NADPH contribute to the process of carbon fixation within the Calvin cycle?
  • NADPH provides the necessary reducing power for the Calvin cycle, allowing for the conversion of carbon dioxide into glucose. During this process, NADPH donates electrons to 3-phosphoglycerate (3-PGA), reducing it to glyceraldehyde-3-phosphate (G3P). This step is vital because G3P can be further processed to form glucose and other carbohydrates, making NADPH essential for synthesizing organic molecules from inorganic carbon.
• Discuss the role of NADPH in protecting cells from oxidative damage during photosynthesis.
  • NADPH plays a protective role by supplying reducing equivalents that help neutralize reactive oxygen species (ROS) generated during photosynthesis. When chlorophyll absorbs light energy, excess energy can lead to the formation of ROS, which can damage cellular components. By providing electrons through antioxidant pathways, NADPH contributes to maintaining cellular integrity and function, thus preventing oxidative stress and potential cellular damage.
• Evaluate the importance of NADPH in both photosynthetic and non-photosynthetic organisms' metabolic processes.
  • NADPH is crucial not only for photosynthetic organisms, where it facilitates carbon fixation in the Calvin cycle, but also for non-photosynthetic organisms. In these organisms, NADPH is involved in various biosynthetic processes such as fatty acid synthesis and nucleotide synthesis. Furthermore, it plays a key role in cellular defense mechanisms against oxidative stress by participating in detoxification reactions. The versatility of NADPH underscores its central role in supporting life across different biological systems.

Related terms

NADP+: NADP+ is the oxidized form of NADPH and serves as an electron acceptor during the light reactions of photosynthesis.

Calvin Cycle:

The Calvin Cycle is a series of biochemical reactions that occur in the stroma of chloroplasts, using ATP and NADPH to convert carbon dioxide into glucose.

Photosynthesis:

Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose, utilizing water and carbon dioxide.