Ferredoxin-nadp+ reductase

Definition

Ferredoxin-NADP+ reductase (FNR) is an enzyme that catalyzes the reduction of NADP+ to NADPH, utilizing electrons transferred from ferredoxin in the light-dependent reactions of photosynthesis. This enzyme plays a crucial role in the electron transport chain, linking the photosystems to the production of NADPH, which is essential for the Calvin cycle in plants.

5 Must Know Facts For Your Next Test

1. FNR is located in the thylakoid membrane of chloroplasts where it plays a key role in linking light energy conversion to chemical energy storage.
2. The reduction of NADP+ to NADPH by FNR is vital for providing reducing power in the Calvin cycle, enabling the conversion of carbon dioxide into glucose.
3. FNR uses a two-electron transfer mechanism and is typically found in plants, algae, and some bacteria.
4. The activity of FNR is regulated by its interaction with ferredoxin, which carries electrons generated during light absorption in photosystem I.
5. Mutations or deficiencies in FNR can severely impact plant growth and development due to reduced NADPH production.

Review Questions

• How does ferredoxin-nadp+ reductase contribute to the overall process of photosynthesis?
  • Ferredoxin-nadp+ reductase facilitates the conversion of light energy into chemical energy by catalyzing the reduction of NADP+ to NADPH. This reaction is essential because NADPH provides the necessary reducing power for the Calvin cycle, where carbon dioxide is fixed into organic molecules. Without FNR's activity, the electrons harvested during the light-dependent reactions would not effectively contribute to synthesizing NADPH, significantly hindering photosynthesis.
• Discuss the role of ferredoxin in conjunction with ferredoxin-nadp+ reductase and its importance in the light-dependent reactions.
  • Ferredoxin acts as an electron carrier that receives electrons from photosystem I during the light-dependent reactions. Once it is reduced, ferredoxin then transfers these electrons to ferredoxin-nadp+ reductase. This transfer is critical because it allows FNR to perform its function of reducing NADP+ to NADPH. The ability of ferredoxin to shuttle electrons efficiently ensures that there is a continuous supply of NADPH for subsequent biochemical processes, particularly in carbon fixation.
• Evaluate how alterations in ferredoxin-nadp+ reductase activity might impact plant metabolism and growth.
  • Alterations in ferredoxin-nadp+ reductase activity can lead to significant disruptions in plant metabolism and growth due to decreased levels of NADPH. As NADPH is vital for various biosynthetic reactions, including fatty acid and nucleotide synthesis, any impairment in FNR could result in reduced energy storage and compromised cellular functions. Consequently, plants may exhibit stunted growth, poor reproductive success, and lower resilience against environmental stressors as their metabolic pathways become unbalanced without adequate NADPH production.

Related terms

Photosystem I:

A protein-pigment complex in plants that captures light energy and transfers electrons to ferredoxin, contributing to the electron transport chain.

NADPH:

Nicotinamide adenine dinucleotide phosphate, a crucial reducing agent produced during the light-dependent reactions and utilized in various biosynthetic pathways.

Electron Transport Chain: A series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions, ultimately leading to the synthesis of ATP and NADPH.