P700

Definition

P700 is a chlorophyll pigment found in the reaction center of photosystem I (PSI) that plays a crucial role in the light-dependent reactions of photosynthesis. This pigment absorbs light energy, primarily at a wavelength of 700 nm, which initiates the process of converting solar energy into chemical energy. P700 is vital for the transfer of electrons in the photosynthetic electron transport chain, which ultimately leads to the production of ATP and NADPH.

5 Must Know Facts For Your Next Test

1. P700 is named for its peak absorption wavelength of 700 nm, which is in the red portion of the light spectrum.
2. In photosystem I, P700 works alongside another chlorophyll molecule, P700A, to absorb light and generate high-energy electrons.
3. The electrons energized by P700 are transferred to ferredoxin and then to NADP+, leading to the production of NADPH.
4. P700 becomes oxidized when it loses an electron, and it is subsequently reduced by electrons coming from the electron transport chain.
5. Deficiency or malfunction of P700 can significantly impair the efficiency of photosynthesis and reduce plant growth.

Review Questions

• How does P700 function within photosystem I during the light-dependent reactions?
  • P700 functions as the primary chlorophyll pigment in photosystem I, absorbing light energy primarily at 700 nm. When P700 absorbs this light, it becomes excited and loses an electron, initiating the flow of electrons through the electron transport chain. This process is crucial for the production of NADPH, as the energized electrons are passed to ferredoxin and ultimately reduce NADP+ to NADPH.
• Discuss the importance of P700's absorption characteristics in relation to the efficiency of photosynthesis.
  • P700's absorption characteristics at 700 nm are vital for optimizing the capture of solar energy for photosynthesis. This specific absorption allows plants to effectively utilize red light, which is abundant in sunlight. By having specialized pigments like P700 that target specific wavelengths, plants can maximize their energy intake, making photosynthesis more efficient and enhancing overall plant productivity.
• Evaluate the impact of impaired P700 function on a plant's ability to perform photosynthesis and its overall health.
  • If P700 is impaired or dysfunctional, a plant's ability to conduct photosynthesis is significantly compromised. Since P700 is crucial for generating high-energy electrons needed for NADPH production, any disruption will lead to decreased ATP and NADPH synthesis. This lack of essential products will hinder the plant's capacity to fix carbon dioxide during the Calvin cycle, ultimately affecting growth, development, and overall health. In severe cases, this could lead to wilting or even death due to insufficient energy supply.

Related terms

Photosystem I: A protein-pigment complex that uses light energy to generate high-energy electrons and is involved in the light-dependent reactions of photosynthesis.

Chlorophyll:

The green pigment found in plants, algae, and cyanobacteria that is essential for photosynthesis, allowing organisms to capture light energy.

Electron Transport Chain: A series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors through redox reactions, releasing energy used to create ATP.