P700

Definition

p700 is a pigment-protein complex found in the photosystem I (PSI) of plants, algae, and cyanobacteria, crucial for the light reactions of photosynthesis. It plays a key role in capturing light energy and transferring it to electrons during the process of converting solar energy into chemical energy.

5 Must Know Facts For Your Next Test

1. p700 is named for its maximum absorption peak at 700 nm in the red region of the light spectrum.
2. In photosystem I, p700 works alongside other pigments to enhance light absorption and energy transfer to electron carriers.
3. The reduction of NADP+ to NADPH is directly linked to the activity of p700, as it provides the high-energy electrons needed for this process.
4. When light photons are absorbed by p700, it becomes excited and transfers electrons to a primary electron acceptor, initiating a series of reactions in the electron transport chain.
5. Mutations or deficiencies in p700 can significantly affect the efficiency of photosynthesis and plant growth due to reduced electron transport and energy production.

Review Questions

• How does p700 contribute to the process of light reactions in photosynthesis?
  • p700 contributes to the light reactions by absorbing photons of light at a wavelength of 700 nm, which excites its electrons. These energized electrons are then transferred to a primary electron acceptor within photosystem I, initiating a chain reaction that ultimately leads to the production of NADPH. This process is essential for converting solar energy into chemical energy, which plants use for growth and metabolism.
• Discuss the relationship between p700 and chlorophyll within photosystem I.
  • p700 is essentially a specialized form of chlorophyll a that is integral to photosystem I. It plays a vital role in capturing light energy alongside other pigments within the complex. The interaction between p700 and other chlorophyll molecules maximizes light absorption, ensuring efficient energy transfer during the light reactions. This collaboration enhances the overall effectiveness of photosynthesis, particularly in producing high-energy molecules like NADPH.
• Evaluate the impact of deficiencies in p700 on plant photosynthesis and growth.
  • Deficiencies in p700 can severely limit the efficiency of photosynthesis by impairing electron transport processes. Without sufficient p700 activity, plants may struggle to convert light energy into chemical forms, resulting in lower ATP and NADPH production. This reduction directly impacts plant growth, health, and productivity since these energy-rich compounds are essential for various metabolic processes. Consequently, understanding p700's role helps highlight its importance for overall plant vitality and ecosystem functioning.

Related terms

Photosystem I: A protein complex in the thylakoid membranes that absorbs light energy, primarily at a wavelength of 700 nm, facilitating the production of NADPH.

Chlorophyll: The green pigment found in plants that absorbs light energy for photosynthesis, with p700 being a specific type of chlorophyll a associated with photosystem I.

Light Reactions: The first stage of photosynthesis that converts light energy into chemical energy in the form of ATP and NADPH, occurring in the thylakoid membranes.