Which occurs during the light reaction of photosynthesisa)Chlorophyll ...
The chlorophyll pigments which are excited give up their electrons and to compensate for the loss of electrons, water is split to release four H+ ions and four electrons and O2. The electrons that are lost from the PSII enter into an electron transfer chain or ETC.
Which occurs during the light reaction of photosynthesisa)Chlorophyll ...
The light reaction of photosynthesis is the first stage of the process, which occurs in the thylakoid membrane of the chloroplasts. During this reaction, light energy is converted into chemical energy in the form of ATP and NADPH, which are used in the second stage of photosynthesis, known as the dark reaction or the Calvin cycle.
Explanation:
1. Light energy absorption:
- Chlorophyll, the primary pigment responsible for capturing light energy, absorbs light from the visible spectrum (mainly red and blue wavelengths).
- This energy excites electrons in the chlorophyll molecules to a higher energy level.
2. Splitting of water:
- As a result of light energy absorption, water molecules are split into hydrogen ions (H+), electrons (e-), and oxygen (O2).
- This process is called photolysis or photooxidation of water.
- The oxygen released during this reaction is the source of atmospheric oxygen.
3. Formation of ATP:
- The excited electrons from chlorophyll are transferred through a series of electron carriers in the thylakoid membrane.
- As the electrons move through these carriers, energy is released and used to pump protons (H+) from the stroma to the thylakoid lumen, creating a proton gradient.
- The flow of protons back into the stroma through ATP synthase enzyme leads to the synthesis of ATP (adenosine triphosphate) from ADP (adenosine diphosphate) and inorganic phosphate (Pi).
- This process is called photophosphorylation.
4. Formation of NADPH:
- In addition to ATP production, the excited electrons from chlorophyll are also passed on to a molecule called NADP+ (nicotinamide adenine dinucleotide phosphate), along with a hydrogen ion (H+).
- This transfer of electrons and hydrogen ions results in the formation of NADPH, which is a high-energy molecule that carries reducing power for the Calvin cycle.
In summary, during the light reaction of photosynthesis, chlorophyll absorbs light energy, water molecules are split to release oxygen, ATP is generated through photophosphorylation, and NADPH is formed by transferring excited electrons and hydrogen ions. These products, ATP and NADPH, are then used in the dark reaction of photosynthesis to convert carbon dioxide into glucose and other organic compounds.