What is the path that electrons take in C3 photosynthesis?
In C3 photosynthesis, the path that electrons take can be explained as follows:
1. Light Absorption: The process begins when photons of light are absorbed by chlorophyll molecules present in the chloroplasts of plant cells.
2. Excitation of Electrons: The absorbed light energy is used to excite electrons in the chlorophyll molecules, moving them to a higher energy state.
3. Electron Transport: The excited electrons are initially transferred to a molecule called plastoquinone (PQ) in the thylakoid membrane. From PQ, the electrons proceed to a series of electron carrier molecules known as the cytochrome b6f complex, which pumps protons (H+) across the thylakoid membrane.
4. Production of ATP: During electron transport, the cytochrome b6f complex transfers the electrons to a protein called plastocyanin (PC), which then passes the electrons to photosystem I (PSI). As the electrons move through PSI, they gradually lose energy, which is harnessed to generate adenosine triphosphate (ATP), an energy-rich molecule used by the plant.
5. NADPH Formation: After losing energy in PSI, the electrons are passed to another electron carrier molecule called ferredoxin (Fd). From Fd, the electrons proceed to an enzyme known as ferredoxin-NADP+ reductase (FNR), which transfers them to a molecule called nicotinamide adenine dinucleotide phosphate (NADP+), leading to the formation of nicotinamide adenine dinucleotide phosphate (NADPH). NADPH is used as a reducing agent in subsequent biochemical reactions.
The overall flow of electrons in C3 photosynthesis involves the movement of excited electrons from chlorophyll to various electron carrier molecules, leading to the formation of ATP and NADPH. These energy-rich molecules are then used in the subsequent steps of the photosynthetic process to fix carbon dioxide and produce carbohydrates.