Photosynthesis is a complex biochemical process that occurs in the chloroplasts of plants, algae, and some bacteria. It involves the conversion of light energy from the sun into chemical energy in the form of glucose (food) and the release of oxygen as a byproduct. The process can be summarized into two main stages:
1. Light-dependent reactions: These reactions occur in the thylakoid membrane of chloroplasts and require light energy to take place. The steps involved are:
- Absorption of light energy by chlorophyll pigments located in photosystems I and II.
- Water molecules are split through a process called photolysis, releasing electrons, protons (H+), and molecular oxygen (O2).
- The released electrons are used to generate ATP (adenosine triphosphate), an energy-rich molecule, through a process called electron transport chain.
- The protons generated from the splitting of water are used to create a proton gradient across the thylakoid membrane, which helps in the synthesis of ATP and a molecule called NADPH (nicotinamide adenine dinucleotide phosphate).
2. Calvin cycle (also known as the light-independent reactions or dark reactions): This cycle occurs in the stroma of chloroplasts and utilizes the products of the light-dependent reactions, ATP, and NADPH. The steps of the Calvin cycle are:
- Carbon dioxide (CO2) from the atmosphere enters the plant through tiny openings called stomata and is incorporated by an enzyme called Rubisco (ribulose biphosphate carboxylase/oxygenase).
- The CO2 is fixed into a five-carbon molecule known as RuBP (ribulose-1,5-bisphosphate).
- This initiates a series of chemical reactions where ATP and NADPH from the light-dependent reactions are utilized to convert the fixed carbon (CO2) into glucose (C6H12O6).
- The remaining molecules of RuBP are regenerated, allowing the cycle to continue.
Overall, the process of photosynthesis converts light energy, water, and carbon dioxide into glucose and oxygen. It is crucial for sustaining life on Earth as it provides the oxygen we breathe and acts as the primary source of energy for all living organisms.
What happens in the process of photosynthesis?
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