Q: What is the chemical equation of photosynthesis?
A: 6 Co2 + 12 H2O + light ----> C6G12O6 + 6 02 + 6 H2O
Q: What are the two stages of photosynthesis?
A: The light reactions and the Calvin cycle (dark reactions)
Q: How does the excitation of chlorophyll by light work?
A: A pigment goes from a ground state to an excited state when a photon boosts one of its electrons to a higher-energy orbital. This excited state is unstable. Electrons from isolated pigments tend to fall back to the ground state, giving off heat and/or light.
1. Photosynthesis converts light energy to the chemical energy of food.
2. The light reactions convert solar energy to the chemical energy of ATP and NADPH.
3. The Calvin cycle uses ATP and NADPH to convert CO2 to sugar.
4. Alternative mechanisms of carbon fixation have evolved in hot, arid climates.
5. Organic compounds produced by photosynthesis provide the energy and building material for ecosystems.
This picture shows the chemiosmosis in Photosynthesis, how the removed concentrated hydrogene ions in the thylakoid space from the stroma as electrons pass from carrier to carrier are moved out into stroma by ATP synthase.
In summary, photosynthesis is a process in which energy is converted to chemical energy and used to produce organic compounds. In plants, photosynthesis occurs within the chloroplasts. Photosynthesis consists of two stages, the light reactions and the dark reactions.
The light reactions take place in the presence of light. The dark reactions do not require direct light, however in most plants, they occur during the day.
Light reactions occur mostly in the thylakoid stacks of the grana. Here, sunlight is converted to chemical energy in the form of ATP (free energy containing molecule) and NADPH (high energy electron carrying molecule). Chlorophyll absorbs light energy and starts a chain of steps that result in the production of ATP, NADPH, and oxygen (through the splitting of water). Oxygen is released through the stomata. Both ATP and NADPH are used in the dark reactions to produce sugar.
Dark reactions occur in the stroma. Carbon dioxide is converted to sugar using ATP and NADPH. This process is known as carbon fixation or the Calvin cycle. Carbon dioxide is combined with a 5-carbon sugar creating a 6-carbon sugar. The 6-carbon sugar is eventually broken-down into two molecules, glucose and fructose. These two molecules make sucrose or sugar.
Autotroph: an organism that obtains organic food molecules without eating other organisms or substances derived from other organisms. Autotrophs use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones.
Outer and inner membranes: protective coverings that keep chloroplast structures enclosed.
Stroma: dense fluid within the chlroplast. Site of conversion of carbon dioxide to sugar.
Thylakoid: flattened sac-like membrane structures. Site of conversion of light energy to chemical energy.
Grana: Dense layered stacks of thylakoid sacs. Sites of conversion of light energy to chemical energy.
Chlorophyll: a green pigment within the chloroplast. Absorbs light energy.
Wavelength: the distance between the crests of electromagnetic waves
C3 plant: A plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate.
C4 plant: A plant in which the Calvin cycle is preceded by reactions that incorporate CO2 into a four-carbon compound, the end product of which supplies CO2 for the Calvin cycle.
CAM plant: A plant that uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions. In this process, carbon dioxide entering open stomata during the night is converted to organic acids, which release CO2 for the Calvin cycle during the day, when stomata are closed.
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