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- -happens in all green tissues
- -capture light energy to convert into CO2 into carbohydrates
Two steps of photosynthesis
- 1. light-dependant reactions
- 2.light-independant reactions
Where do the reactions happen?
- -inner membrane (thylakoids) of chloroplast
- -antenna pigments absorb light energy
- -transfer to reaaction center
- -start electron transport chain
- -At PSII, watermolecules are broken down to replace the lost electrons, and oxygen is released.
- -The electrons that pass along the transport chain are finally accepted by the electron carriermolecule named NADP, that produces NADPH.
- -dark reactions
- -The ATP and NADPH produced in light-dependent reactions are used here to produce sugarsfrom carbon dioxide. Also known as Calvin cycle,
CO2 Fixation Phase
An enzyme named Rubisco catalyzes the reaction between CO2 and a 5-carbon sugar named RuBP to generate a 3-carbon compound called PGA(Phosphoglyceric acid). As inorganic CO2 is converted to an organic form, this step is called as CO2 fixation.
PGA gains electrons and gets reduced to G3P (Glyceraldehyde-3-phosphate). This step requires energy. ATP produced in light reactions provide energy.This step also requires electrons. NADPH produced in light reactions provide electrons.
Most of the G3P produced in reduction phase are converted toRuBP to continue the cycle, to fix more CO2. Some G3P goes out of the Calvin cycle to produce glucose.
- -oxygen and glucose
- -oxygen comes from water breakdown
- -glucose comes from CO2
is the enzyme that catalyzes the critical step of fixing CO2 into organic form