Photosynthesis
- Created by: caitlinamae
- Created on: 10-07-17 18:07
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- Photosynthesis
- Light independent reactions
- Occurs in the STROMA of chloroplast in light
- Requires a continuous source of ATP and reduced NADP from LD reactions
- Calvin Cycle
- Carbon fixation of RuBp catalysed by RUBISCO
- 6 carbon compound formed is unstable and breaks down into 2 x glycerate 3 phosphate (GP)
- GP is reduced to 12 x glyceraldehyde 3 phosphate (GALP)
- Hydrogen for reduction comes from reduced NADP from LD reactions. Energy for the reaction comes from the hydrolysis of ATP - ADP + Pi from LD reactions
- 2/12 GALPS is used in creation of carbohydrates (GL UCOSE) which can be converted to organic compounds such as amino acids or lipids.
- 10/12 GALPS are used in the recreation of RuBp. GALP is an isomer or RuBp. 10 GALPS rearrange then phosphorylation using hydrolysis of ATP creates RuBp.
- 2/12 GALPS is used in creation of carbohydrates (GL UCOSE) which can be converted to organic compounds such as amino acids or lipids.
- Hydrogen for reduction comes from reduced NADP from LD reactions. Energy for the reaction comes from the hydrolysis of ATP - ADP + Pi from LD reactions
- GP is reduced to 12 x glyceraldehyde 3 phosphate (GALP)
- 6 carbon compound formed is unstable and breaks down into 2 x glycerate 3 phosphate (GP)
- Carbon fixation of RuBp catalysed by RUBISCO
- Products used from LD Reaction: Reduced NADP and ATP
- Reduced NADP is the hydrogen source to reduce GP - GALP. It is a hydrogen carrier to ensure that the hydrogen doesn't react with oxygen as it is transferred from water to carbon dioxide.
- Occurs in the STROMA of chloroplast in light
- Light dependent reactions
- Occurs in the thylakoid membrane
- Products used from LI reaction: Oxidised NADP and ADP + Pi
- Energy from light excites two electrons from a chlorophyll molecules in PSII and raises them to a higher energy level - these electrons bring about reactions of LD stage
- Excited electrons from PSII are passed via electron carrier molecules which fill electron gaps in PSI. When a carrier accepts electrons, it is reduced. When electrons leave it is oxidised.
- Energy from the transit of these electrons is used to photophosphorylate ADP + Pi - ATP.
- Electron deficit in PSII is filled by 2 electrons from the photolysis of water
- The excited electrons from PSI are raised again to a higher energy level and these are passed to oxidised NADP, two at a time together with a hydrogen ion from photolysis forming reduced NADP
- Chemiosmotic Theory
- The excited electrons lose energy as they move along the electron transport chain. This energy is used to transport hydrogen protons via a proton pump into the thylakoid space from the stroma creating a higher concentration of protons in thylakoid space
- protons then move down their concentrationgradient into the stroma via the enzyme ATPase. the energy from this movement phosphorylates ADP + Pi - ATP
- The excited electrons lose energy as they move along the electron transport chain. This energy is used to transport hydrogen protons via a proton pump into the thylakoid space from the stroma creating a higher concentration of protons in thylakoid space
- Electron deficit in PSII is filled by 2 electrons from the photolysis of water
- Energy from the transit of these electrons is used to photophosphorylate ADP + Pi - ATP.
- Excited electrons from PSII are passed via electron carrier molecules which fill electron gaps in PSI. When a carrier accepts electrons, it is reduced. When electrons leave it is oxidised.
- Waste Product: Oxygen from photolysis
- Photolysis - splitting of water. products - 1/2 O2 molecule, 2 x H+ and 2e-
- photosystems:pigment molecules that trap light energy and funnel it to reaction centres, causing electrons to be raised to a higher energy level.
- Why does photosynthesis occur in chloroplasts?
- Compartmentalisation of these reactions in the chloroplast stroma means substrates and enzymes can be stored at concentrations which create efficient canalisation.
- Light independent reactions
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