Zusammenfassung der Ressource
Photosynthese
- Role of Photosynthesis
- Plants use it to make food
- Animals eat plants
- Produces O2
- Responsible for the formation of fossil fuels
- Equation
- 6CO2 + 6H2O + light ------> C6H12O6 + 6O2 Chlorophyll
- Stages
- Light is absorbed
- Sunlight is trapped by chlorophyll
- Water is split
- Trapped sunlight is split into H2O
- 2H2O --> 4H+ + O2 + 4e- (photolysis)
- Products of splitting water
- e- = passed into chlorophyll
- H+ = released into a storage pool of H+ in chloroplast
- O2
- Pass from chloroplast to cytoplasm to atmosphere
- Used within cells of leaf in respiration
- Light energises electrons
- Some of the sunlight energy trapped by chlorophyll is passed onto electrons in chlorophyll to form high energy electrons
- Glucose is formed
- High energy electron from chlorophyll along with protons from pool of stored protons combine with CO2 to form glucose
- Sources of light, CO2 + H2O
- Light
- Sun
- Artificial in greenhouse
- CO2
- Air (via leaf))
- Produced by respiration
- Artificial: burning gas in greenhouse
- H2O
- Absorbed by plant from soil via roots, passed through stem + to leaves
- Light Stage
- Grana of chloroplast
- No enzymes
- Light is absorbed by a range of pigment clusters found in the chloroplast (green is reflected)
- Light is transferred to the electron that has been passed to the chlorophyll
- Chlorophyll is in the pigment cluster + is near an electron acceptor
- Pigment cluster absorbs as much light energy as possible --> chlorophyll --> electron
- Energised electron is passed to the electron acceptor which can than send it on 2 pathways
- Pathway 1
- Electrons pass from the 1st electron acceptor to a series of other electron acceptors + back to chlorophyll
- Electrons lose energy as they're passed
- Lost energy is used to join a phosphate + ADP = ATP (H2O is also formed)
- ADP + energy + P --> ATP + H2O
- Phosphorylation = addition of P to ADP
- Cyclic Phosphorylation
- Pathway 2
- 2 high energy electrons at a time pass from chlorophyll to electron acceptor + then along another series of electron acceptors
- Breaks up water
- Electrons don't return to original chlorophyll
- Energy lost is used to make ATP
- 2 e- combine with NADP+ to form NADP-
- Chlorophyll molecule is short of e- + gains more H+
- NADP- + H+ --> NADPH
- Non cyclic phosphorylation
- End products
- ATP provides energy for dark phase
- NADPH provides H+ and energised e- for dark phase
- O2 made by splitting of H2O
- Dark Stage
- Uses energy from breaking down of ATP --> ADP + P
- Uses hydrogen ions +e- from breaking down of NADPH --> NADP+ + 2e- + H+
- CO2 is reduced to C6H12O6
- Stroma of chloroplast
- Controlled by enzymes + can be affected by temp
- CO2 from air/respiration enters the chloroplast where it combines with H+ and e- to form glucose