Photosynthesis Flashcards
2 uses of ATP?
- Provides energy for active transport/protein synthesis
- Phosphorylation - binds to enzymes to lower Ea/make more reactive
Why is ATP useful? (6)
- Releases energy in small amounts
- Broken down in one step
- Makes energy rapidly available
- Phosphorylates/adds phosphate
- Makes substance more reactive
- Can be made again
Where does the light dependant reaction take place?
What does it need?
Granum
- Light energy
- Water
Where does the light independent reaction occur?
What is needed for the light independent reaction?
Stroma
- Carbon dioxide
- NADPH
- ATP
What happens in the light dependent reaction? (8)
- Chlorophyll absorbs light energy via photoionisation
- Excites electrons/ chlorophyll is oxidised
- Electrons move along the electrons transport chain releasing energy
- Energy released used to form proton gradient
- H+ ions diffuse through ATPsynthase (photophosphorylation)
- Providing energy to join ADP and Pi to form ATP
- Photolysis of water produces 2 protons, 2 e- and 1/2 O2
- NADP reduces by electrons
Photolysis equation?
In plants ATP is produced in the light dependent reaction.
Suggest why this is not a plants only source of energy? (4)
- Plants don’t photosynthesise in the dark
- Not all parts of the plant photosynthesise (roots)
- Plants require more ATP than produces in LDR
- ATP used in active transport
Describe the effect of introducing a herbicide on the electron transport chain? (4)
- Reduced transfer of protons across thylakoid membrane
- So less ATP produced
- Less NADPH
- So light independent reaction slows down
Describe the effect of introducing a herbicide on the electron transport chain? (4)
- Reduced transfer of protons across thylakoid membrane
- So less ATP produced
- Less NADPH
- So light independent reaction slows down
Describe the light-independent reaction? (6)
- Carbon dioxide combines with RuBP
- Produces 2 GPs using rubisco
- GP reduced to triose phosphate
- Using NADPH
- Using energy from ATP
- Triose phosphate is converted to RuBP
Where is rubisco found in a cell?
Stroma
Suggest + explain the advantage of plants having different coloured pigments in leaves?
Absorb different/more wavelengths of light for photosynthesis
What are the limiting factors for photosynthesis?
- Light intensity + wavelength
- CO2 concentration
- Temperature
The concentration of CO2 in the air at different heights above ground in a forest changes over a 24 hour period
Use your knowledge of photosynthesis to describe these changes + explain why they occur? (5)
- High conc. of CO2 linked with night/darkness
- No photosynthesis in dark/light required for photosynthesis
- In dark, plants respire
- Decrease in CO2 conc. with height
- At ground level fewer leaves/less light
