Photosynthesis Flashcards
What are the two main stages of photosynthesis?
- Light-dependent stage
- Light independent stage
Where does the light-dependent stage occur in the chloroplast?
- Within and across the thylakoid membranes
Where does the light-independent stage occur in the chloroplast?
-Occurs in the Stroma
Describe 2 ways in which the thylakoids are adapted to their function
- Contains Electron carries (ATP synthase)
- Large SA to volume ratio for light absorption
- Contains Photosystems
Why is there CO2 present in the gas collected?
-CO2 is present in the atmosphere
-CO2 produced during respiration
-
Suggest how deep aquatic plants are adapted
- In deeper waters, there is low light intensity
- The light-absorbing pigment absorbs the wavelength that penetrates deeper into the water
What 2 products are used up in the Calvin cycle?
- ATP
- NADPH (reduced NADP)
What is photorespiration?
- Wasteful pathway where the Rubisco enzyme acts on oxygen instead of CO2
- High concentrations of O2
Compensation point
-Point in which the rate of photosynthesis is equal to the rate of respiration
One way of working out the compensation point
-measuring the rate of oxygen production for an increase I light intensity
Granum
Thylakoid stack
Chloroplast info
-Contain photosynthetic pigments that absorb light energy which is needed for photosynthesis
Primary pigments
-Reaction centres where electrons are excited during LDS
Accessory pigments
- make up light harvesting systems
- Transfer light energy to allow for electron excitement
Photosystem
-Protein and pigment is called a photosystem
PSI
- p700
- absorbs light best at the 700 nm wavelength
- Used in CYCLIC and NON-CYCLIC phosphorolysation
PSII
- p680
- absorbs light best at 680 nm wavelength
- For Non-Cyclic phosphorolysation
Photolysis
-H2O is split into 1/2 (O2) + (H+) + (e-) in the presence of light
What happens in the LDS?
- Making ATP from ADP
- NADP -> NADPH (reduced NADP)
- Photolysis
Explain Non-cyclic photo phosphorylation
- Photolysis of water produces H+ ions, electrons and a biproduct O2
- Light energy excites electrons in chlorophyll and they get passed along an electron transport chain to PSII
- The energy from the excited electrons is used to make ATP, H+ move down a conc gradient into the stroma via ATP synthase (energy from this movement is used to make ATP from ADP)
- PSI excites the electron to an even higher energy level and this is then used to make NADPH in the stroma
Cyclic Photophosphrolysation
- Uses only PSI
- Only produces ATP
- Electrons are recycled
- Produces small amounts of ATP
Limiting factors
- Light intensity
- CO2 conc
- Water stress
- Temperature
- Wavelength
Effect of Temperature on Phoyosynthesis
Low: less reactions catalysed by Rubisco (becomes inactive)
High: Rubisco becomes denatured
- Thylakoid & Chloroplast membranes may be damaged
- Stomata close
- Chlorophyll could be damaged
