Photosynthesis Flashcards
Limiting factor
- factor which controls the rate
- increasing this factor increases the rate of photosynthesis
- factor not at optimum
Two environmental conditions that need to be controlled when investigating photosynthesis
- temperature, use a water bath
- CO2, add sodium hydrogen carbonate
- pH, use a buffer
- wavelength of light, use filter
How determine rate of photosynthesis
- equilibrate before timing
- remove bubbles from capillary tube at start
- use syringe to move O2 bubble into capillary tube
- measure bubble
- determine volume of O2
- rate calculation
- repeats to give reliable results
How ATP is made available by reactions in the chloroplast
- light is absorbed (harvested)
- by chlorophyll pigments (a and b)
- electrons excited to higher energy level
- electrons passed to electron transport chain (electron carriers)
- energy is lost from electrons
- energy released is used for ATP production
- photophosphorylation
- photolysis (splitting of water) provides electron source
Two products of photosynthesis that require phosphate ions
- rNAD
- ATP
Describe one method you could use to estimate the abundance of an organism at intervals along a transect line
- place quadrat at intervals
- calculate percentage cover or count the number of vegetation present
- belt transect
- systematic sampling
Abiotic factor that could determine the distribution of plants
- pH
- water
- minerals and nurtients
Describe the process of non-cyclic phosphorylation
- takes place on the thylakoid membrane
- function is to produce ATP needed for synthesis of carbohydrates and for photolysis and to produce rNADP
- light energy absorbed by PSII
- light energy excites electrons in chlorophyll (photosystem) to a higher energy level
- electrons from PSII pass along electron carriers to PSI
- PSI absorbs light, electrons are boosted to a higher energy level and pass down electron carriers
- electrons lose energy which is used to synthesise ATP
- energy is use to transport H+ into the thylakoid, forming a proton gradient.
- H+ moves in the stroma via ATPase, which combines ADP + Pi to form ATP
- lost electrons from PSII need to be replaced, photolysis of water to produce 2e- and 2H+ and O2
- electrons excited from PSI combine with H+ from photolysis of water and are used to reduce NADP
Describe what happens to the products of non-cyclic phosphorylation
- oxygen produced diffuse out of leaf or used in respiration
- ATP and rNADP enters the calvin cycle (light independent stage)
- used to synthesise carbohydrates
Describe the process of the light independent reaction
- takes place in the stroma
- function to reduce CO2 to form carbohydrates
- CO2 enters leaf through stomata and diffuses to stroma
- CO2 combines with 5C RuBP, catalysed by RuBISCO, forming a 6C compound
- 6C compound is unstable and breaks down in two 3C GP
- 3C GP is reduced to 3C GALP, using ATP and rNADP from light dependent reaction (forming ADP + Pi and NADP)
- cycle has to turn 6 times to produce one molecule of glucose
- 2/12 GALP are used to form 6C sugar
- 10/12 GALP are used to regenerate 5C RuBP using ATP from light dependent reaction
What can GALP and GP be used to synthesise
- amino acids
- nucleic acids
- carbohydrates
- lipids
Structure of a chloroplast
- stroma
- starch grain
- thylakoid (membrane) / chlorophyll
- granum
Where is oxygen produced in the chloroplast
- thylakoid (O2 formed from photolysis of water)
Explain how oxygen is produced in chloroplasts during photosynthesis
- photolysis of water (splitting of water using light energy)
- release of electrons to chlorophyll (to PSII) to replace lost electrons
- release of H+ ions
- release of oxygen
Describe and explain the effect of high concentrations of oxygen on the rate of carbohydrate production in a chloroplast
- a high oxygen concentration reduces production of carbohydrates
- more oxygen, less CO2 in atmosphere
- less carbon available for reduction to carbohydrate
- less CO2 is fixed
- RuBP is required to combine with CO2
- calvin cycle cannot occur
- enzyme RuBISCO cannot function
