module 5 - 17.4 factors affecting photosynthesis Flashcards
what are the limiting factors affecting the rate of photosynthesis?
- light intensity
- light quality (what wavelengths)
- carbon dioxide concentration
- temperature
- stomatal status - open or closed
how is light intensity a limiting factor affecting the rate of photosynthesis?
as light increases, ATP and reduced NADP are produced at a higher rate
how is light quality a limiting factor affecting the rate of photosynthesis?
light with a higher proportion of energy concentrated in these wavelengths will produce a higher rate of photosynthesis.
how is carbon dioxide concentration a limiting factor affecting the rate of photosynthesis?
increasing the carbon dioxide concentration increases the rate of carbon fixation in the calvin cycle and increases rate of ATP
how is temperature a limiting factor affecting the rate of photosynthesis?
- affects rate of enzyme controlled reactions
- as temp increases, rate of anzyme activity increases until proteins denature
- increase in temp increases rate of enzyme controlled reactions in photosynthesis
how is stomatal status a limiting factor affecting the rate of photosynthesis?
- stomata close on leaves to avoid water loss through transpiration during dry weather
- closing stomata stops diffusion of carbon dioxide in plants, reducing rate of light independent reactions and stops photosynthesis
what will happen if light intensity is reduced from high to low? (effect on calvin cycle)
- rate of reaction of light dependent stage reduces
- concentration of ATP and reduced NADP will reduce
- conc. of GP increases as ATP and reduced NADP are needed to convert GP to TP so conc. of these molecules is reduces
- conc. of TP reduces as ATP and reduced NADP are needed to convert GP to TP and conc. od ATP and reduced NADP reduces
- conc. of RuBP reduces because of lower conc. of TP it’s made from
what will happen if the concentration of CO2 is reduced from high to low? (effect on calvin cycle)
- concentration of GP is reduced as there is less CO2 to be fixed
- conc. of TP is reduced as there is less GP that its made from
- conc. of RuBP increases due to lack of CO2 to be fixed
what will happen if temperature reduces? (effect on calvin cycle)
- reducing kinetic energy of all enzymes and substrates of Calvin Cyle
- reducing number of successful collisions between enzymes and substrates
- reducing overall rate of reaction of Calvin Cycle
- reducing conc. of GP, TP & RuBP
what will happen if temperature increases to high temperatures? (effect on calvin cycle)
- enzymes in Calvin Cyle will be irreversibly denatured
- reducing concentrations of GP, TP & RuBP
what does “fixed” mean?
adding hydrogen to inorganic carbon from reduced NAD
what is C4 photosynthesis?
- alternative to normal C3 photosynthesis
- called C4 as CO2 molecules are fixed to make a 4-carbon molecule, not by RUBISCO
what is carbon dioxide fixed by in C4 photosynthesis?
- enzyme called PEP CARBOXYLASE and produces 4-carbon OXALOACETATE
- PEP CARBOXYLASE has no affinity for oxygen
where is oxaloacetate transported in C4 photosynthesis?
- transported into bundle sheath cells around the vascular bundles
- it is then decarboxylated to produce carbon dioxide
what does RUBISCO convert carbon dioxide and RuBP into, after the oxaloacetate is decarboxylated? (C4 photosynthesis)
- converts them into the 6-carbon intermediate and 2 GP molecules
- this means RUBISCO is shielded form oxygen produced by photolysis in the chloroplast and also has high conc. of CO2
- the 2 GP is transported back to normal photosynthetic cells