5.1.4 limiting factors and rate of photosynthesis

factors that could affect/ limit the rate of photosynthesis

• temperature - more kinetic energy, more ES complexes formed from rubisco so therefore more GP can be reduced to form more trios phosphate and so more used to regenerate RuBP

• CO2 concentration - form more gp meaning more gp reduced to form more triose phosphate to form more RuBP

• light intensity - chlorophyll absorbs more light energy, more electrons going down chain, more concentration gradient, more products formed so more ATP and NADP means more triose phosphate

• chlorophyll contration

high light intensity inhibits release of electrons from chlorophylll explain the results in figure 1 for 11.40 to 13.15 (4 marks)

in full sun there is lower uptake of carbon dioxide

less electrons moving down the electron transport chain less protons pumped into thylakoid/ lower H+ gradient

less electrons means less less electrons combine with NADP

*less ATP and NADPH produced

* less gp reduced to triose phosphate

less triose phosphate to regenerate RuBP

so less CO2 reacting with RuBP

Atrazine binds to proteins in the electron transfer chain in chloroplasts of weeds, reducing the transfer of electrons down the chain.

Explain how this reduces the rate of photosynthesis in weeds.

4 marks

rate od photosynthesis = measured by production of useful organic compounds (Calvin cycle)

• less electrons move down electron transport chain

• less protons pumped into the thylakoid

• lower proton concentration gradient

• less protons diffuse though ATP synthase

• less electrons combine with NADP

• Less ATP and NADP formed

• less gp reduced to triose phosphate

• less triose phosphate to make useful organic compounds like cellulose starch glucose to regenerate RuBP

limiting factors

what is in short supply - must have been something that was limiting the rate of photosynthesis

factors affecting the rate of photosynthesis (limiting factors)

CO2

temperature

light intensity

chlorophyll concentration

water availability

Limiting factor graphs on classroom - quite difficult - practice