Factors Affecting Photosynthesis- Photosynthesis

Question 1

What’s a limiting factor?

Answer 1

• when 1 of the factors needed for photosynthesis is in short supply, it reduces the rate of photosynthesis so becomes a limiting factor

Question 2

How is light intensity a limiting factor?

Answer 2

• As light intensity increases, more ATP and reduced NADP are formed in the light dependent reaction. These products are used in the light independent reaction so the rate of reduction of GP to TP increases, and so more RuBP would be regenerated from TP.
• if light intensity decreased, less ATP and reduced NADP are produced, which means that in the light independent stage the concentration of GP would increase as its not being reduced to TP. This means the conc of TP would decrease and so less RuBP is regenerated

Question 3

How is carbon dioxide concentration a limiting factor?

Answer 3

• An increased carbon dioxide concentration leads to increased rate of carbon fixation in the Calvin cycle, so more GP and TP produced and decreased conc of RuBP as it its being fixed with the carbon to form an unstable intermediate
• at low CO2 levels, there would be a reduced concentration of GP and TP, leading to an increase of RuBP as it is still being formed from TP but not being used to fix CO2.

Question 4

How is temperature a limiting factor?

Answer 4

• affects rate of enzyme controlled reactions
• at high temps, substrates and enzymes have more KE and so there’s more successful collisions to form enzyme-substrate complexes
• enzymes work at their optimum temp but above this they’re denatured so reaction stops
• at low temps, enzymes and substrates have low KE so less successful collisions and reduced ROR.

Eg for RuBisCo enzyme , low temps means reduced conc of GP,TP and RuBP because less carbon is fixed