17.4 Limiting factors affecting photosynthesis

Question 1

How does light intensity affect rate of photosynthesis?

Answer 1

• As light intensity increases, ATP and reduced NADP produced at a higher rate.

Question 2

How does carbon dioxide concentration affect rate of photosynthesis?

Answer 2

• Increasing the carbon dioxide concentration increases the rate of carbon fixation in the Calvin cycle and therefore the rate of TP production.

Question 3

How does temperature affect rate of photosynthesis?

Answer 3

• As temperature increases, the rate of enzyme activity increases until the point at which proteins denature.
• An increase in temperature increases the rates of enzyme-controlled reactions in photosynthesis, such as carbon fixation.

Question 4

What effect will reducing light intensity have on the Calvin cycle?

Answer 4

• Reducing light intensity will reduce the rate of light-dependent stage of photosynthesis.
• This reduces the quantity of ATP and reduced NADP produced.
• ATP and reduced NADP are needed to convert GP to TP.
• The concentration of GP will therefore increase and concentration of TP will decrease.
• As there is less TP to regenerate RuBP, concentration of RuBP decreases.
• Reverse will happen for when light intensity is increased

Question 5

What effect does carbon dioxide concentration have on the Calvin cycle?

Answer 5

• Low concentrations will lead to reduced concentrations of GP and TP as there is less carbon dioxide to be fixed.
• Concentration of RuBP will increase as it is still being formed from TP but not being used up to fix carbon

Question 6

What effect does temperature have on the Calvin cycle?

Answer 6

• At lower temperatures enzyme and substrate molecules have less kinetic energy resulting in fewer successful collisions and a reduced rate of reaction.
• This means decreasing temperatures results in lower concentrations of GP, TP and RuBP.