Module 5- Photosynthesis

Question 1

6 marks

Describe the light- independent reaction of photosynthesis

Answer 1

1. Carbon dioxide reacts with RuBP
2. Produces two GP using Rubisco
3. GP reduced to TP
4. Using reduced NADP
5. Using energy from ATP
6. TP converted to useful organic substances like glucose

Question 2

6 marks

Desribe the role of electron trasnport chains in the light- dependent reactions of photosynthesis

Answer 2

1 electron transport chain accepts excited electrons
2 from chlorophyll
3 electrons lose energy along chain
4 ATP produced
5 from ADP and Pi
6 reduced NADP formed
7 when electrons and H+ combine with NADP
8 H+ from photolysis

Question 3

6 marks

Absorption of light energy and electron transfer chain

Answer 3

• Chlorophyll molecule absorbs light energy
• Pair of electrons become excited and move to higher energy level
• Electrons leave, chlorophyll molecule = oxidised
• Taken up by electron carrier molecule = reduced
• Move down chain in series of oxidation-reduction reactions
• Losing energy at each stage - used to combine ADP+Pi = ATP

Question 4

3 marks

What structural features of the thylakoids increase rate of photosynthesis

Answer 4

1. Contain photosynthetic pigments to absorb light energy
2. Large SA as discs stacked into grana to increase light absorption
3. Contain ATP synthase enzymes required to make ATP in LIR

Question 5

5 marks

Describe how light energy absorbed by chlorophyll molecules is used to synthesise ATP

Answer 5

Excitation of electrons raised to higher energy level
Electrons emimted from chlorophyll molecule
Electrons to electron transport chain
Loss of energy by electrons along electron transport chain
Energy lost by electrons is used to synthesise ATP; From ADP + Pi