3.5.1 Photosynthesis

Question 1

Light Dependent Reaction – Describe the process (6)

Answer 1

Mark scheme
Light Dependent Reaction –
Describe the process (6)
1. Excites electrons / electrons removed (from chlorophyll);
2. Electrons move along carriers/electron transfer chain releasing energy;
Accept: movement of H+/protons across membrane releases energy.
Reject: ‘produces energy’ for either mark but not for both.
3. Energy used to join ADP and Pi to form ATP;.
4. Photolysis of water produces protons, electrons and oxygen;
5. NADP reduced by electrons / electrons and protons / hydrogen;

Question 2

Light Dependent Reaction. Describe the electron transport chain (5)

Answer 2

1. Excites electrons (from chlorophyll);
2. Electrons move along carriers/electron transfer chain releasing energy;
3. Energy used to join ADP and Pi to form ATP;
4. Photolysis of water produces protons, electrons and oxygen;
5. NADP reduced by electrons;

Question 3

Light Independent Reaction.
Describe the Calvin Cycle (6)

Answer 3

1. Carbon dioxide combines with RuBP;
2. Produces two GP;
3. GP reduced to TP;
4. Using reduced NADP;
5. Using energy from ATP;
6. TP converted to glucose / hexose / RuBP / ribulose bisphosphate / named organic substance;

Question 4

Why weedkillers cause plants to
give off heat? (2)

Answer 4

1. Energy is released from high energy/excited electron/s (that were lost from chlorophyll
2. This energy which should be used to form ATP, cannot do this as the weedkiller blocks the ETC, (so the energy
   is lost as heat)

Question 5

Why does increased light intensity
stimulate plant growth? (5)

Answer 5

1. Have faster production of ATP and reduced NADP;
2. (So) have faster/more light-independent reaction;
3. (So) produce more sugars that can be used in respiration;
4. (So) have more energy for growth;
5. Have faster/more synthesis of new organic materials;