Chapter 11: Photosynthesis

Question 1

during the light-independent reaction of photosynthesis, carbon dioxide is converted into organic substances. Describe how. [6 marks]

Answer 1

1. carbon dioxide combines with ribulose bisphophate/ RuBP
2. produces two glycerate 3 phosphate
3. GP reduced to triose phosphate
4. using reduced NADP
5. using energy from ATP
6. triose phosphate converted to glucose

Question 2

Crops use light energy to produce photosynthetic products. Describe how crop plants use light energy during the light-dependent reaction. [5 marks]

Answer 2

1. excites electrons / electrons removed from chlorophyll
2. electrons move along carriers/electron transfer chain releasing energy
3. energy used to join ADP + Pi to form ATP
4. photolysis of water produces protons, electrons and oxygen
5. NADP reduced by electrons / electrons and protons / hydrogen

Question 3

During photosynthesis, oil-palm trees convert carbon dioxide into organic substances. Describe how. [6 marks]

Answer 3

1. carbon dioxide combines with ribulose bisphosphate
2. produces two molecules of glycerate 3 phosphate
3. reduced to triose phosphate
4. using reduced NADP
5. using energy from ATP
6. triose phosphate converted to other organic substances
7. in light independent reaction

Question 4

describe the light-independent reaction of photosynthesis. [6 marks]

Answer 4

1. carbon dioxide combines with ribulose bisphosphate
2. produces two glycerate 3 phosphate using rubisco
3. GP reduced to triose phosphate
4. using reduced NADP
5. using energy from ATP
6. triose phosphate converted to glucose

Question 5

Energy enters most ecosystems through the light-dependent reaction of photosynthesis. Describe what happens during the light-dependent reaction. [5 marks]

Answer 5

1. chlorophyll absorbs light energy
2. excites electrons / electrons removed
3. electrons move along carriers / electron transport chain releasing energy
4. energy used to join ADP + Pi to form ATP
5. Photolysis of water produces protons, electrons and oxygen
6. NADP reduced by electrons / electrons and protons / hydrogen

Question 6

In the light-dependent reaction of photosynthesis, light energy generates ATP. Describe how. [5 marks]

Answer 6

1. light energy excites / raises energy level of electrons in chlorophyll
2. electrons pass down electron transfer chain
3. electrons reduce carriers / passage involves redox reactions
4. electron transfer chain / role of chain associated with chloroplast membranes
5. energy released / carriers at decreasing energy levels
6. ATP generated from ADP and phosphate

Question 7

The concentrations of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours. Use your knowledge of photosynthesis to describe these changes and explain why they occur. [5 marks]

Answer 7

1. high concentration of carbon dioxide linked with night
2. no photosynthesis in dark
3. plants respire
4. In light net uptake of carbon dioxide by plants / plants use more carbon dioxide than they produce / rate of photosynthesis greater than rate of respiration
5. decrease in carbon dioxide concentration with height
6. at ground level fewer leaves / less photosynthesizing tissue / more animals / less light

Question 8

In the light-independent reaction of photosynthesis, the carbon in carbon dioxide becomes carbon in triose phosphate. Describe how. [5 marks]

Answer 8

1. carbon dioxide combines with ribulose bisphosphate
2. to produce two molecules of glycerate 3 phosphate
3. reduced to triose phosphate
4. requires reduced NADP
5. energy from ATP