Photosynthesis

Question 1

Balance equation for photosynthesis

Answer 1

6CO2 + 6H2O ——> C6H12O6 + 6O2

Question 2

Explain how photosynthesis is important for life on earth

Answer 2

Provides oxygen and food

Question 3

Experiment to investigate the effect of light intensity

Answer 3

• No. of bubbles of gas released per minute from Elodea is counted to calculate rate of photosynthesis
• Excess sodium bicarbonate ensures constant CO2 concentrations
• Water bath ensures a constant temperature
• Light intensity varied by altering the distance between the lamp and the apparatus
• Results indicate that increasing light intensity increases photosynthesis

Question 4

Function of chlorophyll and where is it found

Answer 4

Absorbs light energy

Chloroplasts in the cell

Question 5

Products of the splitting of water during the light stage of photosynthesis

Answer 5

ATP
NADPH
Oxygen

Question 6

What happens to the end products of the light stage

Answer 6

ATP - supplies energy for the dark stage
NADPH - supplies protons and energised electrons for the dark stage
Oxygen - used for respiration or released

Question 7

Describe the pathways involved in the light stage

Answer 7

Cyclical electron flow - ATP made using light energy, involves electrons from chlorophyll flowing to electron acceptors and returning to chlorophyll
Non-Cyclic electron flow - light energy converted to ATP and NADPH, electrons flow from chlorophyll to electron acceptors and doesn’t return to chlorophyll

Question 8

Describe the dark stage

Answer 8

Does not require light and takes place in the chloroplast

• NADPH releases H+(Hydrogen ions) and 2 electrons
• CO2 combines with th H+ and electrons
• Energy provided by ATP converting to ADP
• Glucose made
• ADP and NADP+ return to light stage

Question 9

Balanced equation for the splitting of water

Answer 9

2H20 —light—> 4H(+) + 4e(-) + O2

Question 10

Equation of cyclic electron flow

Answer 10

ADP + energy + P —-> ATP + water

Question 11

Equation of non-cyclic electron flow (3)

Answer 11

• ADP + energy + P —-> ATP + water
• NADP(+) + 2 electrons(2e-) —–> NADP(-)
• NADP(-) + proton (H+) —-> NADPH

Question 12

Equation of the dark stage

Answer 12

ATP + water —-> ADP + P +energy