Photosynthesis

Question 1

Describe how light energy absorbed by chlorophyll molecules is used to synthesise ATP (5)

Answer 1

• Excitation of chlorophyll due to absorbed light
• Electrons leave the chlorophyll
• Electrons enter the electron transport chain
• Loss of energy by electrons along the electron transport chain
• Energy lost by electrons used to synthesise ATP from ADP + Pi

Question 2

Where exactly in a cell is the enzyme Rubisco found? (1)

Answer 2

Stroma

Question 3

Explain why the increase in the dry mass of a plant over twelve months is less than the mass of hexose produced over the same period (3)

Answer 3

• Some glucose is used in respiration
• C02 produced is lost to air
• Some parts of the plant are eaten

Question 4

The products of the light-dependent stage are used in the light-independent stage of photosynthesis. What are these products used for? (1)

Answer 4

To incorporate carbon dioxide to make glucose

Question 5

Explain why the light-independent reaction slows down at low temperatures? (2)

Answer 5

• Enzymes are involved in the LIR
• Slower rate of enzyme activity
• Less kinetic energy (so fewer collisions)

Question 6

What process is the source of the ATP used in the conversion of glycerate-3-phosphate into triose phosphate? (1)

Answer 6

Light-independent reaction

Question 7

What proportion of triose phosphate molecules is converted to ribulose bisphosphate (RuBP)?

Answer 7

5/6

Question 8

Give two ways in which the hydrolysis of ATP is used in cells (2)

Answer 8

• Provide energy for other reactions like Active Transport

- To add phosphate to other substances and make them more reactive

Question 9

Describe how ATP is re-synthesised in cells (2)

Answer 9

• From ADP + Pi
• By ATP synthase
• During respiration

Question 10

What is the formula to work out magnification? (1)

Answer 10

Image size / Actual size

Question 11

In which part of the chloroplast do the light-dependent reactions occur? (1)

Answer 11

Thylakoid

Question 12

Describe what happens in the photolysis of water (2)

Answer 12

• Photolysis produces H+ and e-

- Oxygen is formed

Question 13

Describe how NADP is reduced in the light-dependent reaction of photosynthesis (2)

Answer 13

• NADP accepts electrons

- from the chlorophyll

Question 14

Describe the role of electron transport chains in the light-dependent reactions of photosynthesis (6)

Answer 14

• The electron transport chain accepts excited electrons
• from chlorophyll
• electrons lose energy along the chain
• ATP is produced
• from ADP + Pi
• reduced NADP formed when electrons (from ETC) and H+ combine with NADP

Question 15

Describe the light-independent reactions of photosynthesis and explain how they allow the continued synthesis of glucose (6)

Answer 15

• RuBP (5C) combines with CO2
• to form 2x GP (3C)
• 2 x TP (3C) to glucose
• using ATP
• and reduced NADP
• All RuBP is regenerated so glucose can be resynthesised

Question 16

Describe one function of reduced NADP in the light-independent reaction (1)

Answer 16

• Reduces GP to TP

Question 17

Describe one function of ATP in the light-independent reaction (1)

Answer 17

Provides energy for the conversion of GP to TP

Question 18

How many micrometres is there in one centimetre?

Answer 18

10,000

Question 19

During the light-independent reaction of photosynthesis, carbon dioxide is converted into organic substances. Describe how (6)

Answer 19

• CO2 combines with RuBP
• Produces 2x GP
• GP reduced to TP
• Using reduced NADP
• using energy from ATP
• TP converted to glucose

Question 20

In which part of the chloroplast does the light-independent reaction occur?

Answer 20

Stroma