Photosynthesis PQ

Question 1

In photosynthesis, which chemicals are needed for the light dependent reaction? [1]

Answer 1

NADP, ADP, Pi and water

Question 2

Describe what happens during photoionisation in the light-dependent reaction [2]

Answer 2

• chlorophyll absorbs light
• electrons are lost

Question 3

The diagram shows the chromatogram produced.
Explain why the student marked the origin using a pencil rather than using ink [1]

Answer 3

ink and pigments would mix

Question 4

The diagram shows the chromatogram produced.
Describe the method the student used to separate the pigments after the solution of pigments had been applied to the origin [2]

Answer 4

• level of solvent below origin/line
• remove before solvent reaches top

Question 5

The pigments in leaves are different colours. Suggest and explain the advantage of having different coloured pigments in leaves [1]

Answer 5

absorb more wavelengths of light for photosynthesis

Question 6

Heat stress decreases the light-dependent reaction of photosynthesis. Explain why this leads to a decrease in the light- independent reaction [2]

Answer 6

• less ATP
• less reduced NADP

Question 7

A decrease in the activity of the enzyme rubisco would limit the rate of photosynthesis, explain why [2]

Answer 7

• less carbon dioxide reacts with RuBP
• less GP

Question 8

Where precisely is rubisco found in a cell [1]

Answer 8

stroma of chloroplast

Question 9

In natural ecosystems, most of the light falling on producers Is not used in photosynthesis. Suggest two reasons why [2]

Answer 9

1- light is reflected
2- light is wrong wavelength

Question 10

The light absorbed by chlorophyll is used in the light-dependent reaction. Name two products of the light-dependent reaction that are required for the light-independent reaction [2]

Answer 10

1- ATP
2- Reduced NADP

Question 11

Atrazine binds to proteins in the ETC in chloroplasts of weeds, reducing the transfer of electrons down the chain. Explain how this reduces the rate of photosynthesis in weeds [4]

Answer 11

• reduced transfer of protons across thylakoid membrane
• so less ATP produced
• so less reduced NADP produced
• so light-independent reaction slows

Question 12

When treated with Atrazine, weeds have been shown to give off small amounts of heat, suggest an explanation for this observation [1]

Answer 12

idea that energy is released from high energy / excited electrons that were lost from chlorophyll