Topic 5

Question 1

Describe light -dependant reaction 5

Answer 1

-excites electrons
-electrons move along the etc releasing energy
-energy used to join ADP+ pi to form ATP
-photolysis of water produces protons , electrons and oxygen
-NADP reduced by electrons

Question 2

Describe what happens during photoionisation in the light dependant reaction (2 marks )

Answer 2

-chlorophyll absorbs light
-electrons are lost

Question 3

Which chemicals are needed for light dependant reaction ?

Answer 3

NADP , ADP , pi and water

Question 4

Explain why the student marked the origin using a pencil rather than using ink (1 mark)

Answer 4

ink and leaf pigments would mix

Question 5

Describe the method the student would used to separate the pigments after the solution of pigments had been applied to the origin (2 marks)

Answer 5

-level of solvent below origin line
-remove before solvent reaches the top

Question 6

The pigments in leaves are different colours . Suggest and explain the advantage of having different coloured pigments (1 mark )

Answer 6

Absorbs different wavelengths of light for photosynthesis

Question 7

A teacher studying these data with her students told her class that no definite conclusion could be drawn when comparing the mean values in the graph
Suggest why the teacher said this (2 marks (

Answer 7

• no standard deviation
• to show if overlap occurs so difference in means is not significant

Question 8

Atrazine binds to proteins in the etc in chlroplats weeds , reducing the transfer of electrons down the chain

Explain how this reduces the rate of photosynthesis in weeds (4 marks )

Answer 8

• reduces the transfer of protons across thylakoid membranes
• less atp is produced
  -less NADP produced
  -light independent reaction slows

Question 9

When treated with atrazine , weeds have been shows to give off small amounts of heat

Suggest and explanation for this observation (1 mark g

Answer 9

-energy is released from higher energy levels

Question 10

Explain why the scientist measured the rate of production of oxygen in this investigation (2 marks )

Answer 10

• oxygen is produced in light dependant reaction
  -the faster oxygen produce, the faster rate of reaction

Question 11

Describe the light independent reaction of photosynthesis (6 marks )

Answer 11

1. Carbon dioxide reacts with RuBP
2. Produces two GP using enzyme Rubisco
   3.GP reduced to TP
3. Using reduced NADP
4. Using energy from ATP
5. TP converted to glucose ( organic substances )

Question 12

Heat stress decreases light dependant reaction of photosynthesis

Explain why this leads to a decrease in the light independent reaction (2 marks )

Answer 12

1. Less ATP
2. Less reduced NADP

Question 13

A decrease in the activity of an enzyme rubisco would limit the rate of photosynthesis

Explain why (2 makrs )

Answer 13

1) less C02 reacts with RuBp
2) less GP