Q1.
Photosynthesis uses carbon dioxide to make glucose.
(a)     (i)      Complete the equation for photosynthesis.
carbon dioxide + _____________ glucose + _____________
(2)
(ii)     What type of energy does a plant use in photosynthesis?
______________________________________________________________
(1)
(iii)    Which part of a plant cell absorbs the energy needed for photosynthesis?
______________________________________________________________
(1)
(b)     The graph shows the effect of the concentration of carbon dioxide on the rate of photosynthesis in tomato plants at 20 °C.
 
(i)      What is the maximum rate of photosynthesis of the tomato plants shown in the graph?
_____________ arbitrary units
(1)
(ii)     At point X, carbon dioxide is not a limiting factor of photosynthesis.
Suggest one factor that is limiting the rate of photosynthesis at point X.
______________________________________________________________
(1)
(c)     A farmer plans to grow tomatoes in a large greenhouse.
The concentration of carbon dioxide in the atmosphere is 0.04%.
The farmer adds carbon dioxide to the greenhouse so that its concentration is 0.08%.
(i)      Why does the farmer use 0.08% carbon dioxide?
Tick () one box.
 
To increase the rate of growth of the tomato plants		
To increase the rate of respiration of the tomato plants		
To increase water uptake by the tomato plants		
(1)
(ii)    Why does the farmer not use a concentration of carbon dioxide higher than 0.08%?
Tick () two boxes.
 
Because it would cost more money than using 0.08%		
Because it would decrease the temperature of the greenhouse		
Because it would not increase the rate of photosynthesis of the
tomato plants any further		
Because it would increase water loss from the tomato plants		
(2)
(Total 9 marks)
Q2.
The diagram below shows a single-celled alga which lives in fresh water.
 
(a)     Which part of the cell labelled above:
(i)      traps light for photosynthesis
______________________________________________________________
(1)
(ii)     is made of cellulose?
______________________________________________________________
(1)
(b)     In the freshwater environment water enters the algal cell.
(i)      What is the name of the process by which water moves into cells?
______________________________________________________________
(1)
(ii)     Give the reason why the algal cell does not burst.
______________________________________________________________
______________________________________________________________
(1)
(c)     (i)      The alga can photosynthesise.
Complete the word equation for photosynthesis.
water + _______________  _______________ + oxygen
(2)
(ii)     The flagellum helps the cell to move through water. Scientists think that the flagellum and the light-sensitive spot work together to increase photosynthesis.
Suggest how this might happen.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
(2)
(d)     Multicellular organisms often have complex structures, such as lungs, for gas exchange.
Explain why single-celled organisms, like algae, do not need complex structures for gas exchange.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(3)
(Total 11 marks)
Q3.
(a)      Complete the equation for photosynthesis.
  light
energy
____________ + ____________  ____________ + oxygen
(2)
(b)     Scientists investigated how temperature affects the rate of photosynthesis.
The scientists grew some orange trees in a greenhouse.
They used discs cut from the leaves of the young orange trees.
The scientists used the rate of oxygen production by the leaf discs to show the rate of photosynthesis.
(i)      The leaf discs did not produce any oxygen in the dark.
Why?
______________________________________________________________
______________________________________________________________
(1)
(ii)     The leaf discs took in oxygen in the dark.
Explain why.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
(2)
(c)     In their investigation, the scientists measured the rate of oxygen release by the leaf discs in the light. The scientists then measured the rate of oxygen uptake by the leaf discs in the dark.
The graph shows the effect of temperature on
•   oxygen production in the light
•   oxygen production in the light added to oxygen uptake in the dark.
 
Use the information from the graph to answer each of the following questions.
(i)      Describe the effect of temperature on oxygen production in the light.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
(2)
(ii)     Explain the effect of temperature on oxygen production in the light when the temperature is increased:
from 25 °C to 35 °C
______________________________________________________________
______________________________________________________________
______________________________________________________________
from 40 °C to 50 °C.
______________________________________________________________
______________________________________________________________
______________________________________________________________
(2)
(d)     A farmer in the UK wants to grow orange trees in a greenhouse. He wants to sell the oranges he produces at a local market.
He decides to heat the greenhouse to 35 °C.
Explain why he should not heat the greenhouse to a temperature higher than 35 °C.
Use information from the graph in your answer.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(3)
(Total 12 marks)

Mark schemes
Q1.
(a)     (i)      LHS = water
accept H2O
do not accept H2O / H2O
1
RHS = oxygen
accept O2
do not accept O / O2 / O2
1
(ii)     light / sunlight
ignore solar / sun / sunshine
do not allow thermal / heat
1
(iii)    chloroplasts
allow chlorophyll
1
(b)     (i)      20
1
(ii)     any one from:
•        light (intensity)
•        temperature.
1
(c)     (i)      To increase the rate of growth of the tomato plants
1
(ii)     Because it would cost more money than using 0.08%
1
Because it would not increase the rate of photosynthesis of the tomato plants any further
1
[9]
Q2.
(a)     (i)      chloroplast
1
(ii)     cell wall
1
(b)     (i)      osmosis
accept diffusion
1
(ii)     cell wall (prevents bursting)
1
(c)     (i)      carbon dioxide
allow correct formula
1
glucose
allow sugar / starch
1
(ii)     any two from:
•        light sensitive spot detects light
•        tells flagellum to move towards light
•        more light = more photosynthesis
2
(d)     (cell has) larger SA:volume ratio
1
short (diffusion) distance
allow correct description
1
(diffusion) via cell membrane is sufficient / good enough
or
flow of water maintains concentration gradient
1
[11]
Q3.
(a)     LHS: carbon dioxide AND water
in either order
accept CO2 and H2O
allow CO2 and H2O
if names given ignore symbols
do not accept CO2 / H2O / Co / CO
ignore balancing
1
RHS: sugar(s) / glucose / starch / carbohydrate(s)
accept C6H12O6
allow C6H12O6
do not accept C6H12O6
1
(b)     (i)      light is needed for photosynthesis
or
no photosynthesis occurred (so no oxygen produced)
1
(ii)     oxygen is needed / used for (aerobic) respiration
full statement
respiration occurs or oxygen is needed for anaerobic respiration gains 1 mark
2
(c)     (i)      (with increasing temperature) rise then fall in rate
1
use of figures, ie
max. production at 40 °C
or maximum rate of 37.5 to 38
1
(ii)     25 – 35 °C
either  faster movement of particles / molecules / more collisions 
or particles have more energy / enzymes have more energy
1
or temperature is a limiting factor over this range
40 – 50 °C
denaturation of proteins / enzymes
ignore denaturation of cells
ignore stomata
1
(d)     above 35 °C (to 40 °C) – little increase in rate
or > 40 °C – causes decrease in rate
1
so waste of money or less profit / expensive
1
because respiration rate is higher at > 35 °C
or
respiration reduces the effect of photosynthesis
1
[12]