1.
(c)
(i)
(ii)
Carbon dioxide is being studied.
(1)
Sodium hydroxide solution is to absorb carbon dioxide from incoming
air.
(2)
Lime water is used to show that incoming air is free of carbon dioxide.
1
1
1
1
1
(iii)
The plant should be destarched but putting in the dark for 48 hours.
This is to ensure that starch detected subsequently is formed during the
experiment.
(iv)
Boil the leaf in hot water for 30 seconds.
Boil the leaf in alcohol.
Wash the leaf with warm water.
1
1
1
Add iodine solution to the leaf.
1
(v)
The control can be set up using the same apparatus but replacing the
1
concentrated sodium hydroxide solution and lime water with water.
(Total: 10 marks)
3.
(a)
(i)
C - *spongy mesophyll / cells / layer
D - *guard cell
cells are closely packed
possessing a larger number of chloroplasts
1
1
1
1
(iv)
for rapid diffusion of gases to facilitate photosynthesis / inflow of carbon
dioxide / outflow of oxygen
(1) air in the intercellular spaces expands on heating
and passes out through the stomata
(2) stomata occur on only one surface of the leaf
1
1
1
1
(v)
A (cuticle)
there is no danger of desiccation
1+1
cell D (guard cell)
gaseous diffusion occurs all over the plant surfaces
where there is no cuticle
1+1
(ii)
(iii)
[accept other suitable answers]
(Total: 12 marks)
1.
(a)
(i)
(ii)
(iii)
(iv)
(v)
1
1
1
Graph: correct choice of axes with labels (all or none)
correct plotting of points
joining up of all points
Rate
Rate:
Reasons
1, 1
1, 1
Adding sodium/potassium hydrogen carbonate solution (NaHCO3/KHCO3)
To kill the microorganisms
that would respire and give out carbon dioxide/consume oxygen
Only green light can pass through and reach the plant
green light is not suitable for photosynthesis OR chlorophyll only absorbs blue
and red light
light growth is because of no photosynthesis for producing food
leaves turn yellow because the degenerated chlorophyll is not replaced
1
1
1
1
(1)
increases rapidly
carbon dioxide is the raw material for
photosynthesis
(2)
increases slowly
some other factors become limiting
1
1
1
(Total: 14 marks)
1.
(b) b82-1-1b.doc
(i)
Graph – correct label for either or both axes/correct choice of axis
correct plotting of any 5 points
joining the points to form a smooth curve
1
1
1
(ii) Gas production decreases as distance increases
owing to reduction in light intensity
with less energy for photosynthesis (or vice versa)
(iii) 2.16 or 10.8÷5 (allow ± 0.2 or 1/5)
mm/min
(accept 10.8 mm/5 min)
(iv) *oxygen/O2
(v) Rate of photosynthesis (or oxygen production ) is less than/equal to rate of respiration
(oxygen consumption)
(vi) To avoid the effect of heat produced from the lamp when it is too close
as factors other than light should be kept constant.
1
1
1
1
1
1
1
1
1
(Total: 12 marks)