Q1.
This question is about photosynthesis.
(a) What is the symbol equation for photosynthesis?
Tick (✓) one box.
6 CO2 + C6H12O6 → 6 H 2O + 6 O 2
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
6 CO2 + 6 H2O → C6H12O6 + 6 O2
6 O 2 + 6 H 2O → 6 CO2 + C6H12O6
(1)
A student investigated the relationship between temperature and the rate of
photosynthesis.
The student measured the volume of gas produced by an aquatic plant in 1 hour.
The student collected the gas in a measuring cylinder.
The table below shows the results.
Volume of gas produced
Temperature in °C
in 1 hour in cm3
10 1
15 2
20 4
25 8
30 16
35 16
40 2
45 0
(b) Describe the effect of increasing temperature on the rate of photosynthesis.
Use data from the table above.
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(3)
(c) Explain why no gas was produced by the plant at 45 °C.
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(2)
(d) How could the student increase the accuracy of the results?
Tick (✓) one box.
Repeat the investigation, collecting the gas for 24 hours.
Repeat the investigation, measuring the volume of gas to 0.5 cm3.
Repeat the investigation using a different aquatic plant.
Repeat the investigation, using temperatures of 5 °C and 50 °C.
(1)
A person grows tomatoes in a greenhouse.
(e) The mean temperature of the greenhouse is 15 °C.
A heater would keep the temperature of the greenhouse at 25 °C.
Suggest two reasons against using a heater set at 25 °C in the greenhouse.
Do not refer to cost in your answer.
1 _________________________________________________________________
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2 _________________________________________________________________
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(2)
(f) The person cut a stem from one of the tomato plants.
The cut stem was placed in soil to grow new roots.
Which tissue in the cut stem will differentiate into new root cells?
Tick (✓) one box.
Epidermis
Meristem
Mesophyll
Phloem
(1)
(Total 10 marks)
Q2.
Light intensity varies during 24 hours.
The figure below shows the overall exchange of carbon dioxide and oxygen for a tree at
three different light intensities.
Explain the overall exchange of carbon dioxide and oxygen at the three different light
intensities.
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(Total 6 marks)
Q3.
Photosynthesis is an important chemical reaction in plants.
(a) Why is light needed for photosynthesis?
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(1)
(b) What is the equation for photosynthesis?
Tick (✓) one box.
C6H12O6 + CO2 → 6 O2 + 6 H2O
CO2 + H2O → CH2O + O2
6 CO2 + 6 H2O → C6H12O6 + 6 O2
6 O2 + 6 H2O → C6H12O6 + 6 CO2
(1)
(c) A student investigated the effect of different colours of light on the rate of
photosynthesis at room temperature.
The student used pondweed in water.
A piece of pondweed was placed in red light, then in blue light and then in green
light.
Each colour of light was the same intensity.
Describe how the student should make accurate measurements to obtain valid
results for the rate of photosynthesis.
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(4)
A scientist investigated the effect of different wavelengths of light on the rate of
photosynthesis.
The wavelength of light determines the colour of the light.
Figure 1 shows the student’s results.
Figure 2 shows the scientist’s results.
Figure 1
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Figure 2
(d) Why are the results for the two investigations presented differently?
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(2)
(e) Suggest the range in wavelength of green light.
Use Figure 1 and Figure 2.
Range in wavelength of green light = from _______ nm to _______ nm
(1)
(Total 9 marks)
Q4.
(a) Respiration is a process which takes place in living cells. What is the purpose of
respiration?
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(1)
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(b) (i) Balance the equation for the process of respiration when oxygen is available.
C6H12O6 + O2 → CO2 + H2 O
(1)
(ii) What is the name of the substance in the equation with the formula C 6H12O6?
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(1)
(c) Oxygen is absorbed through the alveoli in the lungs.
(i) How are the alveoli adapted for this function?
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(2)
(ii) Name the gas which is excreted through the alveoli.
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(1)
(d) (i) What is the name of the process of respiration when oxygen is not available?
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(1)
(ii) Describe the process of respiration which takes place in human beings when
oxygen is not available and give an effect.
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(3)
(Total 10 marks)
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Mark schemes
Q1.
(a) 6CO2 + 6H2O → C6H12O6 + 6O2
1
(b) (as temperature increases) the rate of photosynthesis increases then
(the rate of photosynthesis) decreases
ignore references to volume unqualified
1
fastest rate between 30 °C and 35 °C
allow a fastest rate at a temperature above 30 °C and below
35 °C
allow reaches an optimum temperature between 30 °C and
35 °C
1
up to 30 °C the rate doubles every 5 °C increase
allow up to 30 °C the rate increases at an increasing rate
allow up to 30 °C the rate increases exponentially
1
(c) enzymes (in the plant / chloroplast) become destroyed
allow enzymes become denatured
do not accept enzymes are killed
do not accept cells / plants are denatured
1
(because) active site changes shape
OR
the active site changes shape (1)
(so) the substrate no longer fits / binds (1)
OR
enzymes (in the plant / chloroplast) become destroyed (1)
allow enzymes become denatured
do not accept enzymes are killed
do not accept cells / plants are denatured
(so) the substrate no longer fits / binds (1)
ignore the plant is killed / dead
1
(d) repeat the investigation, measuring the volume of gas to 0.5 cm3
1
(e) any two from:
• may have too many tomatoes to eat / sell
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allow the idea of a glut or all ripen at the same time
• other factors could limit photosynthesis
allow other named limiting factor could limit photosynthesis
allow factors could limit tomato production
• the optimum temperature might be above / below 25 °C
• greenhouses are poorly insulated
• pollution from the heater
allow increase carbon dioxide emissions
allow increase global warming
• increase the rate of transpiration
allow increase the water loss from the plant
• increased spread of plant disease(s)
if no other mark awarded allow it is a fire hazard for 1 mark
2
(f) meristem
1
[10]
Q2.
Level 3: Relevant points (reasons/causes) are identified, given in detail and logically
linked to form a clear account.
5-6
Level 2: Relevant points (reasons/causes) are identified, and there are attempts at
logical linking. The resulting account is not fully clear.
3-4
Level 1: Points are identified and stated simply, but their relevance is not clear and
there is no attempt at logical linking.
1-2
No relevant content
0
Indicative content
Bright light:
• rate of photosynthesis is high due to high light intensity
• (extra) carbon dioxide is absorbed from the air
• (so) oxygen is released into the air
• carbon dioxide produced in respiration is used for photosynthesis
• (so) no carbon dioxide released from plant or into the air
• sufficient oxygen for respiration is produced by photosynthesis
• (so) no extra oxygen absorbed from the air
• rate of photosynthesis is greater than rate of respiration
Dim light:
• no net / overall flow / exchange of carbon dioxide or oxygen with the air
• (because) rate of respiration equals rate of photosynthesis
• carbon dioxide produced in respiration is used for photosynthesis
• no (extra) carbon dioxide is absorbed from the air
• oxygen produced by photosynthesis is used in respiration
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• no (extra) oxygen is absorbed from the air
No light:
• no photosynthesis occurs as no light
• (so) no carbon dioxide is absorbed and no oxygen released / produced
• plant respires so takes in oxygen and releases carbon dioxide into the air
General points:
• plants photosynthesise when there is light using carbon dioxide and producing
oxygen
• rate of photosynthesis depends on light intensity
• respiration occurs at all times of the day
• respiration uses oxygen and produces carbon dioxide
Level 3 response must include explanation at all three light intensities,
demonstrating a good understanding of both photosynthesis and respiration.
For Level 2 correct reference to both processes and to both gases
[6]
Q3.
(a) to transfer energy
allow idea that light is the source of energy (for the reaction)
do not accept to produce / make / create / use energy
or
photosynthesis is an endothermic reaction
1
(b) 6CO2 + 6H2O → C6H12O6 + 6O2
1
(c) allow the pondweed to equilibrate in the light
allow leave the pondweed in the light (for a few minutes)
before taking measurements
allow use the same concentration of sodium hydrogen
carbonate solution
ignore control carbon dioxide concentration unless method
described
ignore use same intensity / distance of light
ignore control temperature
ignore use same pondweed
1
use a gas syringe
or
use a (measuring) cylinder to measure / collect the oxygen / gas produced
do not accept carbon dioxide
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ignore references to counting bubbles
1
measure time oxygen / gas is collected for using a timer / stopwatch /
stopclock
1
repeat the measurements and calculate a mean
allow repeat the measurements (several) and discard
anomalies
1
(d) independent variable in student’s investigation is categoric / discrete
allow colour of light is a categoric / discrete variable
ignore discontinuous
1
independent variable in scientist’s investigation is continuous
allow wavelength is a continuous variable
1
ignore answers relating to the scale on the y-axis
(e) 492 to 577 (nm)
allow answers in range 475 to 525 and 575 to 650 (nm)
1
[9]
Q4.
(a) to transfer / provide / give release energy
or production of ATP / adenosine triphosphate (molecules)
accept to give heat
1
(b) (i) C6H12O6 + 6O2 → 6CO2 + 6H2O
accept any other
n : 6n : 6n : 6n ratio
do not credit if any other changes have been made
1
(ii) glucose
do not credit sugar / sucrose
1
(c) (i) any two from
large surface
thin (surface)
moist (surface)
(with a good) blood supply
2
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(ii) carbon dioxide
accept water vapour
do not credit just water
1
(d) (i) anaerobic (respiration)
1
(ii) any three from
in mitochondria
glucose decomposes / breaks down / reacts
or glucose → lactic acid for (2) marks
to give lactic acid
or breathing hard
or lactic acid → CO2 + water
causing pain
(leaving an) oxygen debt
(quick) source of energy
(but) less efficient than aerobic respiration
accept less efficient than with oxygen
3
[10]
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