Practical Skills (OCR Gateway GCSE Biology)

Exam Questions

3 hours35 questions
1a
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2 marks

The fat in milk is broken down by the enzyme lipase.
A group of students investigate the effect of temperature on this breakdown of fat.

In their investigation they use an indicator called phenolphthalein.
Phenolphthalein is pink in alkali conditions but colourless in pH values below 8.

Step 1 One student puts 5 drops of phenolphthalein and 5 ml of full fat milk into a test tube.
Step 2 She adds 1 ml of lipase and stirs the mixture.
Step 3 She measures the time for the pink indicator colour to disappear.


The other students repeat these three steps but at different temperatures.
q16-paper1h-spec2018-ocrgcsebio
Table 16.1 shows the results of the group.

Temperature
(°C)
Time for pink colour
to disappear (s)
20 480
40 240
60 270
80 960


                                  Table 16.1

The pH falls as the fat in milk breaks down.

Explain why.

1b
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5 marks

Plot a graph of the results from Table 16.1 and draw a line of best fit.

q16b-paper1h-spec2018-ocrgcsebio

1c
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3 marks

Explain why the results at 20 °C and 40 °C are different.

1d
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3 marks

Explain why the results at 40 °C and 80 °C are different.

1e
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3 marks
(i)
One student says that the results show that the optimum temperature for the lipase is 40°C.

The teacher says that she cannot say for certain that it is 40°C.

Explain why

 [1]

(ii)
Give two modifications that the students could make to their method to find a more accurate value for the optimum temperature.
[2]
1f
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2 marks

The students rounded each time they measured to the nearest 10 seconds.

They rounded the times because they found it difficult to judge exactly when the pink colour had disappeared.

Describe and explain two ways the method could be improved to give a more accurate measurement.

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2a
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3 marks

A student investigates how light intensity affects the rate of photosynthesis in pondweed.

The diagram shows how he sets up his investigation.

q17-paper1h-spec2018-ocrgcsebio

  • He places the lamp at distances of 10, 30, 50, 70 and 90 cm from the beaker.
  • At each distance, he measures how much gas is given off from the pondweed in 1 minute.
(i)
The student counts the number of bubbles to get a measure of the amount of gas given off in photosynthesis.

Why is counting bubbles not an accurate way of measuring the amount of gas given off?
 [2]

(ii)
The student’s teacher says that collecting the gas, for example in a gas syringe, would give a more accurate measurement.

Explain why.
 [1]
2b
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4 marks
(i)
Sketch a line on the axes below to show the results you would expect.q17bi-paper1h-spec2018-ocrgcsebio

[2]

(ii)
Explain the shape of the graph. Two explanations are required.
 [2]
2c
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5 marks
(i)
Describe how and where oxygen is produced in photosynthesis.
[3]

(ii)
Explain why the amount of oxygen gas given off is not a true measure of the rate of photosynthesis.
[2]

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3a
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2 marks

A student wants to investigate the effect of air movement on transpiration.

The diagram shows how she sets up her experiment.q18-paper1h-spec2018-ocrgcsebio

1. She measures the rate of transpiration by measuring the loss in mass over 3 hours.
2. She does this first with the fan switched off.
3. She repeats this but with the fan switched on.
4. She keeps all other environmental conditions the same.


These are her results.

  Fan switched off Fan switched on
Mass loss in 3 hour (g) 37 144

Explain the difference in her results.

3b
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3 marks

The student kept environmental conditions like light intensity and temperature the same.

(i)
Why was it important to keep the light intensity the same?
[2]

(ii)
Why was it important to keep the temperature the same?
 [1]

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4a
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2 marks

A student investigates how different concentrations of sucrose solutions affect potatoes.

  • Three chips are cut from a potato.
  • Each chip is 5.0 cm long.
  • Each chip is left in a different concentration of sucrose solution for two hours.q20-paper1h-spec2018-ocrgcsebio

These are the results.

Concentration of
sucrose solution
Length of potato chip
Start
(cm)
After two hours
(cm)
1.0 M 5.0 4.5
0.5 M 5.0 5.0
0.0 M 5.0 5.5

Explain why the length of the chip increases in the 0.0 M solution.

4b
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2 marks

Explain why the length of the chip stays the same in the 0.5 M solution.

4c
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3 marks
(i)
Calculate the percentage change in the length of the chip in the 1.0 M solution.

Answer = ........................................ % [2]

(ii)
In experiments like this, what is the advantage of calculating percentage change, rather than just the actual change
[1]
4d
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2 marks
(i)
Measuring the length of the chips is a quick and easy way to get results.
However, it does not measure the total change to the chips.

Explain why.
 [1]

(ii)
What could the students measure to see the total change to the chips?
[1]

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5
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7 marks

Some students investigate how the rate of diffusion in animal cells is affected by the surface area : volume ratio.

1. They use three different sized gelatine cubes stained blue with pH indicator.
2. They put the cubes into a beaker of hydrochloric acid.
3. They measure the time for each cube to completely change colour.

q22-paper1h-spec2018-ocrgcsebio
The table shows their results.

Length of one side of
cube (cm)
surface area : volume
ratio
Time to completely
change colour
(seconds)
1 ............. 132
2 3:1 328
3 2:1 673


(a)

(i)
Calculate the surface area : volume ratio for the cube with sides of 1 cm.

answer = ........................................ [1]

(ii)
Calculate the rate of colour change for each of the three cubes.
  • Write your answers in the table below.
  • Show your answers in standard form.

    Length of one side of cube
    (cm)

    Rate of colour change
    (s–1)

    1 ........................................
    2 ........................................
    3 ........................................

[2]

(iii)
Use the results and your calculations in parts (i) and (ii).

Explain why most large multi-cellular organisms need transport systems, such as the blood system, but most single celled organisms do not.
 [2]

(iv)
Explain why using gelatine spheres instead of cubes might be more biologically accurate but suggest why the students used cubes instead.
 [2]

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6a
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2 marks

Students investigate how to extract DNA from peas.

Stage 1:

  • Chill 10cm3 of ethanol. Keep it on ice throughout the method for use in stage 2.
  • Make a thick ‘soup’ by blending 100cm3 of peas with salt and cold water. Blend for 15 seconds in an electric blender.
  • Strain the ‘soup’ through a mesh strainer and collect the liquid part in a beaker.
  • Add 30cm3 of washing-up liquid and swirl to mix.
  • Let the mixture settle for 5–10 minutes in a water bath at 60°C.

One group of students made a water bath using a beaker of water, thermometer and Bunsen burner. Another group used an electric water bath.

Write down two advantages of using an electric water bath.

1 ........................................
2 .........................................

6b
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2 marks

Low temperatures protect DNA by slowing down the activity of enzymes that destroy DNA. High temperatures break down membranes in the cell.

To extract DNA, some methods use a water bath at 60°C but other methods do not use an increased temperature.

Suggest two reasons for the different methods.

6c
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2 marks

Stage 2 isolates the DNA.

q16b-paper1h-june2018-ocrgcsebio

  • Pour the mixture collected from stage 1 into a test tube until a third full. Add protease enzymes to the test tube.
  • Slowly pour cold ethanol at an angle of 45° into the tube. Ethanol will float on top.
  • DNA is soluble in water, but salted DNA does not dissolve in ethanol and will form white clumps where the water and ethanol layers meet.
  • Twirl a glass rod and the DNA will collect on the rod.
  • Dry the sample on a pre-weighed filter paper and measure the mass of product.

Suggest two safety precautions which should be taken at stage 2.

Explain why each safety precaution is needed.

1 Safety precaution: ......................................
Explanation: ......................................................

2 Safety precaution: ........................................
Explanation: ........................................................

6d
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4 marks

Look at the table. It shows the results from the two groups of students in the investigation.

Type of water bath used Mass of DNA collected (mg)
Test 1 Test 2 Test 3 Mean
Beaker of water and Bunsen burner       22.9
Electric 33.6 32.3 33.3 ....................

(i)
Calculate the mean mass collected in the investigation using the electric water bath.

Give your answer to 1 decimal place.

Answer = ..................................... mg [2]

(ii)
The range of the three test readings for the beaker of water and Bunsen burner was 3.4.

Does the evidence support using an electric water bath instead of a beaker of water and Bunsen burner?

Explain your answer.

[2]

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7a
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2 marks

A student prepares onion cell slides to view under a microscope.

Put the stages in the correct order by writing the numbers 1 to 5 in the boxes.

   add a drop of iodine solution
   cut the onion into pieces
   peel off a thin layer of onion tissue
   put on a cover slip
   put the onion tissue on a slide

7b
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2 marks

Explain why the iodine solution is used.

7c
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4 marks

Look at the image of some onion cells.q16c-paper1f-spec2018-ocrgcsebio

(i)
Explain how the contents of the nucleus allow it to carry out its function.
[2]
(ii)
Explain why there are no chloroplasts in these onion cells.

[2]

7d
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2 marks

The diagram shows a layer of onion cells.q16d-paper1f-spec2018-ocrgcsebio
The actual length of the layer is 1.5 mm.

Calculate the average length of one onion cell.

Answer = ........................ mm

7e
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2 marks

A student thinks that using the highest magnification of a microscope is always best.

Explain why this may not be true.

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8a
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2 marks

A student wants to compare the transpiration rates of two plants.

The plants have different sized leaves.

Fig. 18.1 shows how she sets up her experiment.

q18a-paper1f-spec2018-ocrgcsebio

Fig 18.1

Suggest why the student put a layer of oil on top of the water.

8b
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3 marks

The student makes sure that each plant has the same number of leaves

Which other experimental conditions should she keep the same?

8c
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6 marks

The table shows the results of the experiment shown in Fig. 18.1.

  Plant A
(bigger leaves)
Plant B
(smaller leaves)
Mass at start (g) 261 273
Mass after 24 hours (g) 228 231


Write a conclusion with an explanation about this experiment.

Use the results and calculations in your answer.

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9a
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2 marks

A student investigates how light intensity affects the rate of photosynthesis in pondweed.

The diagram shows how he sets up his investigation.

q20-paper1f-spec2018-ocrgcsebio

He plans to place the lamp at distances of 10 cm, 15 cm and 20 cm from the beaker.

He plans to measure how much gas is given off from the pondweed in 10 seconds.

His teacher says he could improve his plan.

Write down two improvements he could make to his plan.

9b
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2 marks
(b)
The student counts the number of bubbles to get a measure of the amount of gas given off in photosynthesis.

Give two reasons why counting bubbles is not an accurate way of measuring the amount of gas given off.

[2]

9c
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1 mark

What is the gas given off in photosynthesis?

9d
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2 marks

Explain why the amount of this gas given off is not a true measure of the rate of photosynthesis.

9e
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4 marks
(i)
Sketch a line on the axes below to show the results you would expect.

q20ei-paper1f-spec2018-ocrgcsebio

[2]

(ii)
Explain the shape of the graph. Two explanations are required.

[2]

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10a
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5 marks

A student investigates the plants growing underneath a tree.

q17-paper2h-june2018-ocrgcsebio

He lays out a tape measure on the ground, starting at the tree. He then places a quadrat on the ground.

He measures the percentage of the ground in the quadrat that is covered by plants. He repeats this every metre away from the tree.

The table shows his results.

Distance from the tree
(m)
Percentage of ground covered
by plants (%)
1 10
2 15
3 18
4 22
5 50
6 58
7 62
8 64

Plot a graph of the student’s results and draw a line of best fit.

q17a-paper2h-june2018-ocrgcsebio
10b
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4 marks

The student thinks that shade from the tree is affecting the plants.

Explain how the student’s results show this.

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11a
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2 marks

Erythromycin is an antibiotic drug.

What is an antibiotic?

11b
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3 marks

It is important to get the dose of erythromycin right.

Too much erythromycin can be harmful.
However, recently some strains of bacteria have developed resistance to low concentrations of erythromycin.
To see how effective erythromycin is, it is tested using bacteria grown on agar plates.

This method is used:

  • A petri dish is used that has the bacteria growing evenly over the surface.
  • A disc of filter paper is soaked in erythromycin.
  • The disc is placed on the agar in the centre of the petri dish using sterile forceps.
  • The dish is incubated at 37°C.
(i)
Why did the scientists incubate the dish at 37°C rather than at higher or lower temperature?
 [2]
(ii)
Why is the filter paper disc moved using sterile forceps?
 [1]
11c
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5 marks
(i)
The diagram shows the actual size of the dish after incubation.specimen-paper-4-q18-q

This table is used to analyse the results of the experiment.

Area clear of bacteria including
the area of the disc
in mm2

Level of resistance
less than 133 resistant
133 to 416 intermediate resistance
more than 416 not resistant


Use the results of the experiment and the table to judge the level of resistance in this strain of bacteria. A ruler has been added to assist with accurate measurements (The area of a circle = π r2 and π = 3.14.)

answer= ....................................... mm2[3]

(ii)
Suggest any limitations to measuring the level of resistance with this method.
[2]

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12a
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1 mark

Student A and student B study the plants growing on a salt marsh.

They both sample the plants present by laying out two tape measures at right angles across the salt marsh.

They then place a square frame on the ground in different places and count the number of plants in the square, as shown below.q19b-paper2f-june2019-ocrgcsebio

What is the name of the square frame that they use to sample the plants?

12b
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8 marks

The diagrams show the position of each student’s samples across the salt marsh.
Each small square in the diagrams represents one sample.q19c-paper2f-june2019-ocrgcsebio

(i)
The whole salt marsh has an area of 2500m2.

Each square frame has an area of 0.25m2.

Calculate the percentage of the whole salt marsh that was sampled by student A.

Percentage = ................................ % [3]

(ii)
Look at the two students’ sampling shown in the diagrams.

Explain which student is likely to get the most accurate estimate for the number of plants in the salt marsh.

student ...................................
explanation ...........................
[3]
(iii)
Their teacher said that they should take care as there may be harmful bacteria in the salt marsh.

State two things that the students could do to reduce the risk of infection from the harmful bacteria.

1 ....................................
2 ....................................
[2]

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13
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7 marks

A student investigates the plants growing on a salt marsh. He uses a quadrat to sample the plants.

He puts down two long tape measures at right angles to each other across the salt marsh. He then picks numbers at random and uses them to decide where to place a quadrat.

The diagram shows the position of all his quadrats across the salt marsh.q22b-paper2h-june2019-ocrgcsebio

(i)
The salt marsh measured 50m × 50m.

Each quadrat measured 0.5m × 0.5m.

Calculate the percentage of the whole salt marsh that was sampled by the student.

Percentage = ............................... % [3]

(ii)
A second student sampled by placing five quadrats close together in the centre of the salt marsh.

Evaluate the sampling method of the second student compared to the method of the first student.
 [3]

(iii)
Suggest one factor that the students should consider in a risk assessment for their experiment.
 [1]

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14a
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4 marks

Scientists investigate antibiotic pollution in two different lakes.

They collect samples of water from the two lakes. The scientists then use aseptic techniques to investigate how resistant the bacteria in the water are to antibiotics.
Fig. 16.2 shows the apparatus they use.

fig-16-2-paper2h-nov2020-ocrgcsebio

Fig. 16.2


Describe how the scientists could use this apparatus to measure how resistant the bacteria are to antibiotics.

14b
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2 marks

The scientists also counted how many species of bacteria were resistant to antibiotics and how many species of bacteria were killed by antibiotics.

The scientists found these results.

  Number of different species of bacteria
In Lake Bellandur In Lake Jakkur
Resistant to antibiotics 53 35
Killed by antibiotics 28 37


Which lake has the highest levels of antibiotic pollution?

Tick () one box.
q16d-paper2f-nov2020-ocrgcsebio




Explain your answer.

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15
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8 marks

Some students decide to use lichens to try and work out how polluted their school grounds are.

They read about a scale called the Lichen Diversity Value (LDV).

It is worked out in this way:

  • choose four trees in the area
  • hold a quadrat on the north side of the trunk of one tree
  • count the total number of all the lichens in the quadrat
  • then do this on the east, south and west side of the tree
  • repeat this for each tree.
(i)
Suggest how the students could choose four trees.
 [1]
(ii)
The students put their results into a table.

  Number of individual lichens found in each quadrat
Tree number North East South West
1 3 11 18 7
2 4 12 17 8
3 5 10 15 12
4 4 15 12 9
mean 4.0 12.0 15.5  

The LDV is found by adding together the four mean values.

The students calculate the mean number of lichens on the north, east and south sides of the trees.

Calculate the mean for the west side and use this to calculate the LDV.

LDV = .............................. [2]

(iii)
This scale shows the diversity of the lichens shown by the LDV.q16diii-paper2h-spec2018-ocrgcsebio
What does the LDV show about the diversity of lichens in the school grounds?
 [2]
(iv)
LDV is calculated by counting all the lichens present.

What else about the lichens could the students look for to make a better assessment of pollution?
 [3]

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16a
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7 marks

The diagram shows a simple potometer.

The apparatus can be used to investigate the effect of light intensity on transpiration rates.

q19-paper1h-nov2020-ocrgcsebio

(i)
Describe what happens during transpiration.

[2]

(ii)
Describe how the apparatus can be used to investigate the effect of light on transpiration rates.

[3]

(iii)
The heat sink is a transparent tube of cold water.

Explain why a heat sink is used in this experiment.

[2]

16b
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8 marks

The table shows the results from using the potometer.

Distance of potometer
from the light (cm)
Distance gas bubble moved in one minute (mm)
Trial 1 Trial 2 Trial 3
10 70 74 72
20 73 75 71
30 52 49 51
40 42 30 31
50 12 14 13



(i)
The mean distance the gas bubble moved along the tube at 10cm from the light was 72mm.

The diameter of the narrow tube was 1mm.

Calculate the volume of water taken up by the plant.

Use the equation: volume = πr2l
where r is the radius of the tube and l is the distance the bubble moves
π = 3.14

Give your answer to 2 significant figures.

Volume of water = ................. mm3 /minute [3]

(ii)
Identify the anomalous reading in their recorded results and suggest a possible reason for this.
[2]

(iii)
How should the scientists deal with this anomalous reading when they process the data?
[1]

(iv)
The scientists described their results for 20cm as 73 ± 2.
Explain why they did this.
[2]

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17a
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3 marks

An experiment is set up to investigate how substances move into and out of cells.

Look at the results.q18a-paper1h-june2019-ocrgcsebio

Explain the results of this experiment.
Use ideas about molecules in your answer.

17b
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3 marks

Plant cells are also affected by osmotic conditions.

Look at the graph. It shows the percentage change in mass of potato chips in different concentrations of sucrose.q18c-paper1h-june2019-ocrgcsebio

(i)
Draw a curve of best-fit on the graph.
[1]

(ii)
Use the graph to estimate the concentration of sucrose that has the same water potential as the potato cells.

Concentration = .......................................... mol/dm3 [1]

(iii)
In a different experiment a sucrose concentration of 0.0mol/dm3 increases the mass of a carrot chip by 30%.

The carrot chip shows a 10% decrease in mass compared with its original mass for every 0.2mol/dm3 increase in sucrose concentration.

Calculate the x-axis intercept for the carrot chip.

x-axis intercept = ......................... mol/dm3 of sucrose [1]

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18a
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3 marks

Stomata are found on the surface of leaves.

The diagram shows some of the surface cells of a leaf.

q17-paper1f-june2018-ocrgcsebio
(i)
Write down the name of the cell labelled X.
[1]
(ii)
Describe two functions of stomata.
[2]
18b
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3 marks

Look at the diagram showing a plant cell.


q17b-paper1f-june2018-ocrgcsebio

(i)
The diameter of the nucleus in the diagram is 10 millimetres. The actual size of the nucleus is 10 micrometres.

Calculate the magnification of the diagram.

Answer = ....................................... × [2]

(ii)
Look at the picture of part of a plant cell.

q17bii-paper1f-june2018-ocrgcsebio

Use the arrow (measuring 75 mm) on the picture and the scale (measuring 15 mm) to estimate the length of the chloroplast.

Answer = ....................................... μm [1]

18c
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3 marks

Photosynthesis takes place inside chloroplasts.

(i)
Complete the chemical equation for photosynthesis.

6CO2 + .......................... → C6H12O6 + ........................
[2]
(ii)
Energy is taken in from the surroundings for photosynthesis to take place.

What name is used to describe reactions that take in energy?
[1]
18d
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3 marks

The graph is from an experiment to show the effect of temperature on the rate of photosynthesis.

q17d-paper1f-june2018-ocrgcsebio

(i)
What is the optimum temperature for photosynthesis in this experiment?
[1]
(ii)
The rate of photosynthesis was recorded in 5°C intervals.

The experiment could be improved to get a more precise value for the optimum temperature.

Explain how.
[2]

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