GCSEBiologyOCR GatewayExam Questions2. Scaling Up2.1 Supplying the Cell

Supplying the Cell (OCR Gateway GCSE Biology)

Exam Questions

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2.1 Supplying the Cell

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2.1 Supplying the Cell

1a
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A scientist clones a cauliflower plant.
q18a-paper1f-june2019-ocrgcsebio

He uses small pieces of the cauliflower plant called explants.

This is the method the scientist uses to get the explants:

  • Place the equipment in a beaker of bleach and swab the bench with 70% alcohol.
  • Collect a small piece of cauliflower and place on a white tile.
  • Use a scalpel to cut the piece of cauliflower lengthways into small 3–5mm pieces called explants.
  • Measure the mass of the explants.
(i)
Suggest why the scientist uses a scalpel rather than a kitchen knife.
 [1]
(ii)
Write down one safety precaution that the scientist should take when using a scalpel.
[1]
(iii)
The explants are then prepared for cloning by placing on an agar jelly plate.

Agar jelly contains water, sugars and minerals.q18aiii-paper1f-june2019-ocrgcsebio
When the explants are placed on the agar jelly plate they have no roots or leaves.

Explain why the explants must be placed on the agar jelly plate.
 [2]

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1b
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To grow the explants, the scientist places the agar jelly plate in a warm room near to a window.

(i)
Explain why this will help the explants grow and develop into clones.
 [2]

(ii)
Using a heated cabinet with light bulbs inside the cabinet would improve this method.

Explain why.
 [2]
(iii)
The scientist examines the agar jelly plate regularly.

Growth of the explants is visible in the plate within 10 days and parts of the explants are turning green.q18biii-paper1f-june2019-ocrgcsebio

What conclusion can be made about why the explants have parts that are turning green?
 [1]

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1c
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The mass of the explants at the start was 15g.

After 10 days the mass of the explants was 28g.

Calculate the percentage increase in mass of the explants.

Give your answer to 1 decimal place.

Percentage increase = .................................... %

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1d
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The cells in cauliflower explants behave the same way as embryonic stem cells do in animals.

Explain why it is more difficult to clone adult animals than to clone cauliflower.

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2
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Oxygen enters red blood cells by diffusion.

Describe and explain how red blood cells are adapted for the efficient uptake and transport of oxygen.

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3a
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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.

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3b
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Sodium ions help regulate the balance of water between the blood and body cells.

In some people the level of sodium ions in the blood can become very low. This can alter the balance of water between the blood and body cells. Doctors can prescribe drugs for patients who have this condition.

Explain how low sodium ion levels in the blood will affect the cells of the body and suggest why drugs that block the action of ADH can treat this condition.

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3c
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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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3d
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Osmotic conditions can increase the size of plant tissue but stem cells are responsible for growth of new cells.

What name is given to plant tissue that contains stem cells?

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