Exam code: 4XSD1
The diagram shows part of the digestive system of a cow.
Name the parts labelled P and Q.
The cow’s stomach contains microorganisms that digest plant cell walls.
Suggest why these microorganisms are useful to a cow.
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The diagram shows a plant cell.
(i) Which part of this cell contains chlorophyll?
P
Q
R
S
(ii) Which of these is found in chlorophyll?
Calcium
Iron
Magnesium
Water
(iii) Describe the role of chlorophyll.
[2]
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The pancreas produces a range of enzymes involved in the digestion of food.
Explain the meaning of the term enzyme.
In which of the following locations does digestion by the enzyme amylase take place?
Mouth and pancreas
Mouth and stomach
Small intestine and pancreas
Mouth and small intestine
The diagram below shows an enzyme and an associated molecule labelled X that can bind with the enzyme at location Y.
Name molecule X and location Y.
The 'lock and key hypothesis' is often used as a model to describe the action of enzymes.
Use your knowledge of the lock and key hypothesis and the diagram in part (c) to explain how enzymes function in digestion.
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The graph below shows the effect of temperature on the rate of an enzyme-catalysed reaction.
Explain why the rate of an enzyme-catalysed reaction decreases after point B.
A scientist investigated how the digestive enzyme amylase breaks down starch into sugar maltose.
He added the enzyme to a solution of starch and measured the concentration of starch every 10 minutes.
The results are shown in the table below.
Time / min | Concentration of starch / mg cm -3 |
|---|---|
0 | 17.2 |
10 | 11.1 |
20 | 7.2 |
30 | 5.3 |
40 | 4.2 |
Rate of reaction can be calculated using the following equation:
Calculate the average rate of the reaction between 0 and 20 minutes.
Bile is a secretion that helps with digestion.
State one way in which bile aids digestion.
The diagram below shows the organs of the human digestive system.
(i) Bile is produced by organ X
Name organ X.
[1]
(ii) Identify the organ in which bile is stored after it is produced.
[1]
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A leaf contains various structures that enable it to carry out photosynthesis.
Draw lines to connect each listed structure with the corresponding adaptation.
Structure | Adaptation |
|---|---|
Waxy cuticle | Allows gas exchange to occur |
Stomata | Tightly packed with chloroplasts for maximum absorption of light |
Palisade mesophyll | Protect the leaf from water loss |
Spongy mesophyll | Increases the surface area to volume ratio for the diffusion of gases |
The diagram below shows a cross section through a leaf.
Structure Y represents a vascular bundle.
(i) Identify two types of tissue found in structure Y.
[2]
(ii) Describe the function of each type of tissue identified in part (i).
[2]
Layers X and Z in the diagram in part (b) form the outer boundaries of the leaf.
(i) Identify one visible difference between layer X and layer Z.
[1]
(ii) The cells in layer X are transparent.
Explain the importance of this to the plant.
[2]
Carbon dioxide concentration is one of several factors that can limit the rate at which photosynthesis occurs.
Sketch a graph that shows how carbon dioxide concentration affects the rate of photosynthesis. You should label your axes with carbon dioxide concentration on the X axis and the rate of photosynthesis on the Y axis.
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A student investigates the effect of light intensity on photosynthesis in leaf discs.
This is the student’s method.
Cut equal sized discs from a leaf
Remove the plunger from a 20 cm3 syringe and place a disc into the syringe
Replace the plunger in the syringe and fill the syringe with 2 % sodium hydrogen carbonate solution, which provides carbon dioxide
Place your thumb over the end of the syringe and pull the plunger back until the disc sinks
Position the syringe vertically
Place a lamp five centimetres from the syringe
Record the time taken for the leaf disc to rise to the top of the syringe
Repeat the experiment with the lamp at increasing distances from the syringe
The leaf discs rise in the solution due to the production of gas during photosynthesis.
The diagram shows some of the apparatus used.
Give the balanced chemical symbol equation for photosynthesis.
(i) State how the student could improve the reliability of their results.
[1]
(ii) Give the dependent variable in the investigation.
[1]
The graph shows the results of the investigation.
Explain the effect of increasing the distance of the lamp on the time taken for the leaf disc to rise to the top of the syringe.
Describe how the student could test the leaf discs for the presence of starch.
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A student investigates factors that affect photosynthesis.
In his first experiment, the student uses this method to investigate the effect of light on photosynthesis.
Place a plant in the dark for 24 hours
Cover part of leaf X with black paper
Place the plant in the light for 24 hours
The diagram shows the plant in the light.
Describe how the student tests leaf X to show the effect of light on photosynthesis.
In his second experiment, the student uses a water plant to investigate the effect of carbon dioxide concentration on the rate of photosynthesis.
He does the experiment at two different light intensities.
The table shows the student’s results.
Carbon dioxide concentration in arbitrary units | Rate of photosynthesis in bubbles per minute | |
|---|---|---|
low light intensity | high light intensity | |
0.00 | 0 | 0 |
0.02 | 20 | 20 |
0.04 | 29 | 35 |
0.06 | 35 | 47 |
0.08 | 39 | 68 |
0.10 | 42 | 84 |
0.12 | 45 | 89 |
0.14 | 46 | 90 |
0.16 | 46 | 90 |
0.18 | 46 | 90 |
(i) Explain the student’s results.
[4]
(ii) Describe how the student could change the light intensity in this investigation.
[1]
(iii) Give the dependent variable in this investigation.
[1]
(iv) Give one way in which the student could control the biotic variable in this investigation.
[1]
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The table gives the percentage composition by mass of human breast milk, and of cow’s milk.
Substance | Percentage by mass (%) | |
|---|---|---|
Breast milk | Cow's milk | |
Water | 87.0 | 88.0 |
Vitamins | Trace | Trace |
Fat | 3.8 | 5.0 |
Carbohydrate | 7.9 | 3.0 |
Minerals | 0.2 | 0.7 |
Protein | 1.0 | 3.3 |
Discuss whether cow’s milk is a suitable alternative to breast milk for young babies.
Use data from the table and your own knowledge to support your answer.
Human breast milk may contain insufficient vitamin D for a growing child.
Give two ways that additional vitamin D could be provided for the child.
Describe how a sample of cow’s milk could be tested for protein.
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The diagram shows part of the human digestive system.
Figure 1
In which of these parts is hydrochloric acid produced?
(ii) In which of the parts shown in Figure 1 are faeces stored?
The liver produces bile.
Explain the role of bile in digestion.
Some people have a condition called coeliac disease.
In this condition the body reacts to eating gluten, a protein found in wheat.
This reaction damages the villi in the small intestine.
The diagram shows how the villi in the small intestine are damaged.
(i) Explain how the undamaged villi are adapted for their function.
[4]
(ii) Explain why children with untreated coeliac disease may grow more slowly and become tired more easily than children without coeliac disease.
Use the information from the diagram and your own knowledge to support your answer.
[4]
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A teacher does an investigation to show that plants require carbon dioxide and light for photosynthesis.
This is the teacher’s method.
Place a potted plant in the dark for 24 hours
Place a strip of black paper over two of the plant’s leaves
Pour some sodium hydroxide solution into a flask
Insert one of the leaves into the flask
Seal the flask with a cotton wool plug
Place the plant in bright light for 12 hours
Remove the two leaves and safely test them for starch
This diagram shows the teacher’s apparatus.
(i) Explain why the potted plant is placed in the dark for 24 hours.
[2]
(ii) Explain one role of leaf Y in the investigation.
[2]
(iii) Describe how to test the leaves for starch safely.
[4]
Explain how the results of this investigation would show that light is required for photosynthesis.
Plants convert the glucose they produce into starch.
Explain why plants store carbohydrate as starch rather than as glucose.
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A student investigated the effect of different colours of light on the rate of photosynthesis in a water plant.
This is the student’s method.
Place a 1 % sodium hydrogen carbonate solution in a boiling tube
Cut a 5 cm length of pondweed and place it in the tube
Place a lamp 10 cm from the tube containing the pondweed
Leave the pondweed for 10 minutes until it starts to produce bubbles from the cut end
Count the bubbles produced in one minute
Count the bubbles for two more one minute periods
The student repeated the experiment three more times using filters in front of the lamp that let through either red light, blue light or green light.
These are the student’s results.
Colour of filter | Number of bubbles per minute | |||
|---|---|---|---|---|
Test 1 | Test 2 | Test 3 | Mean | |
No filter | 47 | 84 | 80 |
|
Red | 48 | 48 | 42 | 46 |
Blue | 55 | 56 | 50 | 54 |
Green | 9 | 8 | 10 | 9 |
Write the balanced symbol equation for photosynthesis.
(i) Anomalous results are not included in the calculation of the mean.
Calculate the mean number of bubbles per minute for the lamp with no filter.
[2]
(ii) Explain the student’s results.
[4]
(iii) Give two abiotic variables that the student should control in her experiment.
[2]
(i) Explain why measuring the rate of photosynthesis by counting bubbles may not be an accurate method to use.
[2]
(ii) Suggest an alternative method that the student could use to measure the rate of photosynthesis in her experiment.
[2]
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Describe how you could use hydrogen-carbonate indicator to investigate the effect of light intensity on net gas exchange in a leaf.
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A student does an experiment to show that a leaf is only able to produce starch if it receives enough light.
The student removes all the starch from the leaf before starting the experiment.
(i) Describe how the student could remove all the starch from the leaf.
[2]
(ii) State why the student removes all the starch from the leaf before starting the experiment.
[1]
Before testing a leaf for starch, chlorophyll needs to be removed.
Give a safety precaution the student needs to take when removing chlorophyll.
Give a suitable control the student should use in this experiment.
Describe how the structure of the leaf is adapted for photosynthesis.
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Explain how food passes down the oesophagus.
The diagram shows the human alimentary canal.
Which labelled structure produces bile?
A
B
C
D
Describe the role of bile in digestion.
Lipase inhibitors are chemicals that bind to lipase enzymes.
To test the effect of a lipase inhibitor, equal masses of full fat milk are placed into two test tubes.
Lipase inhibitor is added to one test tube.
Lipase is added to both test tubes and the pH of each solution is measured every five minutes.
The results are shown in the table.
Time in minutes | pH of solution | |
|---|---|---|
Without lipase inhibitor | With lipase inhibitor | |
0 | 8.0 | 8.0 |
5 | 7.6 | 7.8 |
10 | 7.2 | 7.8 |
15 | 6.3 | 7.7 |
20 | 5.8 | 7.5 |
(i) Calculate the mean rate of pH change per minute of the solution without lipase inhibitor.
[2]
(ii) Explain the difference in the changes of pH of the solutions in the two test tubes during the 20-minute period.
[2]
(iii) Doctors use this method to investigate the use of lipase inhibitor as a treatment for obesity.
Give three volunteers a tablet containing the lipase inhibitor
Give another three volunteers a tablet with no lipase inhibitor
Give all the volunteers 100 cm3 of olive oil to drink
Measure the lipid concentrations in the blood of the volunteers after three hours
Some of the volunteers reported abdominal pains three hours after drinking the olive oil.
The table shows the doctors’ results.
Tablet contents | Blood lipid concentration in mg per dm3 | Abdominal pains | |
|---|---|---|---|
At start | After 3 hours | ||
Inhibitor | 35 | 38 | Yes |
Inhibitor | 37 | 42 | No |
Inhibitor | 37 | 43 | Yes |
No inhibitor | 35 | 62 | No |
No inhibitor | 37 | 64 | No |
No inhibitor | 35 | 45 | Yes |
Discuss the use of the lipase inhibitor as a treatment for obesity.
Use the data from the table to support your answer.
[5]
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The diagram shows part of the gut of a rabbit.
The rabbit is a primary consumer and eats mainly grass and other vegetable material.
Name the parts labelled A, B, C and D.
The gut of a rabbit has a large caecum and appendix. These contain bacteria that are able to produce the enzyme cellulase.
Explain how these bacteria help the rabbits with their diet of plant material.
The human gut has a caecum and appendix but they are much smaller than those in the rabbit.
(i) Suggest why the human gut only has a small caecum and appendix.
[1]
(ii) In humans, the appendix also acts as a store of useful bacteria. Scientists have discovered that patients who have had their appendix removed are more likely to develop infections of the colon.
Explain how having no appendix may increase the likelihood of bacterial infections of the colon.
[2]
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A student investigated the digestion of bread by the enzyme amylase.
This is the method used.
add a piece of bread to a container
add amylase solution to the bread
leave for a few minutes
pour water on to the bread
filter the mixture using the apparatus shown in the diagram
test the solution from the digested bread with Benedict’s solution
Explain the result of the Benedict’s test if the amylase digests the starch in the bread.
The student’s method lacks detail.
Rewrite the method so that the student could make a valid conclusion about the effect of temperature on amylase.
The student predicted that the rate of digestion of starch would keep increasing as temperature increased.
Comment on this prediction.
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