Digestion & Absorption (AQA A Level Biology)

Exam Questions

2 hours15 questions
1a2 marks

Define the biological term, ‘absorption’.

1b1 mark

The liver and stomach are both major organs of the digestive system. State why the stomach is classified as part of the alimentary canal whereas the liver is not. 

1c3 marks

Use your knowledge of digestion to complete the boxes labelled K, L and M in Table 1. The first row has been completed for you as an example. 

Table 1

Molecule(s) Digestion product(s) Enzyme
starch maltose amylase
protein  K protease
L glycerol lipase
sucrose glucose and fructose M

1d2 marks

The salivary glands and the pancreas both act as glands in the process of digestion. State what is meant by the term, ‘gland’ in the context of digestion. 

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2a2 marks

Outline two physical changes that occur to food in the mouth as food is being prepared for swallowing and further digestion. 

2b3 marks

Name three conditions of the gastric (stomach) environment that enable chemical and physical digestion. 

2c1 mark

Figure 1 shows the primary structure of a protein ingested as part of a mammalian diet. 

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Indicate, on Figure 1, using a cross ( ) a position that would be cut by an exopeptidase enzyme.

2d2 marks

State the two main roles of bile in digestion.

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3a2 marks

In an experiment examining the rate of reaction of an amylase-catalysed reaction, state and explain the final colour that would be observed from the iodine test in a test tube containing denatured amylase. 

3b2 marks

In a different experiment to measure the effect of temperature on the rate of a lipase-catalysed reaction, lipids in the test sample are broken down to fatty acids and glycerol by the action of lipase. Explain why pH is a suitable dependent variable for this experiment and choose one suitable control variable.

3c1 mark

The catalytic activity of lipase takes place solely in the ___________. Name this organ of the digestive system. 

3d1 mark

Bile emulsifies fats. Explain what ‘emulsifies’ means. 

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4a1 mark

Name the substance that is also transported when glucose is absorbed. This substance is necessary for effective glucose absorption. 

4b2 marks

Identify the structures which are small projections, 0.5 to 1.0 mm long, of the epithelial lining of the small intestine. State their purpose. 

4c2 marks

Figure 1 shows a villus. 

Figure 1

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Identify structures X and Y and state the organ system to which each structure belongs.

4d1 mark

Name the process by which food is pushed along the oesophagus and small intestine.

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5a2 marks

Describe and explain one property of visking tubing (sometimes called dialysis tubing) that makes it a good choice for experiments that model the action of enzymes in the gut. 

5b2 marks

A ‘Model Gut’ experiment was set up as shown in Figure 1 and maintained at 37°C for 30 minutes. 

Figure 1

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Predict and explain the result of a starch (iodine) test on the solution outside the visking tubing (in the beaker) after 30 minutes. 

5c2 marks

The experiment shown in Figure 1 can be used to measure the effect of pH on amylase activity by setting up tests at various set pH values. Buffer solutions are used in these investigations. Define ‘buffer solutions’ and state their usefulness in such an investigation. 

5d1 mark

In the experiment shown in Figure 1, name a suitable biochemical test to demonstrate the presence of the products of starch digestion in the water surrounding the visking tubing after 30 minutes. 

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1a1 mark

Figure 1 below shows part of the human digestive system. The different organs are labelled H - M.

m-q1

Give the letter of the organ that temporarily stores faeces before egestion.

1b2 marks

Name organ L in Figure 1 and the digestive enzyme that it produces.

1c3 marks

The glucose concentration in blood rises after eating a meal that contains carbohydrates.

The increase in glucose concentration occurs at a slower rate if the carbohydrate ingested is starch, rather than sucrose. Explain why this is

1d3 marks

Glycaemic load (GL) is a measure of how much digestible carbohydrate a person diet contains. A higher GL diet will raise the blood glucose concentration more rapidly after a meal. A high GL diet can also cause the concentration of harmful lipids in the blood to increase.

Lab technicians decided to investigate the relationship between different glycaemic load diets and the risk of developing coronary heart disease (CHD), specifically in women.

The glycaemic loads of the diets of a large number of women were determined by technicians. The women were then divided into 5 groups. Group 1 had the lowest GL diets and group 5 had the highest GL diets. The technicians then determined the risk of developing CHD in each group of women.

Figure 2

m-q1-2

Use the information from the question and Figure 2 to describe and explain how the glycaemic load of a diet affects the risk of developing CHD.

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2a1 mark

Figure 1 below outlines the mechanism of lipid digestion and absorption.

Figure 1

m-q2

What type of cell is cell A?

2b3 marks

Figure 1 shows the formation of lipid droplet and micelles. Explain the advantages of these structures.

2c4 marks

Triglycerides are hydrolyzed by the enzyme lipase.

A student wanted to investigate the breakdown of triglycerides in cow milk by human lipase at 20 °C.

They recorded the pH of a sample of cow’s milk before and after adding human lipase. They used a pH meter to measure the pH. Their results are shown in figure 2.

Figure 2


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Describe and explain the changes in pH after human lipase is added.

2d2 marks

The student carried out his experiment at a controlled temperature of 20 °C. They repeated the experiment at 25 °C.

Draw a line on the graph (Figure 2) to show the results you would expect at 25 °C.

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3a2 marks

Figure 1 below shows the digestion pathway of proteins. 

Figure 1  

m-q3          

           

Name the missing molecule X and missing enzyme Y.

3b2 marks

Describe the different actions of endopeptidases and exopeptidases.

3c2 marks

Pancreatitis is a medical condition that can lead to the pancreatic duct becoming blocked. It can also cause protein-digesting enzymes to be released into the bloodstream. Suggest one reason why this might be harmful.

3d3 marks

Figure 2 below illustrates the co-transport mechanism for the absorption of amino acids into the blood by a cell lining in the small intestine.

Figure 2

m-q3-2

Use Figure 2 and your knowledge of the co-transport mechanism, to explain why epithelial cells in the small intestine contain a large number of mitochondria.

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4a5 marks

Describe the role that enzymes play in the digestion and complete breakdown of starch.

4b3 marks

A lab technician set up the experiment shown in Figure 1 below.

Figure 1

m-q4

After 20 minutes, the samples were taken from the liquid in the beaker, and from the liquid inside the Visking tubing. Biochemical tests were carried out on these samples.
Complete Table 1 by placing an X in each box that you predict will have shown a positive result.

Table 1
Biochemical test Liquid from beaker Liquid inside visking tube
Biuret reagent    
Benedicts    
I2/KI    



4c3 marks

Justify your answers for part (b).

4d1 mark

Describe the colour change that takes place for a positive result with Benedict’s solution.

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5a2 marks

State where bile is produced and stored in the human body.

5b2 marks

Bile salts bind to fat droplets and break them down into smaller fat droplets. Explain how this process makes lipid digestion more efficient.

5c2 marks

The products of protein and carbohydrate digestion require a co-transporter system for absorption into the epithelial cells of the small intestine. The products of lipid digestion can enter by simple diffusion. 

Explain why this is possible.

5d3 marks

Lactose intolerance is a common occurrence in the adult population. An individual who is lactose intolerant no longer produces the enzyme lactase in their ileum. Two students were tested for lactose intolerance. They both fasted for 12 hours before drinking a liquid containing 60 g of lactose. The glucose concentration in their blood was measured for the next 125 mins. The results are shown in Figure 1 below.

Figure 1

m-q5

Suggest which individual is lactose intolerant. Justify your answer.

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1a2 marks

Washing powders often contain many different types of enzymes that hydrolyse substances in stains. An investigation was carried out on washing powder with and without added enzymes to determine how well it was able to remove stains. Figure 1 shows their results.

Figure 1

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The substances that cause the food stains are usually large insoluble proteins. Explain how a biological washing powder removes these stains.

1b4 marks

A journalist was investigating the claims by washing powder manufacturers that stated their product removes all tough stains. Figure 1 shows their results. Use the information in Figure 1 to evaluate the manufacturers claim.

1c3 marks

The manufacturer of biological washing powder wanted to develop a washing powder that was effective across a range of different temperatures. They investigated the effect of temperature on the rates of reaction catalysed by two enzymes, A and B. Figure 2 shows their results. 

Figure 2

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The manufacturer concluded that enzyme B would be the best enzyme to use. Use the results from Figure 2 to evaluate this conclusion. 

1d2 marks

Suggest and explain one other factor the manufacturers should consider when deciding on the best enzyme to include in the biological washing powder.

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2a2 marks

Figure 1 shows a cell commonly found in the small intestine.

Figure 1 

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Identify organelle C and suggest why there are large numbers of organelle C in these cells.

2b2 marks

The structures labelled A can be damaged when people suffer from coeliac disease which is a disease of the human digestive system. They tend to have lower concentrations of amino acids in their blood. 

Explain why they have low concentrations of amino acids in their blood.

2c4 marks

Figure 2 shows one of the ways in which amino acids are absorbed from the small intestine into the blood.

Figure 2

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Cyanide is an inhibitor of mitochondria. In the presence of cyanide, the concentration of  sodium ions in the cell rises and amino acid absorption stops. 

Explain why sodium ions and amino acids will not be absorbed from the lumen of the small intestine in the presence of cyanide. 

2d1 mark

What is the mechanism of movement represented by Q? Explain your answer.

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3a2 marks

Scientists investigated if there was a difference in lactase activity in adult mice who were fed different types of carbohydrate diets as newborn mice. The mice were divided into four groups all of which were fed a standard diet only differing in the carbohydrate content. Table 1 shows their results. 

Table 1

Diet Mean lactase activity / µ mol of lactose digested per hour 
Low glucose 47.8 (± 17.5)
High glucose 173.9 (± 31.2)
Low glycogen 91.3 (± 12.1)
High glycogen 231.5 (± 27.8)

The data is presented with standard deviations for each group. Suggest why the standard deviations differ. 

3b3 marks

A group of scientists concluded that increasing glycogen in the diet in adults was the most effective way to increase lactase activity. Evaluate this conclusion.

3c1 mark

Lactose is often found in milk with many adults unable to digest lactose and suffering from intestinal problems if they drink milk. Figure 1 shows an industrial reactor used to produce lactose-reduced milk.

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Suggest one benefit of immobilising lactase in this reactor. 

3d3 marks

Using Figure 1, explain three reasons why the milk must be passed through the reactor several times.

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4a5 marks

Figure 1 shows some of the events that occur when lipids are digested and absorbed in the small intestine. 

Figure 1

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Use Figure 1 to describe how the large lipid droplet is absorbed into the blood stream. 

4b3 marks

A group of scientists wanted to investigate the effect of lipase and a 11% bile salts solution on the digestion of triglycerides. Figure 2 shows their results.

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Describe and explain the results shown in Figure 2.

4c1 mark

The investigation was repeated at a temperature that was 10 C° lower. Sketch on Figure 3 below the graph you would expect to see at this lower temperature for lipase solution with 11% bile salts.

Figure 3

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4d2 marks

When chylomicrons leave the epithelial cell, they enter small lymphatic capillaries called lacteals. Suggest how chylomicrons leave the epithelial cell and explain your answer. 

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5a3 marks

Bacteria are often used in industries when scientists need large amounts of enzymes.Describe how bacteria divide and suggest why they are used in industry to provide enzymes.  

5b1 mark

Some bacteria are able to secrete proteases outside of their cells. Suggest and explain an advantage of this. 

5c2 marks

Mammals can produce extracellular proteases as well as membrane-bound enzymes such as dipeptidases. Explain why dipeptidases are important in protein digestion. 

5d3 marks

Endopeptidases are enzymes that hydrolyse the internal peptide bonds found in long polypeptide chains whereas exopeptidases hydrolyze terminal peptide bonds. Soybean and other legumes contain chemicals that inhibit endopeptidases such as trypsin. Explain the effects of these chemicals on protein digestion and absorption. 

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