Digestion & the Digestive System in Humans (WJEC GCSE Science (Double Award): Biology): Exam Questions

The beaker in Image 5 contains 150 cm³ of an unknown solution.

Image 5

Using all the materials shown in Image 5 describe how you would:

1. transfer 10 cm³ of the solution from the beaker to the test tube

2. test it for starch

State the colour change if starch is present.

[6 QER]

Image 4.1 shows the human digestive system.

Image 4.1

Use labelled arrows to identify the following organs on Image 4.1.

(i) gall bladder

(ii) pancreas

Image 4.2 represents a part of the wall of the small intestine. The left side of the diagram represents the contents of the small intestine.

Image 4.2

(i) The only food substance originally in the contents of the small intestine was starch. Explain the presence of glucose in the small intestine.

[2]

(ii) Absorption involves the movement of glucose molecules through the wall of the small intestine.

I. Name the process that enables absorption to take place.

[1]

.......................................................................................

II. In the human body, the glucose moves into a fluid on the right side of the intestine wall. Give the name of this fluid.

[1]

.......................................................................................

(iii)

I. If the only food substance in the contents of the small intestine was protein, state what would be found on the right side of the diagram.

[1]

.......................................................................................

II. Explain your answer.

[2]

In a food test investigation some students were given a beaker containing an unknown solution. They were asked to use two different chemical reagents to identify the foods in the solution. The table below shows some of the observations recorded by one of the students.

Complete the table.

The diagram below shows part of the human digestive system.

On the diagram above label the following:

A pancreas

B bile duct

The diagram below shows five test tubes A – E and their contents. The pH and temperature of each is also shown.

A pupil carried out the following procedure:

• She took a Petri dish containing starch-agar (a set jelly in which starch had been dissolved).

• She cut five small holes in the jelly (holes 1 – 5).

• She put 1 cm³ distilled water from Tube A into hole 1.

• Holes 2 – 5 were each filled with 1 cm³ of a different solution from one of test tubes B, C, D or E.

• After one hour she flooded the Petri dish with iodine solution.

(i) Explain the appearance of the clear areas.

[1]

(ii) State the solution that was added to hole 2. Explain your answer.

[2]

(iii) Which hole contained the contents of tube C? Explain your answer.

Hole number ..............................................

Explanation ......................................................................................................

[4]

State the purpose of tube A, the contents of which was put into hole 1.

Image 2.1 shows the digestive system. Some structures have been labelled.

Image 2.1

Complete the following sentences by underlining the correct word.

(i) Peristalsis in the digestive system causes food to be

digested / moved / absorbed.

[1]

(ii) One organ where peristalsis happens is the

gall bladder / oesophagus / pancreas.

[1]

State the name of the organ labelled in Image 2.1 in which the chemical digestion of protein starts.

(i) The liver makes bile.

On Image 2.1, draw an arrow to label the liver.

[1]

(ii) Bile helps us digest fat.

Complete Table 2.2 by writing true or false against each statement. One has been done for you.

[3]

Table 2.2

Fat is an important part of the diet.

State one function of fat in the body.

Eating excess fat can lead to obesity.

Chitosan is a product that can help people lose weight.

Chitosan stops the digestion of fat.

(i) Explain why taking Chitosan would increase the amount of fat in the waste leaving the body.

[2]

(ii) Suggest one reason why taking Chitosan as part of a diet might be harmful to health.

[1]

Why is it not possible to conclude from the data that Paul's low fitness index is due to obesity?

Image 5.1 shows part of the digestive system.

Image 5.1

Label parts A to C on Image 5.1.

A .................................................

B .................................................

C .................................................

Explain why carbohydrase cannot digest fat.

Image 5.3 shows the structure of the lining of the small intestine of a healthy individual and an individual with coeliac disease. Coeliac disease causes a flattening of the villi lining the small intestine.

Image 5.3

Use Image 5.3 to explain why individuals who have coeliac disease are unable to fully absorb their digested food.

Dried milk powder and whey powder both contain protein. A weight lifter wanted to determine which would be more beneficial in his diet for his performance.

In order to do this, he first prepared equal volumes of known concentrations of protein for comparison. He then added 5 cm³ of 5% enzyme solution to each and recorded the time taken for the protein-enzyme mixture to go from cloudy to clear. This colour change is shown in Image 7.1.

Image 7.1

His results are shown in the Graph 7.2.

Graph 7.2

(i) State the independent and dependent variables.

[2]

Independent variable .................................................................................

Dependent variable ......................................................................................................................

(ii) Name the type of enzyme which was added to the protein and explain the change in appearance from cloudy to clear.

[2]

(iii) State one source of uncertainty in the experimental method and suggest how it could be overcome.

[2]

The weight lifter then carried out the experiment using a sample of dried milk powder followed by a sample of whey powder. The milk powder took 72 seconds to clear and the whey powder took 100 seconds to clear.

Use data from Graph 7.2 to explain why the weight lifter concluded he should use whey powder rather than dried milk powder in his diet to improve his performance.

Image 5.1 shows the digestive system.

Image 5.1

Choose named structures from Image 5.1 to complete Table 5.2.

Table 5.2

Visking tubing has small holes in its wall which only allow small molecules to pass through.

Dafydd studies a computer model which uses Visking tubing to show part of the digestive system in action.

The stages involved are shown in Image 5.3.

Image 5.3

Using all the information shown in stages 1, 2, 3 and 4, explain how glucose appears in the water outside the Visking tubing in stage 4.

The nutrition information in Table 6.1 is taken from a pack of dried pasta.

Table 6.1

(i) Calculate the value for unsaturated fats. Write your answer in Table 6.1.

Space for working.

[1]

(ii) State the name of the nutrient which makes up most of the carbohydrates in the dried pasta.

.......................................................................................

[1]

(iii) State the importance of a low-salt diet.

[1]

Lloyd and Emma carried out an experiment to compare the energy values in Table 6.1 with values they obtained using the apparatus shown in Image 6.2.

Image 6.2

They ignited a 1.6 g piece of dried pasta using the Bunsen burner and immediately held the burning pasta at the base of the boiling tube until it stopped burning. The results Lloyd and Emma obtained are shown in Table 6.3.

Table 6.3

(i) Use the following formula to calculate the energy released per gram of food (kJ). Write your answer in Table 6.3.

$\mathrm{Energy}\mathrm{released}\mathrm{per}\mathrm{gram}\left(\mathrm{kJ}\right)=\frac{\mathrm{volume}\mathrm{of}\mathrm{water}\left(\mathrm{cm}3\right)\times \mathrm{temperature}\mathrm{increase}(°\mathrm{C})\times 0.0042}{\mathrm{mass}\mathrm{of}\mathrm{pasta}\mathrm{sample}\left(\mathrm{g}\right)}$

[2]

(ii)

I. State how the energy content of dried pasta in Table 6.3 compares to the energy content indicated in Table 6.1. You must use numerical data in your answer.

[2]

II. Give one reason for the difference between the energy content of dried pasta obtained by Lloyd and Emma, as shown in Table 6.3 and the energy content indicated in Table 6.1.

[1]

(iii) Evaluate the arrangement of the apparatus shown in Image 6.2 by identifying one source of error.

[1]

(i) State the products of protein digestion.

.......................................................................................................

[1]

(ii) State the part of the digestive system that absorbs digested food molecules.

.......................................................................................................

[1]

Protein digestion starts in the stomach.

Students investigated protein digestion. They set up five tubes A to E, as shown below.

The students measured the percentage protein digested at one hour. The results are shown in the table.

(i) Compare the results for tubes A and D. State the conclusion that can be made about the digestion of protein.

[1]

(ii) State the conclusions that can be made about the contents of the liquid from the stomach in Tube B.

[2]

(iii) All the 1% protein added to Tube A had been fully digested after one hour.

State why the contents of Tube A would still test positive for protein.

[1]

(iv) The students carried out a similar investigation, but instead of using 0.1% protease, they used 5 cm3 of 0.1% lipase in both tubes A and C.

They found there had been no digestion of protein in either tube.

Use your knowledge of enzyme structure and function to explain the results that the students obtained.

[2]

(v) State one further variable that should be controlled during this investigation.

..............................................................................................................

[1]

Carwyn and Anwen are year 10 students who are concerned that they are overweight. They think that their health may be affected in later life. They both agree to help each other follow a balanced diet.

They research the topic on the Internet and find the following information:

As part of a healthy balanced diet, it is recommended that people of their age should be eating the following every day:

Carwyn does not want more than one third of his recommended energy input per day to come from starchy carbohydrates.

For his evening meal he has decided to have pasta, the only carbohydrate he eats in the day. He wants to know the energy content of 1 g of pasta in order to calculate how much pasta to allow himself in his evening meal.

Carwyn and Anwen used the following simple calorimeter to measure the energy content of a 7 g piece of dried pasta.

The table shows one set of results they obtained.

(i) Complete the table above by using the following formula.

$\text{Energy released per gram (J)}=\frac{{\text{volume of water (cm}}^3\text{)}\times \text{temp increase (°C)}\times 4.2}{\text{mass of pasta sample (g)}}$

[2]

(ii) Calculate the mass of pasta Carwyn can eat in his evening meal to get one third of his daily energy intake.

Mass of pasta = ................................... g

[2]

(iii) Carwyn was surprised to discover that he could have that much pasta for his evening meal. Anwen said 'there's something wrong, that's over ten bags of pasta! We have to evaluate our scientific method to find where the error lies.'

Evaluate the design of the apparatus and identify one source of error.

[1]

The graph shows the activity of three enzymes, X, Y and Z at different pH values.

(i) State the enzyme (X, Y or Z) that is active only in acid conditions.

...................................................

[1]

(ii) Underline the pH range at which both enzymes Y and Z work.

Between pH 4.5 and pH 8.0

Between pH 4.5 and pH 7.5

Between pH 6.0 and pH 7.5

[1]

(iii) Enzyme Z is found in saliva.

State a structure in the body that produces saliva.

.........................................................................

[1]

Describe the functions of bile and lipase in the breakdown of fats.

The Body Mass Index (BMI) is one way of measuring whether a person is a healthy mass for their height. The result gives an indication of whether the person is a healthy mass, and if not, how overweight or underweight they are.

The BMI is calculated from the mass and height of a person. It is calculated using the following equation:

$\text{BMI}=\frac{\text{body mass}}{{\text{height}}^2}$

where body mass is measured in kilograms and height in metres.

The chart shows the BMI categories based on the World Health Organisation data. The dashed lines represent subdivisions within a major category. For example, the underweight category is subdivided into severe, moderate and mild.

From the chart, state how many subdivisions there are within the obese category.

number of subdivisions in the obese category = ...................

The table below shows some biometric data for three teachers at a school.

(i) Calculate the BMI for Peter and write the answer in the table.

[2]

(ii) Use the chart opposite to allocate a major BMI category to Sharon and Peter and write the answer in the table above.

[1]

Iorwerth wants to reduce his BMI. State two ways in which he could alter his diet in order to achieve this.

I. ........................................................................................................................

II. .......................................................................................................................

Explain why lack of exercise can result in obesity.

The diagram shows the human digestive system.

State which of the labelled parts in the above diagram absorbs digested food molecules.

......................................................................................................................