Antibiotics (Edexcel International A Level (IAL) Biology): Exam Questions

Exam code: YBI11

30 mins3 questions
1a
2 marks

Antibiotics are medicines used to treat some medical conditions.

The table shows some medical conditions and whether or not antibiotics are needed to treat the condition.

Medical condition

Are antibiotics needed to treat the condition?

  Impetigo

yes

  Whooping cough

yes

  Middle ear infections

sometimes

  Sinus infections

sometimes

  Multiple sclerosis

no

  Rheumatoid arthritis

no

Explain the use of antibiotics to treat these conditions.

1b
1 mark

The graph shows the effect of three drugs, J, K and L, on the number of bacteria in a culture.

q2b-unit-4-january-2021-edexcel-ial-biology

Which row of the table describes each of these three drugs?

drug J

drug K

drug L

☐ A

not an antibiotic

  bactericidal antibiotic

  bacteriostatic antibiotic

☐ B

not an antibiotic

  bacteriostatic antibiotic

bactericidal antibiotic

☐ C

  bactericidal antibiotic

not an antibiotic

bacteriostatic antibiotic

☐ D

  bacteriostatic antibiotic

not an antibiotic

bactericidal antibiotic

1c
8 marks

One problem of taking antibiotics is their effect on gut flora.

The diagrams show the effects of three antibiotics, P, Q and R, on the proportion of different types of gut flora.

Each section in each of the diagrams represents a different type of gut flora.

q2c-unit-4-january-2021-edexcel-ial-biology

(i) Explain the role of gut flora in protecting the body from infection.

(2)

(ii) Explain why antibiotics can affect gut flora.

(2)

(iii) The number of type A in gut flora in the absence of antibiotics is 6 000 000.

Estimate the number of type B in gut flora in the absence of antibiotics.

Give your answer in standard form.

(1)

(iv) Deduce the effects of antibiotics P, Q and R on gut flora.

(3)

2a
3 marks

An investigation was carried out into the effectiveness of four different antibiotics (A, B, C and D) against Staphylococcus aureus bacteria using the disc diffusion method. A lawn of S. aureus was created on an agar plate, and paper discs soaked in different antibiotics were placed onto the surface of the agar.

Describe the aseptic technique that should have been used when preparing the bacterial lawn on the agar plate.

2b
2 marks

After placing the antibiotic discs on the agar, the lid of the Petri dish was secured with tape and incubated at 25°C for 48 hours.

Explain two precautions that should be taken when securing and incubating the Petri dish.

2c
3 marks

After 48 hours the diameter of the zone of inhibition around each antibiotic disc was measured. For one disc with antibiotic B, the total diameter of the zone of inhibition was 22 mm. The paper disc itself had a diameter of 6 mm.

Calculate the area of the clear zone only, excluding the area covered by the paper disc, for antibiotic B. Give your answer to 3 significant figures.

2d
4 marks

The experiment was repeated once more. The mean diameters of the zones of inhibition and the standard deviations for each antibiotic are shown below. The diameter of all paper discs was 6.0 mm.

Antibiotic

Mean diameter of zone of inhibition / mm

Standard deviation / mm

A

8.0

1.2

B

22.0

4.5

C

28.0

1.1

D

6.0

0.0

Evaluate the validity of the results gained in this investigation.

3a
4 marks

The graph shows the number of prescriptions of the antibiotic, aminopenicillin, issued in one year.

The graph also shows the percentage of E. coli bacteria that were resistant to aminopenicillin during the same year.

q7b-unit-4-oct-2020-edexcel-ial-biology

Explain the relationship between the number of aminopenicillin prescriptions issued and the percentage of E. coli resistant to aminopenicillin during this one-year period.

Use the information in the graph to support your answer.

3b
3 marks

The results of a survey are shown in the diagram.

q7c-unit-4-oct-2020-edexcel-ial-biology

Explain why the results of this survey are a cause for concern.