GCSE Edexcel Biology Core Practical: Investigating antibiotics & antiseptics: Streptococcus pyogenes is a bact

Question

Streptococcus pyogenes is a bacterium that causes communicable infections.

(a) Scientists tested the ability of two antiseptics to kill Streptococcus pyogenes bacteria. They spread Streptococcus pyogenes bacteria on two agar jelly plates and placed a small disc of filter paper containing antiseptic in the centre of each dish. Figure 3 shows the results after 24 hours of incubation.

**Figure 3**

| antiseptic 1 | zone of inhibition |
|---------------|------------------|
| radius (mm)  | 12               |
| area (mm²)   | 452              |

(i) Calculate the area of the zone of inhibition for antiseptic 2.
Give the answer to 3 significant figures.
($\pi = 3.14$)

zone of inhibition for antiseptic 2 = ..................................... mm²

(ii) Explain which antiseptic is the most effective.

(iii) After the bacteria were spread on the plates, both plates were incubated for 24 hours at 37°C.
Give a reason why the plates were incubated at 37°C.

(b) The wire loop used to spread bacteria on an agar plate was heated in a Bunsen burner flame before being used.
Explain why this aseptic precaution was used.

Streptococcus pyogenes is a bacterium that causes communicable infections - Edexcel - GCSE Biology - Question 2 - 2016 - Paper 1

Worked Solution & Example Answer:Streptococcus pyogenes is a bacterium that causes communicable infections - Edexcel - GCSE Biology - Question 2 - 2016 - Paper 1

Calculate the area of the zone of inhibition for antiseptic 2.

Explain which antiseptic is the most effective.

Give a reason why the plates were incubated at 37°C.

Join the GCSE students using SimpleStudy...