CAIE IGCSE Biology 21.2.7 Conditions That Need to Be Controlled Questions

Practise explaining how temperature, pH, oxygen, nutrients, mixing and waste are controlled during fermentation.

Exam points

Explain how a water jacket and pH control maintain conditions for enzyme activity.
Link aeration and stirring to oxygen supply and uniform mixing of fermenter contents.
Use nutrient and product-concentration graphs to infer nutrient depletion or waste accumulation.

[Maximum number: 5]

Bacteria are useful in biotechnology and genetic engineering.
Fig. 6.1 shows a photomicrograph of a bacterium.

Fig. 6.1

(a)

Genetically modified bacteria are often grown in fermenters.

[ 5 ]

(i)

Suggest why steam is used to clean fermenters.

[ 2 ]

(ii)

State three conditions inside a fermenter that are measured and controlled.

1

2

3

[ 3 ]

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