Biology 9700 · AS & A Level · Respiration

Respiration — practice question

Yeast cells are able to respire in anaerobic conditions.
(a(i))[4]

Outline the way in which yeast carry out respiration in anaerobic conditions.

(a(ii))[2]

Explain why respiration in anaerobic conditions is an advantage for yeast.

(b)[2]

A practical was carried out to compare the GM strain of yeast with yeast that had not been genetically modified (non-GM strain). In this practical, the starch suspension after heating to $80\,^{\circ}\text{C}$ was cooled to $30\,^{\circ}\text{C}$ before yeast cells were added. The results are shown in Fig. 2.1. With reference to Fig. 2.1, describe the pattern in ethanol production for the GM strain compared with the non-GM strain.

(c)[2]

The rate of ethanol production is similar in the lower temperature method and the higher temperature method. Suggest why the lower temperature method gives a similar rate of ethanol production to the higher temperature method.

(d)[1]

Suggest one reason why the high temperature method costs more to carry out.

Worked solution & mark scheme

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