Some students investigated the effect of two sugars on the activity of yeast. Solution A was $10\text{ cm}^3$ of $10\%$ glucose in water. Solution B was $10\text{ cm}^3$ of $10\%$ sucrose in water. Fig. 1.1 shows the apparatus that was used. - $3\text{ g}$ of dried yeast was added to solution A in a test-tube and shaken, then left standing in a beaker of warm water for five minutes. - The delivery tube was attached and the number of bubbles released in one minute was counted…

Biology 5090/62 — October/November 2013

Cambridge O-Level · Alternative to Practical · worked solutions for every part, with the mark scheme

questions

marks

minutes

Topics Experimental Contexts · Analysis, Conclusions and Evaluation · Observations and Measurements · Planning Experiments and Investigations · Use of Techniques, Apparatus and Materials · Microscopy and Biological Drawing

Q121MExperimental ContextsAnalysis, Conclusions and EvaluationUse of Techniques, Apparatus and MaterialsObservations and MeasurementsPlanning Experiments and InvestigationsMicroscopy and Biological DrawingFree sample

Some students investigated the effect of two sugars on the activity of yeast.
Solution A was $10\text{ cm}^3$ of $10\%$ glucose in water.
Solution B was $10\text{ cm}^3$ of $10\%$ sucrose in water.

Fig. 1.1 shows the apparatus that was used.

Fig. 1.1

$3\text{ g}$ of dried yeast was added to solution A in a test-tube and shaken, then left standing in a beaker of warm water for five minutes.
The delivery tube was attached and the number of bubbles released in one minute was counted and recorded as 'first count' in Table 1.1.
The test-tube containing the mixture was gently shaken again, while still in the beaker of warm water.
The number of bubbles released was counted again for one minute and recorded as the 'second count' in Table 1.1.
A third count was taken in the same way.

This whole procedure was repeated using another $3\text{ g}$ of dried yeast mixed with solution B.

The results were recorded as shown in Table 1.1.

Table 1.1

solution	number of bubbles of gas released in one minute: first count	number of bubbles of gas released in one minute: second count	number of bubbles of gas released in one minute: third count
A glucose in water	13	12	10
B sucrose in water	36	34	32

(a)

Using data from Table 1.1, describe what these results show about the effect of glucose and sucrose on the activity of yeast.

(b)

(i)

State the name of the gas that was released to form the bubbles.

______

(ii)

Describe a simple test for the gas you have named.

(iii)

State the name of the process that was taking place in the yeast to produce this gas.

______

(c)

(i)

Suggest why the yeast and sugar solution had to be left for 5 minutes.

(ii)

Explain why the bubbles were counted three times for each solution.

(iii)

Suggest why the test-tubes were shaken between the counts.

(iv)

List the factors that were kept constant during this investigation.

(d)

Fig. 1.2 shows a yeast cell dividing.

Fig. 1.2

(i)

Make a drawing of the yeast cell dividing shown in Fig. 1.2.

(ii)

On Fig. 1.2, draw a line between the letters P and Q.

Measure and record this length ______ $\text{mm}$

On your drawing, draw a line similar to the line PQ.

Measure and record this length ______ $\text{mm}$

Calculate the magnification of your drawing compared to the actual size of the cell.

Show your working.

magnification $\times$ ______

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