Biology 5090/62 — October/November 2022

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

questions

marks

minutes

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

Q118MUse of Techniques, Apparatus and MaterialsObservations and MeasurementsExperimental ContextsPlanning Experiments and InvestigationsFree sample

Yeast is a microorganism that can use the sugar sucrose to obtain energy for growth. When yeast is added to a sucrose solution it grows, producing bubbles of a gas that cannot escape from the mixture and so the volume of the mixture increases.

A student investigated the effect of varying the concentration of sucrose solution on the growth of yeast, by measuring this increase in volume.

He started with a supply of 5% sucrose solution.

He labelled four test-tubes, A, B, C and D.

(a)

(i)

State what you would use to label the test-tubes.

______

(ii)

He followed this procedure:

add $15\text{ cm}^3$ of 5% sucrose solution to test-tube A
add $9\text{ cm}^3$ of 5% sucrose solution and $6\text{ cm}^3$ of distilled water to test-tube B to produce $15\text{ cm}^3$ of 3% sucrose solution
add $3\text{ cm}^3$ of 5% sucrose solution and $12\text{ cm}^3$ of distilled water to test-tube C to produce $15\text{ cm}^3$ of 1% sucrose solution
add $15\text{ cm}^3$ of distilled water to test-tube D.

He measured the volumes of 5% sucrose solution and distilled water with a small measuring cylinder. Describe how he could ensure that the dilutions produced were correct.

______

(b)

He set up a beaker as a water-bath at a temperature of $40\,^\circ\text{C}$ .

He added $1\text{ g}$ of yeast to each test-tube and stirred each mixture well.

The four test-tubes were then placed in the water-bath.

He decided that any change in height of the mixture in each test-tube would be an indication of a change in its volume and so of how much the yeast had grown.

He measured the total increase in height of the mixtures in the test-tubes in $\text{mm}$ after 5 minutes and 10 minutes and recorded them in his notebook.

Fig. 1.1

(i)

Complete the table using the information given.

test-tube	______
	after 5 minutes	after 10 minutes
A
B
C
D

(ii)

Use his results to describe the effect of sucrose concentration on yeast growth.

______

(iii)

Suggest an explanation for the results in test-tube D.

______

(c)

(i)

He wanted to carry out this investigation at a temperature of $40\,^\circ\text{C}$ . The thermometers in the diagram show the temperature of the water when he first placed the test-tubes in the water-bath (E) and after 10 minutes (F).

Fig. 1.2

Record the temperature when the test-tubes were first placed in the water-bath.

______

Record the temperature after 10 minutes.

______

(ii)

Suggest how the temperature of the yeast mixtures could have been maintained at $40\,^\circ\text{C}$ throughout the investigation.

______

(d)

Yeast uses sucrose to obtain energy for growth.

Suggest a simple method to demonstrate that this process requires enzymes to be present in the yeast.

______

The rest of this paper

2 more questions

Q2Analysis, Conclusions and Evaluation · Planning Experiments and Investigations12M
Q3Microscopy and Biological Drawing10M

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