CAIE IGCSE Biology 12.1 Respiration & Energy Use

Practise respiration-and-energy questions on energy uses in organisms, passive-process distractors, respirometer rates and temperature effects.

Exam points

identify active transport, cell division, muscle contraction and nerve impulses as energy uses
reject diffusion, osmosis or evaporation as processes needing respiratory energy
calculate respiration rate from gas-volume change and explain temperature effects on enzymes

Covered syllabus points

12.1.1—Uses of energy in living organisms 12.1.2—Effect of temperature on respiration

[Maximum number: 3]

Fig. 6.1 shows some cells from the shoot tip of an onion, Allium cepa.

Fig. 6.1

The area labelled M is a mitochondrion.

Explain why mitochondria have an important role in dividing cells.

[Maximum number: 1]

One problem with using biomass in the process shown in Fig. 4.1 is that the breakdown stage produces a sugar called xylose and ethanoic acid. Yeast cannot use xylose, and ethanoic acid is toxic to yeast.

Scientists genetically engineered a type of yeast that can use xylose and ethanoic acid.
Fig. 4.2 shows the results of one of the trial experiments done by the scientists using their new genetically engineered yeast.

Fig. 4.2

The experiment was done at $30^{\circ} \mathrm{C}$ .

The scientists repeated the experiment at $20^{\circ} \mathrm{C}$ .
Predict the results that you would expect for the concentration of ethanol.

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Covered syllabus points

12.1 Respiration question 1

12.1 Respiration question 2