Page 150 - Biology Form Two

Biology for Secondary Schools

Cork

Soda lime Black cloth
Bell jar
Thistle funnel To filter pump
FOR ONLINE READING ONLY
Cork Cork

Lime water Lime water
Conical flask Conical flask

Potted plant Polythene paper

Figure 6.13: Experimental set-up to demonstrate respiraion in plants

Note: The black cloth prevents photosynthesis. The polythene paper prevents
carbon dioxide from the soil to interfere with the results. Soda lime absorbs
all carbon dioxide.

2. Apply petroleum jelly to prevent air from entering the apparatus.
3. Note the colour of lime water in both flasks.
4. Switch on the filter pump to draw a stream of air through the apparatus.

5. Observe any changes in the lime water.

Question

What can you conclude from your observation?

Anaerobic respiration
Anaerobic respiration takes place in the absence of oxygen. It releases a relatively
small amount of energy in the cells through the break down of glucose in the
absence of oxygen. Glucose is not completely broken down, thus less energy
is released than during aerobic respiration. It converts the by-products from
glycolysis (pyruvate) to form either ethanol or lactic acid and a small amount
of energy. Anaerobic respiration occurs when cells need energy but there is no
oxygen for aerobic respiration.

Organisms that respire anaerobically are called anaerobes. They include some
bacteria and some fungi. There are two types of anaerobes, which are obligate
anaerobes and facultative anaerobes.

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