Certificate Biology - New Mastering Basic Concepts
Suggested answers to Activity Books Ch 8
Chapter 8
Respiration
Practical 8.1
Investigation of carbon dioxide production in a living
mouse
(Bk 1, p.130)
Results
Solution in the flask
Flask
Original colour
Final colour
A
Colourless
Colourless
B
Red / orange
Purple
C
Red / orange
Yellow
Questions
1
To absorb carbon dioxide from the incoming air. Any carbon dioxide detected in flask C will
therefore be due to the mouse.
2
Flask B: To test whether there is any carbon dioxide in the air entering the bell jar.
Flask C: To test whether there is any carbon dioxide in the air leaving the bell jar.
(Bk 1, p.131)
3
Carbon dioxide is absent in the air entering the bell jar.
4
Carbon dioxide is released by the mouse.
5
Set up a similar apparatus without putting a mouse in the bell jar.
6
Wrap the pot with a plastic bag. Otherwise, carbon dioxide released by the micro-organisms in
the soil will affect the results.
Cover the bell jar with a black cloth. Otherwise, the plant will absorb carbon dioxide for
photosynthesis and this will affect the results.
Conclusion
The living mouse gives out carbon dioxide.
Practical 8.2
Investigation of carbon dioxide production in living
germinating seeds
(Bk 1, p.132)
Results
Lime water in tube A changes to milky. Lime water in tube B remains colourless.
 Oxford University Press 2005
Page 1 / 8
Certificate Biology - New Mastering Basic Concepts
Suggested answers to Activity Books Ch 8
Questions
1
To provide the necessary amount of water for germination.
2
To kill the micro-organisms on the surface of the seeds. Otherwise, carbon dioxide released by
them during respiration will affect the results.
3
As a control to show that only living seeds release carbon dioxide.
Conclusion
The living seeds give out carbon dioxide.
Practical 8.3
Investigation of heat production in a living mouse
(Bk 1, p.134)
Results
The liquid level in arm A rises. The liquid level in arm B falls.
Questions
1
To prevent heat loss from the chambers.
2
To equalize the pressure on both sides of the U-shaped capillary tube. This ensures that both
liquid levels are the same at the start of the practical.
3
Heat is produced by the mouse and it warms up the air in the thin-walled test tube.
The air in the test tube expands and results in an increase in pressure. This pushes the air out of
the test tube and hence forcing the liquid level in arm B downwards.
Since there is no temperature change in the control (the side without the mouse), the falling of
the liquid level in arm B leads to a rise of the liquid level in arm A.
4
No. It is because the mouse will use up all the oxygen inside the chamber and die.
5
A capillary tube with a narrow bore is more suitable for this practical because it gives a more
obvious result.
6
The change in liquid level is smaller. This is because the frog has a lower metabolic rate and less
heat is released from its body.
Conclusion
Heat is produced by the living mouse.
 Oxford University Press 2005
Page 2 / 8
Certificate Biology - New Mastering Basic Concepts
Suggested answers to Activity Books Ch 8
Practical 8.4 Design an investigation of heat production in living
germinating seeds
(Bk 1, p.135)
Design and perform an experiment
1
Amount of seeds in the vacuum flasks.
2
Whether the seeds are living or boiled.
3
Temperature as recorded by the thermometers.
4
The boiled seeds.
5
(Answer varies with Ss.)
6
Put the vacuum flasks in an inverted position.
Plug the openings of the vacuum flasks with cotton wool.
7
Use more seeds.
Remove the testa of the seeds.
(Bk 1, p.136)
8
Run the experiment for a longer period of time.
Repeat the experiment for a few more times.
9
Put the bulbs of the thermometers in the seeds, not the air inside the vacuum flasks.
Make sure that the seeds completely cover the bulbs of the thermometers.
Do not fill up the whole vacuum flasks with seeds or there will not be enough air for
the seeds to carry out respiration.
Write an experimental report
Objective
To find out if heat is produced by living germinating seeds.
Procedure
1
Set up the two vacuum flasks as shown.
2
3
4
Note the temperature of each vacuum flask at the start of the practical.
Leave the set-ups undisturbed for a day.
Record any increase in temperature in the vacuum flasks.
 Oxford University Press 2005
Page 3 / 8
Certificate Biology - New Mastering Basic Concepts
Suggested answers to Activity Books Ch 8
(Bk 1, p.137)
Results
Temperature in flask A increases. Temperature in flask B remains unchanged.
Analysis and discussion
1
Living germinating seeds carry out respiration and produce heat. This leads to an increase in
temperature in the vacuum flask.
Boiled seeds cannot carry out respiration to produce heat. Therefore the temperature remains
unchanged.
2
a
The temperature increase would be much higher than that caused by sterilized and living
germinating seeds. This is because the micro-organisms on the seeds also respire and
produce heat.
b
At first, the temperature would remain unchanged. When micro-organisms start to grow on
the seeds, the micro-organisms carry out respiration and produce heat. This leads to a rapid
increase in temperature at the later time of the practical.
3
Vacuum flasks are well insulated to prevent heat loss or gain.
4
(Answer varies with Ss.)
Conclusion
Heat is produced by the living germinating seeds.
Practical 8.5
Demonstration of anaerobic respiration in germinating
seeds
(Bk 1, p.139)
Results
1
The oil level drops.
2
It changes to yellow.
Questions
1
To hold the seeds in position and prevent them from falling down.
2
It is because water contains dissolved oxygen and the seeds would then be able to respire
aerobically.
3
To ensure the seeds respire anaerobically.
4
The germinating seeds release gas and it forces the oil level downwards.
5
The gas released from the germinating seeds is carbon dioxide.
6
Set up a similar apparatus and replace the soaked germinating seeds with some surface sterilized
and boiled seeds.
Conclusion
The germinating seeds respire anaerobically and release carbon dioxide.
 Oxford University Press 2005
Page 4 / 8
Certificate Biology - New Mastering Basic Concepts
Suggested answers to Activity Books Ch 8
Practical 8.6 Design an investigation of alcoholic fermentation in yeast
(Bk 1, p.140)
Design and perform an experiment
1
Anaerobic condition.
2
Boil the glucose solution to drive out the dissolved air.
Add a layer of paraffin oil on top of the mixture of glucose and yeast.
(Bk 1, p.141)
3
Temperature, pH, volume of glucose solution, etc.
4
Whether the yeast is living or dead.
5
The production of ethanol, carbon dioxide or heat.
6
1
2
3
Detect the production of ethanol by fanning the mixture and smell the air.
Detect the production of carbon dioxide by bubbling the gas released from the mixture
through red hydrogencarbonate indicator or lime water.
Detect the production of heat by observing any increase in temperature of the mixture.
7
Boiled yeast suspension.
8
(Answer varies with Ss.)
9
As alcoholic fermentation involves enzymes, provide the optimum temperature and pH can help
obtain faster results.
10
Repeat the experiment a few more times.
11
Cool down the boiled glucose solution in a closed container before mixing in the yeast.
Otherwise, the living yeast will be killed by the high temperature.
(Bk 1, p.142)
Write an experimental report
Objective
To study alcoholic fermentation in yeast.
Procedure
1
Boil the glucose solution. Cool it down in a closed container and add in the yeast suspension.
2
Set up the apparatus as shown.
3
4
Replace yeast suspension with boiled yeast suspension in another set-up.
Record the temperature of the mixture.
 Oxford University Press 2005
Page 5 / 8
Certificate Biology - New Mastering Basic Concepts
5
Suggested answers to Activity Books Ch 8
6
Leave the set-ups for a few hours. Notice any change in the temperature of the mixture and
colour of the hydrogencarbonate indicator.
Remove the stoppers from the vacuum flasks. Fan the air coming out from flasks with the hand
and smell the air.
Results
Change in temperature
Colour change in
hydrogencarbonate indicator
Smell of air
Yeast suspension
Boiled yeast suspension
From 25 °C to 30 °C
No change
From red to yellow
No change
Like alcohol
No smell
(Bk 1, p.143)
Analysis and discussion
1
Yes. In the presence of oxygen, yeast can respire aerobically and no ethanol is produced.
Keeping out the oxygen ensures only alcoholic fermentation (anaerobic respiration) is carried
out.
2
Vacuum flasks are well insulated. They can prevent the loss of heat produced from alcoholic
fermentation.
3
No. It is because any living yeast is killed by the high concentration of ethanol produced or the
increased temperature. Glucose in the mixture may also be used up.
4
(Answer varies with the design.)
Conclusion
Under anaerobic condition, yeast carries out alcoholic fermentation to produce ethanol and carbon
dioxide. Heat is also given out in the process.
STS connection 8.2 Degree of dependence on anaerobic respiration of
different sports
(Bk 1, p.145)
Task 1
1
Jogging mainly depends on aerobic respiration to supply the energy, whereas lifting weights
mainly depends on anaerobic respiration.
2
To supply more oxygen for ATP production.
To facilitate the removal of the carbon dioxide produced from aerobic respiration.
3
To allow the breakdown of lactic acid produced from anaerobic respiration.
4
Jogging. It mainly depends on aerobic respiration to supply the energy and fats are burnt in the
process to produce ATP.
 Oxford University Press 2005
Page 6 / 8
Certificate Biology - New Mastering Basic Concepts
Suggested answers to Activity Books Ch 8
(Bk 1, p.146)
Task 2
Percentage of dependence for energy (%)
Sport
Aerobic respiration
Anaerobic respiration
Aerobic dance
90
10
100 m sprint
10
90
Tennis
20
80
Basketball
30
70
Football
10
90
50 m swimming
5
95
1500 m swimming
80
20
Exercise 8
(Bk 1, p.147)
Multiple-choice questions
1
C
2
D
3
B
4
D
7
C
8
D
9
D
10
B
5
D
6
C
(Bk 1, p.148)
Structured questions
1
a
Mitochondrion (1m)
b
The inner membrane is highly folded, with many finger-like structures. (1m)
It provides a larger surface area for respiratory enzymes to attach and carry out respiration.
(1m)
c
Nerve cells — much energy are needed for impulse transmission. /
Liver cells — much energy are needed to breakdown proteins or toxins. /
Sperm cells — much energy are needed for swimming towards the egg. (Any 2, 1m each)
d
Glucose is completely broken down in the former condition. (0.5m)
Glucose is partly broken down in the later condition. (0.5m)
Less energy is produced in the later condition than the former condition. (1m)
Ethanol / lactic acid is produced in the later condition but not in the former condition. (1m).
(Bk 1, p.149)
2
a To absorb the carbon dioxide in the incoming air. (1m)
b
To ensure the incoming air is free of carbon dioxide. (1m)
c
i
The hydrogencarbonate indicator will change from orange / red to purple. (1m)
It is because all the carbon dioxide in the incoming air has been absorbed by the
potassium hydroxide solution. (1m)
ii
The hydrogencarbonate indicator will change from orange / red to yellow. (1m)
It is because the mouse respires and gives out carbon dioxide. (1m)
 Oxford University Press 2005
Page 7 / 8
Certificate Biology - New Mastering Basic Concepts
Suggested answers to Activity Books Ch 8
d
Use the same set-up with the mouse removed / replaced by a dead and sterilized mouse.
(1m)
e
Cover the whole jar with a black cloth. (1m)
Wrap the pot with a plastic bag. (1m)
(Bk 1, p.150)
3
a Carbon dioxide (1m)
b
Yeast C (1m)
c
Use the same set-up with the yeast replaced by boiled (0.5m) and sterilized (0.5m) yeast.
d
It was because the substrates (i.e. glucose) are used up (1m), and the accumulated alcohol is
toxic to the yeast (1m).
e
Increase the concentration of glucose solution a little / Increase the temperature a little /
Increase the yeast concentration / Stir the mixture (Any 3, 1m each)
 Oxford University Press 2005
Page 8 / 8