Ch 22 Respiration
Practical 22.1 Examination of the structure of
mitochondria
Results (p. 22-2)
Questions (p. 22-2)
1
Muscle cells and liver cells.
2
a
The highly folded inner membrane provides a large surface area to pack more
enzymes that catalyse the reactions of respiration.
b
The mitochondrial matrix contains enzymes for respiration. It provides a
fluid medium for reactions to take place.
Practical 22.2 Investigation of carbon dioxide production
in a living mouse
Results (p. 22-4)
Flask
Solution in the flask
Original colour
Final colour
A
Colourless
Colourless
B
Colourless
Colourless
C
Colourless
Milky
Questions (p. 22-4)
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.
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
microorganisms 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 (p. 22-5)
The living mouse gives out carbon dioxide.
Practical 22.3 Investigation of carbon dioxide production
in germinating seeds
Results (p. 22-7)
Hydrogencarbonate indicator
Tube
Original colour
Final colour
A
Red / orange
Yellow
B
Red / orange
Red / orange
Questions (p. 22-7)
1
To provide the necessary amount of water for germination.
2
To kill the microorganisms 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 (p. 22-7)
The geminating seeds give out carbon dioxide.
Practical 22.4 Investigation of heat production in a living
mouse
Results (p. 22-9)
Arm
Change in liquid level in U-shaped capillary tube
A
Rises
B
Falls
Questions (p. 22-9)
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 (p. 22-10)
Heat is produced by the living mouse.
Practical 22.5 Design an investigation of heat production in
germinating seeds
Design and perform an experiment (p. 22-12)
1
Put the vacuum flasks in an inverted position.
2
Plug the openings of the vacuum flasks with cotton wool.
A
Identifying variables
Independent
variable
(What will you
change?)
Dependent
variable
(What will you
measure?)
Controlled
variables
(What will you
keep constant?)
Control
(What is the
control in this
experiment?)
Whether the seeds
are living or boiled.
B
Temperature as
recorded by the
thermometers.
Amount of seeds in The boiled seeds.
the vacuum flasks.
Designing the set-up
(Answer varies with Ss.)
C
Collecting data
1
(Answer varies with Ss.)
2
Use more seeds.
Remove the seed coats of the seeds.
3
Run the experiment for a longer period of time.
Repeat the experiment for a few more times.
D
Risk assessment and safety precautions
1
(Answers depend on the design.)
2
(Answers depend on the design.)
Write an experimental report (p. 22-14)
Objective
To find out if heat is produced by germinating seeds.
Apparatus and materials
2 vacuum flasks
2 thermometers
cotton wool
2 stands and clamps
soaked germinating seeds (surface
sterilized)
boiled seeds (surface sterilized)
Procedure
1
Set up the two vacuum flasks as shown below.
2
Note the temperature of each vacuum flask at the start of the practical.
3
Leave the set-ups undisturbed for a day.
4
Record any increase in temperature in the vacuum flasks.
Results
Temperature in flask A increases. Temperature in flask B remains unchanged.
Analysis and discussion
1
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 germinating seeds. This is because the microorganisms on the seeds also
respire and produce heat.
b
At first, the temperature would remain unchanged. When microorganisms
start to grow on the seeds, the microorganisms carry out respiration and
produce heat. This leads to a rapid increase in temperature at the later time of
the practical.
3
(Answer varies with Ss.)
Conclusion
Heat is produced by the germinating seeds.
Practical 22.6 Demonstration of anaerobic respiration in
germinating seeds
Results (p. 22-19)
1
The oil level drops.
2
It changes from red / orange to yellow.
Questions (p. 22-19)
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 (p. 22-20)
The germinating seeds respire anaerobically and release carbon dioxide.