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 Original colour Solution in the flask 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) Tube Hydrogencarbonate indicator 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 A B Change in liquid level in U-shaped capillary tube Rises 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 Dependent variable variable (What will you (What will you change?) measure?) Controlled variables (What will you keep constant?) Control (What is the control in this experiment?)
Whether the seeds Temperature as Amount of seeds in The boiled seeds. are living or boiled. recorded by the the vacuum flasks. thermometers. B 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.