Cellular Energetics I - Cellular Respiration
& Fermentation
Exercise 4 - Cellular Respiration
From the
respiration figure it is possible to see that during cellular respiration
oxygen is used while
carbon dioxide is being produced. This relationship is direct in a quantitative
sense, since for every mole of oxygen used one mole of carbon dioxide
is produced. Thus, if respiration proceeds
in a closed system the volume of gas will remain constant even though the composition
of the gas changes. If the liberated carbon dioxide is removed then the volume
of gas in a closed system will decrease. Thus, the amount of the decrease over
time will reflect the amount of carbon dioxide liberated as well as the amount
of oxygen used during respiration. We will make use of this information to measure
the overall rate of respiration in plant material (germinating seeds) and animal
material (flour beetle larvae).
Keeping this information in mind.
several simple respirometers were set up. Each respirometers consists of
a test tube with the test material , pellets of KOH suspended above the material
on glass wool, a set of tubes which join the test tube to a u-tube with fluid
and a 1 cc syringe.
The respirometers were used to measure the use of oxygen
under the following conditions:
- plant material (germinating seeds) at 20°C
- plant material (germinating seeds) at 30°C
- animal material (flour beetle larvae) at 20°C
- animal material (flour beetle larvae) at 30°C
For your lab assignment assume 3.5 grams of larve used 0.8 mL of O2 in 45 minutes.
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to View the Results
Answer the following questions pertaining to the experiment:
- If you conducted the experiment in the dark would you expect different
results?
- How could you prove that Carbon dioxide is given off during respiration?
- Which respired more rapidly, the seeds or the flour worms? Explain the
difference.
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The flour beetle more-or-less conforms to the temperature of its environment.
This is referred to as being poikilothermic or ectothermic. Humans
are one of a large group of animals which are termed homeothermic
or endothermic. This
means that they maintain their body temperature around a certain value (for
example 37°C in the case of humans).
Answer the following questions:
- How would changes in environmental temperature (in either an upward
or a downward direction) affect respiration in a homeothermic animal)?
- Name the specific regions of a cell where the various steps of catabolism take
place.
- If you oxidize glucose with a flame in a bowl, a large amount of heat
is given off. Why doesn't the oxidation of glucose in a cell injure the cell
with heat?
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First published Sept 95: Modified June 2019
Copyright © Michael Shaw 2019 (Images and Text)
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