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Respiration



What do organisms use energy for:

Growth
Movement ­ e.g. breathing, running, thinking,
growing towards the light (cress seedlings),
flowering, seed production
Generating heat energy ­ for warmblooded
animals, e.g. birds and mammals
Reproduction
Nutrition
Excretion
Sensitivity

Where does the energy come from:

The breakdown of food molecules ­…

Page 2

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Living organisms, both plants and animals, carry
out respiration 24 hours per day, 7 days per week,
i.e. all the time.


Sources of Chemical Energy

Plants are the ONLY organisms which can convert solar
energy into chemical energy.

All organisms on the planet therefore are either plants which
produce their…

Page 3

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C6H12O6 +6O2 6CO2 + 6H20 with the
release of a
high level of energy

· recall the word equation for anaerobic respiration in plants
and in animals (B2.26).



Anaerobic Respiration ­ the breakdown of glucose
without oxygen. Because of this, the glucose is only partly
broken down, so far less…

Page 4

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2)In Yeast

­ anaerobic respiration (fermentation) is normal for yeast

Glucose >ethanol + carbon dioxide
with the release of a
small amount of energy
· describe the differences between aerobic and anaerobic
respiration (B2.24)

Aerobic respiration Anaerobic respiration

Requires oxygen No oxygen required

Produces water and Produces lactic acid in…

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· understand that respiration continues during the day and
night, but that the net exchange of carbon dioxide and
oxygen depends on the intensity of light (B2.28)



How did we show that carbon dioxide is given out
during respiration.

There are 2 Carbon dioxide Indicators:

Limewater clear + colourless >cloudy…

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At dawn and dusk (low light levels) the oxygen generated by
photosynthesis is sufficient for respiration needs.........and
the CO2 released by respiration is sufficient for
photosynthesis.

Experiments using bicarbonate indicator.

Specimen Tubes containing Bicarbonate Indicator
after being under light for 40 minutes.







From left to right:
1. Indicator with snails…

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From left to right:
1. Indicator with snails only .

2. Indicator with Elodea only.

3. Indicator with snails and Elodea.

4. Control indicator for colour comparison.



As you can see, where plants have light, they photosynthesise
as well as respire. Because this photosynthesis removes
more carbon dioxide than the…

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from respiration is not taken back up for photosynthesis so
the indicator absorbs it and changes colour from red(0.04%
CO2 ) to yellow (CO2 greater than 0.04%).



Other practicals

Collecting carbon dioxide

Place yeast solution in a test tube. Incubate at 35°C.

Place a balloon over the top of the…

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The apparatus above shows a simple respirometer. This
allows us to measure the uptake of OXYGEN as the organisms
in the beaker respire. Here, they are mealworms ­ they could
just as easily be germinating peas, maggots or locusts.

Water bath ­ to maintain a constant temperature for the
mealworms…

Page 10

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This apparatus only measures the change in the volume of
gas ­ which of course will not alter.

By removing the carbon dioxide gas as it is produced, there
will be a lower volume of gas present.

This reduction creates an area of lower pressure in the
capillary tube (i.e.…

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