Introduction to respiration
Teaching notes
This resource is the perfect introduction to respiration in which students discover
aerobic and anaerobic respiration for themselves through a series of straightforward
activities. This activity is aimed at high ability students. The activities are arranged as
a circus of eight stations around the room. There is a worksheet which students should
fill in as they visit each station. The answers could be provided at each station in an
envelope or back to back with the activity sheet in a plastic wallet.
Equipment required
Station 2 - beaker of respiring yeast
Station 3 - models of generalised animal and plant cells
Station 6 – The experiment needs to be set up as a dummy so that students can predict
the results. 4 test-tubes set up as below, but with pink coloured water in place of the
indicator solution.
Station 7 - flasks with boiled and germinating peas set up as diagram below. Or
something to suggest a similar experiment e.g. two bunged opaque flasks, with
thermometers one containing hot water, and the other containing room temp water.
Station 8 - test-tubes of limewater with straws, one for each student
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Introduction to respiration
Respiration in cells can take place aerobically or anaerobically. The energy released is
used in a variety of ways. Visit the stations around the room to complete this
worksheet.
Equation for aerobic respiration
..........................................................................................................
Equation for anaerobic respiration in animals (used to obtain energy if insufficient
oxygen is reaching the muscles for aerobic respiration)
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Equation for anaerobic respiration in organisms such as yeast
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Station 1: Which types of athletic events require anaerobic respiration? What is the
downside?
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Station 2:

Why will anaerobic respiration eventually kill yeast?
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
What do we use the products of respiration in anaerobic yeast for?
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
Can you name other food products that utilise anaerobic respiration?
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Introduction to respiration
Station 3:

Name the structures used in respiration in animal and plant cells.
………………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………..
Station 4:
 To prevent lactic acid build up, endurance athletes limit their heart rate to
prevent anaerobic respiration. To stay below the lactic acid threshold (the point
where blood lactic acid concentration starts to rise) Jude’s maximum heart rate
needs to be:
…………………………………………………………………………………………………………………
………………………………………………………………………………………………………………..
Station 5:
 During an aerobics class, what would happen to your body temperature and
breathing rate? Why?
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 Aerobic respiration is a series of reactions which can summarised by this
equation.
C6H12O6 + 6O2
glucose
oxygen
→ 6CO2 + 6H2O (+ energy released)
carbon dioxide
water
Does the above equation look familiar – which other process does it remind you of?
…………………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………………………
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Introduction to respiration
Station 6: Hydrogencarbonate indicator is pink. It turns yellow if CO2 is added and
purple if CO2 is removed.
 Colour the indicator in each tube to show the results you would expect to see
after 1 hour.
 Why does the 3rd tube have foil around it?
............................................................................................................
............................................................................................................
 What is the purpose of the 4th tube?
............................................................................................................
Station 7: Which results are for which flask? How do you know?
Time
(hours)
Temperature
(°C)
Flask_____ Flask_____
0
15
15
12
15
20
24
15
25
36
15
29
48
15
31
60
15
33
72
15
33
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Introduction to respiration
Station 8: Limewater turns cloudy in the presence of CO2

When I breathed into limewater it turned .........................................
this proves that my exhaled air contains ................................... so I am respiring.
Extension tasks:
As the breakdown of glucose is incomplete in anaerobic respiration, much less energy is
released than during aerobic respiration. Research the difference in energy released per
gram of glucose used.
Anaerobic respiration results in an oxygen debt – what does this mean?
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Introduction to respiration
Station 1 – information sheet
Anaerobic respiration
glucose → lactic acid (+energy released)
incomplete breakdown of glucose
Discuss the following questions in your pairs and then fill in your answers on your sheet.

Which types of athletic events require anaerobic respiration?

What is the downside to this form of respiration?
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Introduction to respiration
Station 1 – answer sheet
Anaerobic respiration occurs during high-intensity activities e.g. sprinting
If muscles are subjected to long periods of vigorous activity
they become fatigued, i.e. they stop contracting
efficiently. One cause of muscle fatigue is the build-up of
lactic acid in the muscles which causes cramps. Blood
flowing through the muscles removes the lactic acid.
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Introduction to respiration
Station 2 – information sheet
1
Yeast cells respire anaerobically producing ethanol and
carbon dioxide:
glucose → ethanol + carbon dioxide (+energy released)
Discuss the following questions in your pairs and then fill in your answers on your sheet.



This will eventually kill the yeast? Why?
What do we use the products of this type of respiration for?
Can you name other food products that utilise anaerobic respiration?
1
Yeast cells/ Credit: SciMAT / Photo Researchers / Universal Images Group/ Copyright © © Photo Researchers / For Education Use Only. This
and millions of other educational images are available through Britannica Image Quest. For a free trial, please
visit www.britannica.co.uk/trial
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Introduction to respiration
Station 2 – answer sheet
glucose → ethanol + CO (+ energy released)
2
Yeast cells respire anaerobically – eventually the ethanol build-up will
become toxic to the yeast.

Ethanol is used to make alcoholic drinks

CO is used to make bread rise

All of these food products utilise anaerobic respiration – yoghurt, cheese, vinegar
2
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Introduction to respiration
Station 3 – information sheet
Where enzymes are made.
Location of reactions in
anaerobic respiration
Holds genetic code for
enzymes involved in
respiration
Contains the enzymes for
aerobic respiration.
Allows gases and water to
pass freely into and out of
the cell. Controls the
passage of other molecules.

Name the structures used in respiration in plant and animal cells.
Station 3 – answer sheet

Most of the reactions in aerobic respiration take place inside mitochondria.
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Introduction to respiration
Station 4 – information sheet
Anaerobic respiration is essential for short bursts of energy but cannot be used for
longer periods. Endurance athletes need to pace themselves to avoid anaerobic
respiration. A build-up of lactic acid would hinder their performance.

Jude should keep her heart rate just below the lactic acid threshold (the point
where her blood lactic acid conc. starts to rise) when she trains.
What should her maximum heart rate be?
Station 4 – answer sheet
Maximum heart rate should be somewhere between 155 and 165 beats per minute.
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Introduction to respiration
Station 5

During an aerobics class, what would happen to your body temperature, heart rate
and rate and depth of breathing? Why?
Aerobic respiration is a series of reactions which can summarised by this equation.
C6H12O6 + 6O2
glucose

→ 6CO2 + 6H2O (+ energy released)
oxygen
carbon dioxide
water
Does the above equation look familiar?
Station 5 – answer sheet

During an aerobics class, what would happen to your body temperature, heart rate
and rate and depth of breathing? Why?
They would all increase. These changes increase the blood flow to the muscles and so
increase the supply of sugar and oxygen and increase the rate of removal of carbon
dioxide. Heat is a by-product of respiration.
C6H12O6 + 6O2
glucose

oxygen
→ 6CO2 + 6H2O (+ energy released)
carbon dioxide
water
The equation for aerobic respiration (above) is the reverse of the equation for
photosynthesis (below).
6CO2 + 6H2O
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C6H12O6 +
6O2
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Introduction to respiration
Station 6
Hydrogencarbonate indicator is pink. It turns yellow if CO2 is added and purple if CO2 is
removed.
Discuss the following questions in your pairs and then fill in your answers on your sheet.



Predict the colour of the 4 tubes.
Why does the 3rd tube have foil around it?
What is the purpose of the 4th tube?
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Introduction to respiration
Station 6 – answers

Predict the colour of the 4 tubes – see below

Why does the pondweed tube have foil around it?
This prevents the pondweed from photosynthesising. Depending upon the rate of
photosynthesis vs. respiration the indicator could be pink, yellow or purple!

What is the purpose of the 4th tube?
Control
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Introduction to respiration
Station 7
Susan set up the apparatus as shown. Both sets of peas were sterilised to kill microbes
on their surfaces. She measured the temperature inside each flask every 12 hours. Her
results are shown in the table below, but she forgot to label her table.

Which results are for which flask? How do you know?
Temperature (°C)
Time (hours)
Flask?
Flask?
0
15
15
12
15
20
24
15
25
36
15
29
48
15
31
60
15
33
72
15
33
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Introduction to respiration
Station 7 – answer sheet
Temperature (°C)
Time (hours)

Flask B
Boiled peas
Flask A
Peas soaked in water
0
15
15
12
15
20
24
15
25
36
15
29
48
15
31
60
15
33
72
15
33
The peas are in flask A respiring and respiration produces heat. The peas in flask
B were dead (had been boiled) so could not respire and release heat energy.
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Introduction to respiration
Station 8
The test-tubes contain limewater which turns cloudy in the presence of CO 2
Breathe out gently into the straw.
Health and safety - DO NOT SUCK UP THROUGH THE STRAW.
You may need breathe out several times to cause a change.

What happens?

Does this show you are respiring aerobically or an anaerobically?
Health and safety - Remove the straw when you have finished to show the test tube
has been used.
Station 8 – answers

When you breathed into the limewater it should have turned cloudy – a positive
test for carbon dioxide.

The presence of CO2 in your exhaled air proves you are respiring aerobically.
C6H12O6 + 6O2
glucose
oxygen
→ 6CO2 + 6H2O (+ energy released)
carbon dioxide
water
Anaerobic respiration in animals – no carbon dioxide is produced.
glucose → lactic acid (+ energy released)
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