Teaching notes - Teachit Science · PDF fileTeaching notes This resource is the perfect introduction to respiration in which students discover aerobic and anaerobic respiration for

Introduction to respiration

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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



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

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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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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 → 6CO2 + 6H2O (+ energy released) glucose oxygen carbon dioxide water

Does the above equation look familiar – which other process does it remind you of?

…………………………………………………………………………………………………………………………………………

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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?

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What is the purpose of the 4th tube?

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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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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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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?



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.




1


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

Yeast cells respire anaerobically producing ethanol and carbon dioxide:

glucose → ethanol + carbon dioxide (+energy released)

http://www.britannica.co.uk/trial




glucose → ethanol + CO2 (+ energy released)

Yeast cells respire anaerobically – eventually the ethanol build-up will become toxic to the yeast.

Ethanol is used to make alcoholic drinks

CO2 is used to make bread rise

All of these food products utilise anaerobic respiration – yoghurt, cheese, vinegar




Name the structures used in respiration in plant and animal cells.


Most of the reactions in aerobic respiration take place inside mitochondria.

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.




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?


Maximum heart rate should be somewhere between 155 and 165 beats per minute.



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.


Does the above equation look familiar?


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.


The equation for aerobic respiration (above) is the reverse of the equation for

photosynthesis (below).

6CO2 + 6H2O light energy

C6H12O6 + 6O2



Station 6

Hydrogencarbonate indicator is pink. It turns yellow if CO2 is added and purple if CO2 is

removed.


Predict the colour of the 4 tubes.

Why does the 3rd tube have foil around it?




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!


Control



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?

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




Time (hours)

Temperature (°C)

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.



Station 8

The test-tubes contain limewater which turns cloudy in the presence of CO2

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.


Anaerobic respiration in animals – no carbon dioxide is produced.

glucose → lactic acid (+ energy released)

Teaching notes - Teachit Science · PDF fileTeaching notes This resource is the perfect introduction to respiration in which students discover aerobic and anaerobic respiration for

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