2.8 Cell Respiration
Essential idea: Cell respiration supplies
energy for the functions of life.
Energy in cells is all about the molecule shown, Adenosine
Triphosphate (ATP). The energy is held in the bonds
between atoms, in particular the high energy bond that
joins the second and third phosphates. ATP is the energy
currency of the cell. Hence the efficiency of respiration is
measured by the yield of ATP.
By Chris Paine
https://bioknowledgy.weebly.com/
http://commons.wikimedia.org/wiki/File:ATP_chemical_structure.png
Understandings, Applications and Skills
2.8.U1
2.8.U2
2.8.U3
2.8.U4
2.8.A1
2.8.A2
2.8.S1
Statement
Cell respiration is the controlled release of energy
from organic compounds to produce ATP.
Guidance
Details of the metabolic pathways of cell
respiration are not needed but the substrates
and final waste products should be known.
ATP from cell respiration is immediately available
as a source of energy in the cell.
Anaerobic cell respiration gives a small yield of ATP
from glucose.
Aerobic cell respiration requires oxygen and gives
a large yield of ATP from glucose.
Use of anaerobic cell respiration in yeasts to
produce ethanol and carbon dioxide in baking.
Lactate production in humans when anaerobic
respiration is used to maximize the power of
muscle contractions.
There are many simple respirometers which
Analysis of results from experiments involving
could be used. Students are expected to know
measurement of respiration rates in germinating
that an alkali is used to absorb CO2, so
seeds or invertebrates using a respirometer.
reductions in volume are due to oxygen use.
Temperature should be kept constant to avoid
volume changes due to temperature
fluctuations.
2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.
2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.
2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.
2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.
2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.
2.8.U2 ATP from cell respiration is immediately available as a source of energy in the cell.
2.8.U2 ATP from cell respiration is immediately available as a source of energy in the cell.
2.8.U2 ATP from cell respiration is immediately available as a source of energy in the cell.
2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.
This links to 2.5 Enzymes and 8.1 Metabolism (AHL)
2.8.U4 Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.
2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or
invertebrates using a respirometer.
The diagram shows the design of a typical respirometer.
They vary greatly in their design, but all can be used to
calculate the rate of respiration by measuring the
consumption of oxygen.
http://www.nuffieldfoundation.org/sites/default/files/PB_measuring-rate-of-metabolism-respirometer2-500.jpg
2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or
invertebrates using a respirometer.
The diagram shows the design of a typical respirometer.
They vary greatly in their design, but all can be used to
calculate the rate of respiration by measuring the
consumption of oxygen.
http://www.nuffieldfoundation.org/sites/default/files/PB_measuring-rate-of-metabolism-respirometer2-500.jpg
2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or
invertebrates using a respirometer.
The diagram shows the design of a typical respirometer.
They vary greatly in their design, but all can be used to
calculate the rate of respiration by measuring the
consumption of oxygen.
Filter paper
wicks
Aerobic respiration uses 6 molecules of gas (oxygen) and creates 6
molecules of gas (carbon dioxide) = no change in volume, but …
Increase the
efficiency of
carbon dioxide
absorption
Potassium
hydroxide
(alkali) solution
… carbon dioxide is absorbed therefore the
volume of gas in the respirometer decreases.
Respiring
organism
Suitable living
organism will
respire
aerobically
Hydroxide
solutions are used
to absorb carbon
dioxide in the air
http://www.nuffieldfoundation.org/sites/default/files/PB_measuring-rate-of-metabolism-respirometer2-500.jpg
2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or
invertebrates using a respirometer.
The diagram shows the design of a typical respirometer.
They vary greatly in their design, but all can be used to
calculate the rate of respiration by measuring the
consumption of oxygen.
Syringe
Used to reset the position of
the coloured oil
Capillary tube containing
coloured oil
Movement in the oil per
minute toward tube B
measures the rate of oxygen
consumption. If the diameter
of the capillary tube is known
then a volume can be
calculated
Rubber bungs seal tubes
Closes the system to prevent
changes in air volume not due
to respiration
Metal cage
Keeps the organism in place
and away from contact with
the hydroxide solution.
http://www.nuffieldfoundation.org/sites/default/files/PB_measuring-rate-of-metabolism-respirometer2-500.jpg
2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or
invertebrates using a respirometer.
The diagram shows the design of a typical respirometer.
They vary greatly in their design, but all can be used to
calculate the rate of respiration by measuring the
consumption of oxygen.
Hoffman clip
Seals the
respirometer and
can be opened to
reset it after the
volume has been
reduced by
oxygen
consumption.
Temperature
controlled
n.b. due to gas expansion the
Hoffman clip should be left open
until the respirometer is at the
desired temperature – if not an
explosion can result.
The
respirometer is
immersed in a
water bath to
prevent
temperature
affecting the
pressure and
hence volume of
air in the
apparatus.
http://www.nuffieldfoundation.org/sites/default/files/PB_measuring-rate-of-metabolism-respirometer2-500.jpg
2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or
invertebrates using a respirometer.
The diagram shows the design of a typical respirometer.
They vary greatly in their design, but all can be used to
calculate the rate of respiration by measuring the
consumption of oxygen.
Tube A
Acts as a control
to ensure that
changes in the
level of coloured
oil are due to
respiration, not
the reaction of
the akali with
atmospheric
gases other
than carbon
dioxide.
http://www.nuffieldfoundation.org/sites/default/files/PB_measuring-rate-of-metabolism-respirometer2-500.jpg
Nature of Science: assessing the ethics of scientific research - the use of invertebrates in respirometer experiments has
ethical implications. (4.5)
The diagram shows the design of a typical respirometer.
They vary greatly in their design, but all can be used to
calculate the rate of respiration by measuring the
consumption of oxygen.
Respiring organism: If using invertebrates rather than
seeds what are the ethical questions that need answering?
http://www.nuffieldfoundation.org/sites/default/files/PB_measuring-rate-of-metabolism-respirometer2-500.jpg
Nature of Science: assessing the ethics of scientific research - the use of invertebrates in respirometer experiments has
ethical implications. (4.5)
The diagram shows the design of a typical respirometer.
They vary greatly in their design, but all can be used to
calculate the rate of respiration by measuring the
consumption of oxygen.
Respiring organism: If using invertebrates rather than
seeds what are the ethical questions that need answering?
•
•
•
•
Is it acceptable to remove animals from their natural habitat for use in an experiment?
Can the animals be safely returned to their habitat?
Will the animals suffer pain or any other harm during the experiment?
Can the risk of accidents that cause pain or suffering to the animals be minimized during
the experiment? In particular, can contact with the alkali be prevented?
• Is the use of animals in the experiment essential or is there an alternative method that
avoids using animals?
http://www.nuffieldfoundation.org/sites/default/files/PB_measuring-rate-of-metabolism-respirometer2-500.jpg
2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or
invertebrates using a respirometer.
The diagram shows the design of a typical respirometer.
They vary greatly in their design, but all can be used to
calculate the rate of respiration by measuring the
consumption of oxygen.
You should aim to carry out your own investigation
In the absence of equipment you can use the worksheet (Q1-10) with the virtual lab:
http://biologycorner.com/worksheets/cellular_respiration_AP_Lab5_virtual.html
http://www.nuffieldfoundation.org/sites/default/files/PB_measuring-rate-of-metabolism-respirometer2-500.jpg
2.8.U3 Anaerobic cell respiration gives a small yield of ATP from glucose.
2.8.U3 Anaerobic cell respiration gives a small yield of ATP from glucose.
2.8.A1 Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.
Bread is made by adding water to flour, kneading the mixture to make dough and
then baking it. Usually an ingredient is added to the dough to create bubbles of gas,
so that the baked bread has a lighter texture (e.g. yeast).
After kneading (mixing) the dough is kept
warm to encourage the yeast to respire.
Yeast can respire aerobically or anaerobically, but oxygen in the dough is
soon used up so the yeast is forced to respire anaerobically.
The carbon dioxide produced by anaerobic cell respiration cannot escape
from the dough and forms bubbles causing the dough to swell and rise.
Ethanol is also produced by anaerobic cell
respiration, but it evaporates during baking.
http://commons.wikimedia.org/wiki/File:Frenchbread3000ppx.jpg
2.8.A1 Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.
Bioethanol (ethanol produced by organisms)
is a renewable energy source.
Most bioethanol is produced from sugar cane
and maize, using yeast.
Starch and cellulose in the plant material are
broken down by enzymes into sugars.
http://en.wikipedia.org/wiki/File:Ethanol_plant.jpg
Fermenters are used to keep the yeast in optimum conditions.
When yeast carry out anaerobic respiration
the sugars in the plant material are converted
to ethanol and carbon dioxide.
The ethanol produced by the yeasts is
purified by distillation and water is
removed to improve combustion.
http://en.wikipedia.org/wiki/File:Saab_93_SportCombi_1.8t_BioPower_Facelift_rear.JPG
http://commons.wikimedia.org/wiki/File:Cornfield_in_South_Africa2.jpg
2.8.A2 Lactate production in humans when anaerobic respiration is used to maximize the power of muscle
contractions.
Certain human activities require anaerobic respiration
such as weightlifting and sprinting.
Aerobic respiration generates a much greater yield
of ATP, but anaerobic respiration can supply ATP
very rapidly, as oxygen is not required.
Rapid generation of ATP enables us to
maximise the power of muscle contractions.
Anaerobic cell respiration produces lactate. There is a limit to
the concentration that the body can tolerate and this limits how
much or how long anaerobic respiration can be done for.
Afterwards lactate must be broken down. This involves the use of
oxygen. It can take several minutes for enough oxygen to be absorbed
for all lactate to be broken down. The demand for oxygen that builds
up during a period of anaerobic respiration is called the oxygen debt.
http://commons.wikimedia.org/wiki/File:Osaka07_D2A_Torri_Edwards.jpg
Bibliography / Acknowledgments
Jason de Nys