2.8 Cell Respiration · produce ethanol and carbon dioxide in baking. 2.8.A2 Lactate production in...

Essential idea: Cell respiration supplies energy for the functions of life.

By Chris Paine

https://bioknowledgy.weebly.com/

2.8 Cell Respiration

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.

http://commons.wikimedia.org/wiki/File:ATP_chemical_structure.png

https://bioknowledgy.weebly.com/http://commons.wikimedia.org/wiki/File:ATP_chemical_structure.png

Understandings, Applications and Skills

Statement Guidance

2.8.U1 Cell respiration is the controlled release of energy

from organic compounds to produce ATP.

Details of the metabolic pathways of cell

respiration are not needed but the substrates

and final waste products should be known.

2.8.U2 ATP from cell respiration is immediately available

as a source of energy in the cell.

2.8.U3 Anaerobic cell respiration gives a small yield of ATP

from glucose.

2.8.U4 Aerobic cell respiration requires oxygen and gives

a large yield of ATP from glucose.

2.8.A1 Use of anaerobic cell respiration in yeasts to

produce ethanol and carbon dioxide in baking.

2.8.A2 Lactate production in humans when anaerobic

respiration is used to maximize the power of

muscle contractions.

2.8.S1 Analysis of results from experiments involving

measurement of respiration rates in germinating

seeds or invertebrates using a respirometer.

There are many simple respirometers which

could be used. Students are expected to know

that an alkali is used to absorb CO2, so

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.

http://i-biology.net/http://i-biology.net/

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.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.

Ethanol is also produced by anaerobic cell respiration, but it evaporates during baking.

http://commons.wikimedia.org/wiki/File:Frenchbread3000ppx.jpg

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.

http://commons.wikimedia.org/wiki/File:Frenchbread3000ppx.jpg

http://en.wikipedia.org/wiki/File:Ethanol_plant.jpg

http://en.wikipedia.org/wiki/File:Saab_9-3_SportCombi_1.8t_BioPower_Facelift_rear.JPG http://commons.wikimedia.org/wiki/File:Cornfield_in_South_Africa2.jpg

Bioethanol (ethanol produced by organisms) is a renewable energy source.

2.8.A1 Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.

Most bioethanol is produced from sugar cane and maize, using yeast.

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.

Starch and cellulose in the plant material are broken down by enzymes into sugars.

The ethanol produced by the yeasts is purified by distillation and water is removed to improve combustion.

http://en.wikipedia.org/wiki/File:Ethanol_plant.jpghttp://en.wikipedia.org/wiki/File:Saab_9-3_SportCombi_1.8t_BioPower_Facelift_rear.JPGhttp://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.

http://commons.wikimedia.org/wiki/File:Osaka07_D2A_Torri_Edwards.jpg

Certain human activities require anaerobic respirationsuch as weightlifting and sprinting.

Rapid generation of ATP enables us to maximise the power of muscle contractions.

Aerobic respiration generates a much greater yield of ATP, but anaerobic respiration can supply ATP very rapidly, as oxygen is not required.

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

2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or

invertebrates using a respirometer.

http://www.nuffieldfoundation.org/sites/default/files/PB_measuring-rate-of-metabolism-respirometer2-500.jpg

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.






Potassium hydroxide (alkali) solutionHydroxide solutions are used to absorb carbon dioxide in the air

Filter paper wicksIncrease the efficiency of carbon dioxide absorption

Aerobic respiration uses 6 molecules of gas (oxygen) and creates 6 molecules of gas (carbon dioxide) = no change in volume, but …

… carbon dioxide is absorbed therefore the

volume of gas in the respirometer decreases.Respiring organismSuitable living organism will respire aerobically






Capillary tube containing coloured oilMovement 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 tubesCloses the system to prevent changes in air volume not due to respiration

SyringeUsed to reset the position of the coloured oil

Metal cageKeeps the organism in place and away from contact with the hydroxide solution.






Temperature controlledThe respirometer is immersed in a water bath to prevent temperature affecting the pressure and hence volume of air in the apparatus.

Hoffman clipSeals the respirometer and can be opened to reset it after the volume has been reduced by oxygen consumption.

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.






Tube AActs 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.


Nature of Science: assessing the ethics of scientific research - the use of invertebrates in respirometer experiments has ethical implications. (4.5)



Respiring organism: If using invertebrates rather than seeds what are the ethical questions that need answering?


Nature of Science: assessing the ethics of scientific research - the use of invertebrates in respirometer experiments has ethical implications. (4.5)



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?






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.jpghttp://biologycorner.com/worksheets/cellular_respiration_AP_Lab5_virtual.html

Bibliography / Acknowledgments

Jason de Nys
http://ib.bioninja.com.au/http://ib.bioninja.com.au/http://i-biology.net/http://i-biology.net/http://www.slideshare.net/jasondenyshttp://www.slideshare.net/jasondenyshttp://www.slideshare.net/jasondenys

2.8 Cell Respiration · produce ethanol and carbon dioxide in baking. 2.8.A2 Lactate production in...

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