RESPIRATION - aerobic respiration and anaerobic respiration in plants, fungi and animals - oxygen debt and build-up of lactic acid

Doc Brown's Biology Revision Notes

Suitable for GCSE/IGCSE/O level Biology/Science courses or equivalent

 Respiration is the process of releasing energy from digested food- therefore respiration is an exothermic process.

 Respiration transfers energy that cell needs to fully function.

 'Aerobic' means 'with oxygen' (usually in reference to respiration).

 'Anaerobic' means 'without oxygen' (usually refers to respiration).

 Know and understand that respiration in cells can take place aerobically or anaerobically depending on conditions and whether the cell is in an animal, plant, fungi or bacteria.

 Know and understand that the energy released in respiration is used in a variety of ways.

 Know that the human body needs to react to the increased demand for energy during exercise.

You should be able to use your skills, knowledge and understanding to interpret the data relating to the effects of exercise on the human body.

See also Keeping healthy - diet and exercise  gcse biology revision notes



Introduction to respiration and its significance

Do NOT think respiration is breathing in and out.

Respiration is the process of transferring chemical energy to power the chemistry of ALL cells by breaking down sugars like glucose - aerobically with oxygen or anaerobically without oxygen and overall the process is exothermic - energy releasing.

Respiration chemistry is very complex involving many reactions.

Respiration occurs in both plants animals and must be continuously happening to keep the organism alive!

Glucose, under the right conditions, can be completely oxidised to carbon dioxide and water.

This is analogous to burning a fuel in a combustion reaction - but a lot slower and no flame!

Organisms cannot survive without the energy from respiration and this process must go on continuously in every cell in any living organism.

An organism's cells cannot use the energy directly, but a molecule called ATP (adenosine triphosphate) is made and acts as a secondary chemical potential energy store.

The ATP molecule can then power all the essential chemistry e.g. breaking down or synthesising molecules in an organism's metabolism (*), facilitating active transport, organ function including the working of the muscles. (* Metabolism is all the chemical reactions in an organism)

Overall cellular respiration must be exothermic, otherwise there would be no net energy release! So, eventually, there is a net transfer of energy to the environment.

A typical person might average a power output of over 50 J/s, about the same as a 50 W light bulb!

All the chemistry of respiration is catalysed by the specific enzymes in cells.

The rate of respiration is affected by the ambient temperature, pH and the concentration of e.g. sugars and oxygen.

Note that these are the three factors which affect efficiency of enzyme controlled reactions.

The substrate molecules required for respiration are usually sugars like glucose, but the products of respiration depend on conditions e.g. oxygenated environment or lack of oxygen and whether the cells are animal, plant, fungi or bacteria.

Apart from glucose, other carbohydrates - sugars, proteins and fatty acids from lipids can be consumed in respiration.

This page compares the processes of aerobic respiration and anaerobic respiration - in plants/fungi and animals and considers the different conditions, substrates, products and relative yields of ATP for the different respiration situations.

You should understand that respiration in cells can take place all the time aerobically or anaerobically.

You should know and understand that the energy released in respiration is used in a variety of ways e.g.

to build larger molecules from smaller ones eg proteins from amino acids (plants and animals), starch from glucose (plants), cellulose from glucose (plants).

in plants and animals are made from glycerol and three long chain fatty acid molecules

in animals, to enable muscles to contract and relax eg to move limbs and move around,

in mammals and birds, to maintain a steady body temperature in colder surroundings, we slowly cease to function if we get to hot or too cold.

Also appreciate that the human body needs to react to any increased demand for energy during exercise.

So more glucose will be broken down in respiration.

in plants, sugars, nitrates and other nutrients, amino acids are then built up into proteins - animals can't do this, we need to take in protein, break it down and rebuild them up to our required proteins.

in animals excess protein is broken down to urea, a waste product excreted in urine.

All of these examples are part of the metabolism chemistry of an organism.

See Enzymes - structure and functions notes for examples of metabolic chemistry

Sources of substrate molecules for respiration

Plants are producers and make their own glucose for respiration from photosynthesis.

Animals are consumers and have to produce glucose by breaking down the biomass of the organisms-food that they eat.

There are two types of respiration - aerobic (with plenty of oxygen) and anaerobic (with little, if any, oxygen)

TOP OF PAGE


Aerobic respiration in animals

Aerobic respiration needs the sugar from digesting carbohydrates and oxygen via air breathed in by the organism, and from the lungs carried round the body by specialised red blood cells in the case of many animals.

You need plenty of oxygen for aerobic respiration - oxygenated conditions from free dissolved oxygen gas.

Most of the reactions of aerobic respiration in eukaryotes (plant or animal) take place inside the sub-cellular structures called the mitochondria of cells. Mitochondria contain all the enzymes needed for respiration.

In microorganisms like bacteria, prokaryotic cells, the aerobic respiration chemistry occurs in the cytoplasm.

glucose  + oxygen ===>  carbon dioxide  +  water  + energy

C6H12O6(aq)  +  6O2(g)  ===>  6CO2(g)  +  6H2O(l)  +  energy

The glucose is eventually completely oxidised to the waste products - carbon dioxide and water - but via lots of complicated chemical reactions and producing 32 molecules of ATP per molecule of glucose!

Most of the time, you are using this type of aerobic respiration and the simple experiment (illustrated on the right) shows a simple limewater test for the presence of carbon dioxide in the air you breathe out - the presence of carbon dioxide is shown by the appearance of a white precipitate ('milkyness').

The actual energy release takes place through a very complex biochemistry cycle involving ADP (adenosine diphosphate) and its conversion to ATP (adenosine triphosphate) which is the molecule that actually supplies the energy to power most of the chemistry of any cell.

The more ATP that is made, the greater the supply of energy available.

Aerobic respiration can make 32 molecules of ATP per molecules of glucose.

 Know and understand the chemical reactions inside cells are controlled by enzymes.

Your body, hence your enzyme systems, will respond to its needs e.g. when you use muscles in doing physical work or exercise.

Know and understand during aerobic respiration (respiration that uses oxygen) chemical reactions occur that:

produce useful energy is released to 'power' the cell chemistry.

Know and understand that aerobic respiration takes place continuously in both plants and animals.

Know and understand that energy that is released during respiration is used by the organism.

Know that the energy may be used in cells:

to build larger molecules from smaller ones eg proteins from amino acids,

in animals, to enable muscles to contract and relax eg to move limbs and move around,

in mammals and birds, to maintain a steady body temperature in colder surroundings, we slowly cease to function if we get to hot or too cold.

in plants, to build up from sugars, nitrates and other nutrients, amino acids which are then built up into proteins - animals can't do this, we need to take in protein, break it down and build it up to our required proteins.

Know and understand that during exercise a number of changes take place in your body:

the more you use your muscles, the more oxygen you need for respiration

the heart rate increases, the more so, the more vigorous the exercise, and even more oxygen and glucose are needed

the rate and depth of breathing increases, to increase oxygen intake.

Know and understand that these changes increase the blood flow to the muscles and so increase the supply of sugar and oxygen for energy from respiration and also increase the rate of removal of carbon dioxide - the waste product.

Know and understand that muscles store glucose as glycogen, which can then be converted back to glucose for use during exercise.

Glycogen is produced, stored and then released for conversion to glucose on a supply and demand basis.

If there is surplus glucose and physical activity is low, more glycogen is produced.

The more you physically exercise, the greater the glucose demand, if this exceeds what is available in the blood stream, then the glycogen reserves are called upon to fill the energy gap.

 

Summary of important points on aerobic respiration

Be able to explain why heart rate and breathing rate increase with exercise.

All chemical reactions inside cells are controlled by enzymes.

Your body, hence your enzyme systems, will respond to its needs e.g. when you use muscles in doing physical work or exercise.

As stated, during aerobic respiration (respiration that uses oxygen) chemical reactions occur that use glucose (a sugar) and oxygen

The sugar is from digesting carbohydrates and oxygen in via air breathed in, and from the lungs carried round the body by specialised red blood cells,

Respiration produces useful energy is released to 'power' the cell chemistry.

During exercise a number of changes take place in your body.

The more you use your muscles, the more oxygen you need for respiration

The heart rate increases, the more so, the more vigorous the exercise, and even more oxygen and glucose are need, so the rate and depth of breathing increases, to increase oxygen intake.

Measuring your pulse rate - a simple measure of your rate of respiration

You can measure your pulse rate quite easily e.g. put two fingers on the back of your wrist and time the number of pulses in a minute e.g. with a digital stopwatch or your iphone app etc.

You can do this as a simple homework exercise!

OR as a class exercise on a fine day, or any day in the gym, and average the class results giving a wider range of people and more accurate data set.

Wear appropriate footwear and make sure all the class do the same exercise!

Record your pulse rate after do the following sorts of exercise for 5 minutes at a time:

1. sitting quietly;  2. walking at your normal pace;  3. slow jogging;  4. running

For greater statistical accuracy ('best value') you should repeat the experiment several times to get four average pulse rates.

After allowing extra rest time between each activity, you should find your pulse rate increases from 1. to 4. because your rate of respiration is increasing and you need an increase in the rate of transfer of oxygen to your cells and simultaneously remove carbon dioxide too.

More vigorous the exercise changes increases your heart rate, hence the blood flow to the muscles and to increase the supply of sugar and oxygen for energy from respiration and also increase the rate of removal of carbon dioxide - the waste product. Your breathing (ventilation) rate increases to meet the increased demands of the aerobic respiration rate.

Aerobic respiration takes place continuously in both plants and animals and most of the reactions in aerobic respiration take place inside the mitochondria of cells.

 

TOP OF PAGE


Aerobic respiration in plants and fungi

 As above for animals.

In green plants, in daylight the rate of photosynthesis will exceed that of respiration, but at night or very low light levels, the rate of respiration will exceed that of photosynthesis, otherwise the plant would die! At dusk or dawn, in poor light, the rates of photosynthesis and respiration are similar.

You can use a plant example to show heat energy is released in respiration (aerobic or anaerobic in living organisms).

Such an experiment to show germinating peas or beans release energy using aerobic respiration is illustrated (right diagram).

One lot of peas/beans is soaked for at least 24 hours to get them germinating - look for little shoots/sprouts. Another lot are boiled to kill the enzymes that catalyse respiration - effectively killing the peas/beans. (the 'control' for a fair test).

Each lot is placed in a thermos flask (vacuum flask) on top of some moist cotton wool - space ifs left for an air supply to the peas/beans.

A thermometer is placed in each flask and the neck sealed with a cotton wool plug - both flasks should be kept under the same laboratory conditions of temperature for a week..

Any heat released will produce a temperature rise. If you record the temperature every day you should find that the flask of germinating peas/beans will show an increase in temperature - from heat energy release by respiration.

The control flask of boiled peas/beans should not show a temperature rise.

You can do a similar experiment with the boiled (dead) and unboiled (germinated by soaking for 24 hours) peas or beans to show the formation of carbon dioxide (aerobic or anaerobic) in respiring living organisms). - the simple experiment is illustrated below using germinating peas or beans and dead peas/beans.

Carbon dioxide is a slightly acidic gas. If carbon dioxide dissolves in the red hydrogencarbonate indicator solution, it turns it yellow. The indicator solution contains a dissolved salt, sodium hydrogencarbonate, and a coloured pH indicator that you see in your chemistry lessons - the carbon dioxoide lowers the pH of water.

The peas/beans are suspended on a gauze or layer of cotton wool above some hydrogencarbonate indicator solution in boiling tubes - the boiling tubes are sealed with bungs to stop carbon dioxide from the air getting in

You leave the pair of boiling tubes for an hour.

Left: The germinating peas/beans are respiring and give off carbon dioxide turning the indicator solution yellow.

Right: In the control boiling tube, the dead peas/beans cannot respire (enzymes dead) and you see no change in the indicator colour because no carbon dioxide was formed.

You can do this experiment with animals like woodlice or maggots, using glass beads in the control tube - NOT dead animals and the living animals should not be kept for too long to run out of oxygen and die - ethical points.

You can compare the rates of respiration for different animals but its a pretty crude experiment - I suppose you could weigh equal masses of the animal into the boiling tubes.


Anaerobic respiration in animals

When doing vigorous exercise your body cannot supply enough oxygen to your muscles for 100% aerobic respiration.

If there is a lack of oxygen ('anaerobic' means 'without oxygen') you cannot oxidise the glucose sugar completely, as in the case of aerobic respiration - the greatly simplified equation for the incomplete breakdown of glucose is:

glucose  ===>  lactic acid  +  energy

C6H12O6   ===>  2C3H6O3  +  energy

(structure of lactic acid is CH3CH(OH)COOH, a carboxylic acid with an alcohol group)

This anaerobic reaction only partially breaks down the glucose to lactic acid in animals and some bacteria.

Note

(i) The waste product is lactic acid, not carbon dioxide and water.

(ii) The products are different in plants and some microorganisms (see next section).

This is not as efficient as aerobic respiration and considerably less ATP is formed, reducing the potential energy supply.

You only make two molecules of ATP per molecule of glucose.

A much less efficient process of transferring energy from the glucose chemical energy store.

Anaerobic respiration takes place in the cytoplasm plant and animal cells and some microorganism e.g.

(a) In human cells, when you do vigorous exercise, you body can't supply enough oxygen, so the cells use anaerobic respiration too.

(b) If plant root cells are growing in waterlogged ground, there is little oxygen available, so they must respire aerobically.

(c) If bacteria cells get under your skin where there is little oxygen, they can still survive by using anaerobic respiration.

In animals, if the physical activity is intense and prolonged you get the 'cramps' pains due to the build up of lactic acid, which can be painful as anaerobic respiration kicks in due to lack of oxygen. With anaerobic respiration you do get the build up of lactic acid in the muscles because it is more difficult to oxidise and release energy.

This is not as efficient in energy release as the complete aerobic respiration of glucose described above, but it does enable you to keep your muscles going for longer. Anaerobic respiration produces a build up of lactic acid in the muscles which can be painful e.g. you suffer from 'cramps'.

However, anaerobic respiration has the advantage of enabling the body to keep going for a limited time, even if you are a bit short of oxygen!

This can be important in an emergency situation when you need to use your muscles more than you intended.

 

Know and understand anaerobic respiration results in an oxygen debt that has to be repaid in order to oxidise lactic acid to carbon dioxide and water.

Know and understand that if muscles are subjected to long periods of vigorous activity they become fatigued, ie they stop contracting efficiently.

The more vigorous the exercise, the more energy you need and you need to increase your rate of respiration.

You need to breathe at a faster rate and take in larger volumes of air for the oxygen needed to sustain this increase in rate of respiration.

Your heart rate increases to get the oxygenated blood to your muscles and simultaneously remove the carbon dioxide efficiently too.

When your exercise is really vigorous there is not enough oxygen for aerobic respiration so your body responds by using anaerobic respiration too.

However, anaerobic respiration is not as energy efficient in transferring energy as aerobic respiration and if the exercise is prolonged you become fatigued.

Know that one cause of muscle fatigue is the build-up of lactic acid in the muscles from anaerobic respiration even though the blood flowing through the muscles removes the lactic acid, oxygen is used up to oxidise lactic acid to carbon dioxide and water.

 


More on oxygen debt an the build-up of lactic acid

During vigorous exercise the heart, lungs and limb muscles begin struggle to keep up with what you want your body wants to do (fatigue), but you can keep your muscles going longer using anaerobic respiration, at least up to a point of total fatigue - like just about staggering over the line at the end of a marathon!

Unfortunately, when your body starts to use anaerobic respiration, you are building up an 'oxygen debt'.

An oxygen debt is the quantity of oxygen your body needs to react with the build up of lactic acid in the cells and remove it by oxidation to carbon dioxide and water (as happens with aerobic respiration of glucose).

This means your body has to be repaid with the oxygen that the muscles didn't get for complete aerobic respiration - your lungs, heart rate and bloodstream couldn't keep up with demands of aerobic respiration.

This means, even when you stop doing a vigorous exercise, you have to continue to breathe quite deeply to repay this oxygen debt, transfer oxygen to the cells and oxidise the lactic acid in them to the harmless waste products of carbon dioxide and water.

As long as your body detects higher than normal levels of carbon dioxide or lactic acid your breathing rate and pulse rate will stay higher than normal until their levels are reduced to normal, i.e. when all the excess lactic acid has been oxidised to carbon dioxide and water.

Note: Your body does have another way of reducing high levels of lactic acid and carbon dioxide. The blood flow through your muscles transports lactic acid to the liver where it is converted back to glucose - chemically the opposite reaction to anaerobic respiration.

 

See also Keeping healthy - diet and exercise  gcse biology revision notes

 


Anaerobic respiration in plants and fungi

Plants respire aerobically, but also anaerobically too.

Again, as in the case of animals, if there is a lack of oxygen ('anaerobic conditions'), you cannot oxidise the glucose sugar completely, as in the case of aerobic respiration, but in plants and yeast cells the product isn't lactic acid, but ethanol ('alcohol') and carbon dioxide!

An example of this in plants is fermentation in yeast cells (a single celled organism classed as a type of fungi), the reaction being

glucose ===> ethanol ('alcohol')  +  carbon dioxide  +  energy

C6H12O6(aq) ====> 2C2H5OH(aq) + 2CO2(g)  + energy

The ethanol ('alcohol') is a by-product of the respiration process.

Again, this is not as efficient as aerobic respiration and less ATP is formed, reducing the potential energy supply.

Notes: Fermentation in bacteria produces lactic acid, the same as anaerobic respiration in animals.

Fermentation using yeast is widely used in the food and drinks industry.

Yeast is used in baking products like bread, where the evolution of the carbon dioxide gives the 'rising' action.

Yeast fermentation of sugar is used to make alcoholic drinks like beers and wines. The fermentation reaction makes the 'alcohol' (ethanol, C2H5OH) and the dissolved carbon dioxide gas makes the 'fizz' or 'froth'.

Under certain conditions plants have to switch from aerobic respiration to anaerobic respiration

e.g. circumstances when there is little oxygen in the immediate environment.

 Underground, root cells respire anaerobically, if the plants are growing in water logged soil conditions.

 


A comparison of aerobic respiration and anaerobic respiration in plants and animals

In prokaryotic organisms, aerobic respiration takes place in the cytoplasm.

In eukaryotic organisms, aerobic respiration takes place in the mitochondria of cells.

Anaerobic respiration takes place in the cytoplasm plant cells, animal cells and some microorganisms.

Similarities and differences Aerobic respiration Anaerobic respiration
Conditions Plenty of oxygen present e.g. normal exercise. Little oxygen present due to e.g. vigorous exercise in an animal or organisms in waterlogged soils.
Substrate inputs Glucose or other sugar or any organic molecule like a fatty acid or protein molecule that can be completely oxidised. Glucose or other sugar or any organic molecule like a fatty acid or protein molecule that can be partially oxidised.
Product outputs Carbon dioxide and water. In animals and some bacteria it is lactic acid. In plants, and some microorganisms like yeast, the products are ethanol and carbon dioxide.
ATP yield High e.g. 30 to 38 ATP molecules per molecule of glucose. Low e.g. 2 ATP molecules per molecule of glucose (15-19 x less than with aerobic respiration).

 


Investigating the anaerobic respiration rate of yeast

You can investigate the rate of anaerobic respiration of yeast cells using a sugar substrate.

 

The chemistry of the anaerobic respiration of yeast cells

If you start with sucrose, the enzyme invertase hydrolyses sucrose and breaks it down into glucose and fructose.

sucrose  +  water  == enzyme invertase ==> glucose + fructose

C12H22O11  +  H2O  ===> C6H12O6  +  C6H12O6 

The actual anaerobic fermentation reaction is ...

glucose/fructose (sugar) == enzyme zymase ==> ethanol + carbon dioxide

C6H12O6(aq) ===> 2C2H5OH(aq) + 2CO2(g) 

You can following the speed of the reaction by measuring the volume of carbon dioxide formed.

 

Experimental procedure and analysis of results

Using a thermostated bath you can investigate the effect of temperature on fermentation.

You must keep the concentration of the sugar plus yeast mixture constant - fixed volumes of previously prepared stock solutions of the sugar or yeast suspension.

You can start at 20oC and repeat the experiments several times for each temperature, and then raise the temperature by 5oC at a time to see the effect.

You can measure the rate of respiration in terms of the rate of evolution of gas e.g. cm3 CO2/min.

Using the above apparatus, or that described below (gas syringe) you can the rate of respiration with different substrates AND, for a fixed substrate, the effect of changing its concentration at constant temperature and constant enzyme concentration.

Note:

If you bubble the gas from the reaction mixture through a limewater you get a white precipitate ('milkyness'), a positive test for carbon dioxide from the yeast anaerobic respiration..

You get exactly the same result if you blow some of your expelled breath through limewater - the same carbon dioxide from your aerobic respiration.

-

You can use a gas syringe system to make more accurate experiments.

Doing the experiments at constant room temperature, you can keep the yeast concentration constant and vary the concentration of the sugar OR you can vary the substrate sugar (but keeping the sugar concentration constant).

(c) doc b

Typical graphical results you might obtain based on a rate of evolution of carbon dioxide e.g. cm3 CO2/minute.

 

See also ENZYMES - structure, function, optimum conditions, investigation experiments  gcse biology revision notes

See also Enzymes and Biotechnology (gcse chemistry notes)


An experiment to measure the rate of aerobic respiration of woodlice using a respirometer

This describes how to investigate the rate of respiration of small organisms like woodlice by measuring their rate of uptake of oxygen that is being used in the organisms metabolism.

A respirometer is a device designed to measure the rate of consumption of oxygen by a living organism.

The rate of oxygen depletion in the air e.g. cm3/min by gas volume or mm/min on some scale is taken as a measure of the rate of respiration.

You can also use germinating peas or germinating beans to investigate the effect of temperature on the rate of their respiration.

 

The experimental set up - a respirometer system

A boiling tube is set up in a thermostated water bath to control the temperature of the experiment - you should use a thermometer to accurately monitor the temperature of the water. A syringe containing air and a manometer are connected via glass tubing through a rubber bung to the boiling tube. Together with the soda lime this set up is called a respirometer.

A manometer is a device to measure pressures. A common simple manometer consists of a U shaped tube of glass filled with some liquid - in this case coloured water NOT poisonous mercury! A ruler scale is placed in between the arms of the U tube so the height of the liquid can be measured in both arms.

The syringe is used to set the level of the liquid in the manometer.

At the bottom of the boiling tube soda lime granules are placed to absorb carbon dioxide given out by the respiring woodlice. On top of the soda lime is a wad of cotton wool to prevent contact with the woodlice - they would be harmed by the strongly alkaline soda lime - an ethical point when using live animals in experiments.

The live woodlice are carefully placed on the cotton wool and the rest of the apparatus of the respirometer is carefully assembled so that boiling tube is vertical in the water bath.

Note: The reduction in volume shows a gas is being removed from air, and that gas is oxygen.
 

Investigation procedure

(a) The water bath, and boiling tube without woodlice in the boiling tube, are left for a short time until the temperature of the water bath has settled down to your desired start temperature e.g. 15 or 20oC.

(b) The woodlice are then quickly placed in the boiling tube, connect everything up as shown in the diagram.

(c) The siring is used to equate the liquid levels in the manometer, preferably to zero difference in height (R1 = 0).

(d) Let the woodlice respire for a fixed time. As they respire and use up oxygen, carbon dioxide is produced, which is absorbed by the soda lime, decreasing the volume of air.

(e) As the air volume decreases, it temporarily reduces the pressure in the boiling tube, therefore, to maintain the constant external pressure ('fair test'), the liquid moves up the left limb of the U tube manometer.

(f) After a set time, you read the two levels to determine R2 (left reading - right reading in the U tube).

The total distance moved by the liquid = the difference between the two readings, R2 - R1, and this gives you a relative measure of the rate of respiration.

(technically it doesn't matter if R1 isn't zero at the start, as long as you subtract the initial differential reading R1 from R2, you obtain the actual numerical change desired.)

(g) You then repeat (a) to (f) with the same woodlice, at a higher temperatures going up 5o at time up to 50oC.

Experimental note:

Theoretically, because the siring is also calibrated, the siring 'plunger' can be carefully depressed to return the manometer liquid levels to their original readings.

The volume of oxygen used = final syringe volume - initial syringe volume (e.g. in cm3).

This allows you to calculate the woodlice rate of respiration in cm3/min.

Ethical note:

The woodlice should not be used at sufficiently high temperatures that they die.

The woodlice should not be left in the respirometer too long so that they run out of oxygen and die.

After the experiment they should be released back into their natural outside habitat.

 

Results, analysis and conclusions

As described above, the relative rate of respiration is measured as the rate of oxygen consumption in mm/min or cm3/min.

(c) doc bYou can then plot a graph of rate of respiration versus temperature.

You should find initially the rates increases, passes through an optimum at ~35-40oC and then decreases. steadily as the temperature goes higher.

This is typical of the behaviour of enzyme controlled reactions - which includes the metabolic chemistry of respiration.

 


Your practical work to develop your skills and understanding may have included the following:

Investigating the rate of respiration in yeast using carbon dioxide sensors and dataloggers (see above).

Investigating the effect of exercise on pulse rate, either physically or using pulse sensors and dataloggers,

Breathing rate can be measured by counting your breaths per minute.

Your heart rate can be measured by taking your pulse rate (heart rate in beats/minute)

You can measure your normal steady breathing rate and pulse rate.

Then do some vigorous exercise for a e.g. 5 minutes.

Then rest and re-measure your breathing rate and pulse rate at regular time intervals for say 10 or 15 minutes.

This allows you to see your body slowly recovering back to 'normal'.

You should see dramatic increases in your breathing rate and pulse rate after doing some vigorous exercise.

You can compare sitting, light walking, jogging and running, the resulting numerical trend in breathing/pulse rates should pretty well much as expected, but note that after very vigorous running, the oxygen debt might kick in and may take some time for your breathing/pulse rates to return to normal.

Investigating the link between exercise and breathing rate with a breathing sensor,

Investigating holding masses at armís length and timing how long it takes the muscles to fatigue,

Designing an investigation using force meters and dataloggers to find the relationship between the amount of force exerted by a muscle and muscle fatigue.

TOP OF PAGE


Typical learning objectives for respiration

Know that respiration is a process used by all living organisms that releases the energy in organic molecules.

The organic molecules used in respiration are usually sugars.

Respiration goes on in all living cells

The energy may is used in cells:

to build larger molecules from smaller ones eg proteins from amino acids,

in animals, to enable muscles to contract and relax eg to move limbs and move around,

in mammals and birds, to maintain a steady body temperature in colder surroundings, we slowly cease to function if we get to hot or too cold.

in plants, to build up from sugars, nitrates and other nutrients, amino acids which are then built up into proteins - animals can't do this, we need to take in protein, break it down and build it up to our required proteins, all of which needs energy.

Be able to explain how the human circulatory system facilitates respiration, including:

(a) glucose and oxygen diffuse from capillaries into respiring cells

(b) carbon dioxide diffuses from respiring cells into capillaries.

The circulatory system carries all the glucose, oxygen, waste carbon dioxide (and everything else) around all the body via the blood stream.

The glucose comes from digestive breakdown of foods like carbohydrates.

By breathing in, we obtain oxygen from the air, and the waste carbon dioxide is expelled when we breath out.

All cells are near the thin blood capillaries which bring in the glucose (from gut) and oxygen (from lungs), that diffuse into the cells, and the waste carbon dioxide diffuses out to be transported to the lungs.

 


Typical learning objectives associated with respiration

Know that respiration is a process used by all living organisms that releases the energy in organic molecules.

The organic molecules used in respiration are usually sugars.

Respiration goes on in all living cells

The energy may is used in cells:

to build larger molecules from smaller ones eg proteins from amino acids,

in animals, to enable muscles to contract and relax eg to move limbs and move around,

in mammals and birds, to maintain a steady body temperature in colder surroundings, we slowly cease to function if we get      to hot or too cold.

in plants, to build up from sugars, nitrates and other nutrients, amino acids which are then built up into proteins - animals can't do this, we need to take in protein, break it down and build it up to our required proteins, all of which needs energy.

 

and for the associated page The human circulatory system - heart, lungs, blood, blood vessels

Be able to explain how the human circulatory system facilitates respiration, including

(a) glucose and oxygen diffuse from capillaries into respiring cells

(b) carbon dioxide diffuses from respiring cells into capillaries.

Know that:

The circulatory system carries all the glucose, oxygen, waste carbon dioxide (and everything else) around all the body via the blood stream.

The glucose comes from digestive breakdown of foods like carbohydrates.

By breathing in, we obtain oxygen from the air, and the waste carbon dioxide is expelled when we breath out.

All cells are near the thin blood capillaries which bring in the glucose (from gut) and oxygen (from lungs), that diffuse into the cells, and the waste carbon dioxide diffuses out to be transported to the lungs.

Be able to define diffusion as the movement of particles from an area of high concentration to an area of lower concentration.

Know how to apply this idea to the process of respiration.

The thin cell membranes allow the diffusion of small molecules in and out of cells.

Since the capillaries are thin and numerous, the diffusion distance from cells is short, so transfer of nutrients in, and waste products out, is as efficient as possible.

As the cells respire they use up oxygen/glucose, so their concentration falls in the cell. Therefore the external concentrations (e.g. in capillaries) is higher, so more oxygen/glucose will diffuse into the cell.

At the same time, the concentration of the waste product carbon dioxide builds in the cell, and so carbon dioxide will then naturally diffuse out of the cell to the lower concentration region in the capillaries.


Cell biology notes index (for all relevant GCSE biology pages)

See biology notes index - cell biology

and Keeping healthy - diet and exercise  gcse biology revision notes


IGCSE revision notes respiration KS4 biology Science notes on respiration GCSE biology guide notes on respiration for schools colleges academies science course tutors images pictures diagrams for respiration science revision notes on respiration for revising biology modules biology topics notes to help on understanding of respiration university courses in biological science careers in science biology jobs in the pharmaceutical industry biological laboratory assistant apprenticeships technical internships in biology USA US grade 8 grade 9 grade10 AQA GCSE 9-1 biology science GCSE notes on respiration Edexcel GCSE 9-1 biology science notes on respiration for OCR GCSE 9-1 21st century biology science OCR GCSE 9-1 Gateway  biology science notes WJEC gcse science CCEA/CEA gcse science

KS3 SCIENCE QUIZZES ALPHABETICAL INDEX
GCSE grade 9-1 & IGCSE CHEMISTRY Doc Brown's Travel Pictures & Notes
ADVANCED LEVEL CHEMISTRY [SEARCH BOX] - see below
GCSE 9-1 Physics Revision Notes GCSE 9-1 Biology Revision Notes
All website content © Dr Phil Brown 2000 onwards. All copyrights reserved on revision notes, images, quizzes, worksheets etc. Copying of website material is NOT permitted. Exam revision summaries and references to science course specifications are unofficial. Email doc b: chem55555@hotmail.com

 Doc Brown's Biology

*

 For latest updates see https://twitter.com/docbrownchem

 Have your say about doc b's website

TOP OF PAGE