Aerobic Respiration - (GCSE Biology)

Aerobic Respiration

Respiration in Living Organisms

• Respiration releases energy through the production of ATP. Respiration is a chemical reaction in which living cells release energy from glucose (food) by producing ATP. The ATP provides energy for cells.
• Respiration is an exothermic reaction. This energy from respiration is released by living cells as heat energy. A reaction that gives out heat energy is known as an exothermic reaction.
• Respiration involves the action of enzymes in cells.

• Respiration is different to breathing. Breathing in and out supplies oxygen. Food or photosynthesis supplies glucose. Respiration uses these two to release energy.

Body Processes Require Energy

• Energy is required for body processes to take place. All the energy required for the running of an organism’s body is released by respiration. Energy is used for:

1. Building larger molecules – e.g. synthesising proteins from amino acids.
2. Movement – contraction of muscles to help us move.
3. Keeping warm – energy to maintain a constant body temperature .
4. Digestion – contraction of digestive muscles to digest food.
5. Breathing – contraction of intercostal muscles and diaphragm.
6. Other – cell division, active transport, growth, passage of nerve impulses and more – nearly every process in the body requires energy!

• Energy drives chemical reactions. The total of all chemical reactions in an organism, is known as metabolism.

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Aerobic Respiration

• Aerobic respiration requires oxygen. When organisms are taking in oxygen healthily, it is easy to respire and produce large amounts of energy. This is aerobic respiration.
• Aerobic respiration requires glucose. Aerobic respiration uses oxygen to react with glucose in order to produce carbon dioxide and water whilst producing energy (through the creation of ATP). This reaction can be represented by an equation:

Chemical Equation of Aerobic Respiration

The chemical reaction occurring in aerobic respiration can also be represented in chemical symbols:

Investigating Respiration

Rates of Respiration

You can investigate the effect of temperature on the rate of respiration by measuring the uptake of oxygen in a given amount of time using a respirometer as shown below:

1. Set up the respirometer as shown above. One tube should contain the insect being investigated e.g. a woodlice, and the other tube should contain beads of the same mass to act as a control.
2. Both tubes should have Sodium Hydroxide. This absorbs and removes the carbon dioxide produce so any volume changes in the tubes is only due to the oxygen.
3. Set up the water bath at 10°C and set the liquid in the manometer to a known level using the syringes.
4. After the set up is complete, start your stopwatch. Time how long it takes for the liquid in the manometer to move a certain distance towards the woodlice.
5. Calculate the rate of respiration. The distance moved can help you work out the volume of oxygen taken up by the woodlice per minute thus, giving you the rate of respiration in cm3/min.
6. Repeat steps 3-5 but with the water bath at different temperatures e.g. 15°C, 20°C, 25°C etc. You will see the rate of respiration changes with temperature.

Detecting Carbon Dioxide Production

You can see the evolution of carbon dioxide from respiring beans using a hydrogen-carbonate indicator:

1. Set up a tube with some hydrogen-carbonate, placing a gauze on top with some germinating beans on there and seal the tube with a rubber bung. You can get dried beans to germinate by soaking them in water.
2. Set up another tube in the same way but with dead beans of the same amount (you can boil the beans to kill them). This is your control tube.
3. Observe the colour changes over time. In the tube with the germinating beans, you will see the hydrogen carbonate change from orange to yellow due to the production of carbon dioxide. The other tube will remain orange.

Detecting Heat Generation

You can see the generation of heat from respiring beans :

1. Prepare a set of germinating beans and dead beans.
2. Place them in separate vacuum flasks each with a thermometer.
3. Cover the top with some cotton wool, leaving some air in to allow the beans to respire aerobically.
4. Leave the beans aside and measure the temperature everyday for a few days. You will notice the germinating beans flask will have an increasing temperature as the beans are respiring whereas the other flask won’t.