Aerobic respiration
Aerobic respiration is defined as chemical reactions in cells that use oxygen to break down nutrient molecules to release energy.
The energy released from respiration are used for various things in the body:
- Muscle contraction
- Protein synthesis
- Cell division
- Active transport
- Growth
- Passage of nerve impulses
- Maintenance of constant body temperature
Investigation: Oxygen uptake by respiring organisms
A simple respirometer is used. An organism is placed in the boiling tube on top of the wire gauze. A capillary tube connected to the boiling tube is measured against a ruler, and a colored dye is introduced into it.
With the starting point of the dye measured, the dye will move towards the boiling tube as the organism uses up the oxygen in the air.
The carbon dioxide produced by the organism is eliminated/absorbed by the soda lime, and therefore does will affect the dye position.
We can measure the rate of respiration by calculating the distance traveled by the dye and dividing it by the time it took.
Investigation: The effect on temperature on rate of respiration of germinating seeds
The experimental set up for this experiment is virtually the same before.
Germinating seeds are placed in a boiling tube on a wire gauze. Soda lime is placed at the bottom (to absorb CO2) and the boiling tube is placed in a water bath of a known temperature (i.e. 30 degrees)
A capillary tube is connected to the boiling tube, with colored dye introduced. The initial position of the dye is measured against a ruler and as the seeds respire, the dye will move towards the boiling tube.
The rate of respiration for that particular temperature (i.e. 30 degrees) is calculated:
The experiment can be repeated multiple times to calculate and compare the rate of respiration at different temperatures i.e. 40°C , 50°C, etc.
Anaerobic respiration
Anaerobic respiration is defined as chemical reactions in cells that break down nutrient molecules to release energy without oxygen.
Anaerobic respiration releases less energy per glucose than aerobic respiration, so it is less efficient.
The equation for anaerobic respiration is different between our muscles and yeast:
- In muscles:
- In yeast
Lactic acid
Oxygen debt
During vigorous exercise muscles may not be receiving oxygen quick enough for aerobic respiration. In such instances, anaerobic respiration occurs in order to supply the muscles with energy despite the lack of oxygen.
As we see in the equation above, anaerobic respiration in muscles produces lactic acid, which is a toxic waste product.
Oxygen is required to remove lactic acid once the exercise stops, and therefore we call this ‘oxygen debt’ i.e. the body ‘borrowed’ oxygen during anaerobic respiration, and must pay it back to remove the lactic acid.
Lactic acid removal
Lactic acid is aerobically respired in the liver.
Even after exercise stops, the heart rate remains quick and the breathing rate remains deep.
- Fast heart rate allows lactic acid to be transported quickly from the muscles to the liver
- Deep breathing rate allows sufficient supply of oxygen to aerobically respire/remove the lactic acid