Respiration:
- Cellular respiration is an exothermic reaction which is continuously occurring in living cells.
- The energy transferred supplies all the energy needed for living processes, such as -
- Chemical reactions to build larger molecules
- Movement
- Keeping warm
Aerobic Respiration:
| glucose + oxygen → carbon dioxide + water |
|---|
| C6H12O6 + 6O2 → 6CO2 + 6H2O |
Anaerobic Respiration:
| In muscles: glucose → lactic acid |
|---|
| In plant and yeast cells: glucose → ethanol + carbon dioxide |
- Anaerobic respiration in yeast cells is called fermentation and has economic importance in the manufacture of bread and alcoholic drinks.
Responses to Exercise:
- During exercise, the human body reacts to the increased demand for energy.
- The heart rate, breathing rate and breath volume increase during exercise to supply the muscles with more oxygenated blood.
- If insufficient oxygen is supplied anaerobic respiration takes place in muscles.
- The incomplete oxidation of glucose causes a build-up of lactic acid and creates an oxygen debt.
- During long periods of vigorous activity, muscles become fatigued and stop contracting efficiently.
- Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose.
- Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.
- Metabolism - the sum of all the reactions in a cell or the body.
- The energy transferred by respiration in cells is used by the organism for the continual enzyme-controlled processes of metabolism that synthesise new molecules.
- Metabolism includes -
- Conversion of glucose to starch, glycogen and cellulose
- Formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids
- The use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins
- Respiration
- Breakdown of excess proteins to form urea for excretion.
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