4.2.1 Aerobic and anaerobic respiration
Cellular respiration
- An exothermic reaction which is continuously occurring in living cells
Organisms need energy for
- Chemical reactions to build larger molecules
- Movement
- Keeping warm
As oxidation of glucose is incomplete in anaerobic respiration, much less energy is transferred than in aerobic respiration
Fermentation
- Anaerobic respiration in yeast cells
- Has economic importance in the manufacture of bread & alcoholic drinks
4.2.2 Response 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
- Incomplete oxidation of glucose causes build-up of lactic acid & 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 – amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells
Explain how change in stroke volume / heart rate / breathing rate / breathing depth during exercise helps an athlete.
- Increases stroke volume means that with each heart beat the heart pumps more blood around the body
- Increases supply of O2 & glucose to muscle cells for more respiration to release more energy for muscle contraction
4.2.3 Metabolism
Metabolism – sum of all the reactions in cell / body
Energy transferred by respiration in cells is used by organism for continual enzyme-controlled processes of metabolism that synthesise new molecules.
Metabolism includes
- Conversion of glucose to starch, glycogen & cellulose
- Formation of lipid molecules from a molecule of glycerol & 3 molecules of fatty acids
- Use of glucose & nitrate ions to form amino acids which in turn are used to synthesise proteins
- Respiration
- Breakdown of excess proteins to form urea for excretion