Respiration

- cellular respiration is an exothermic reaction that occurs continuously in living cells

    aerobic respiration is summarised as:

    glucose + oxygen ---> carbon dioxide + water (energy transferred to the environment)

    the energy transferred supplies all the energy needed for living processes

- the energy that is transferred during respiration is used to enable muscles to contract

- during exercise the human body responds to the increased demand for energy 

- body responses to exercise include:

    an increase in the heart rate, in the breathing rate and in the breath volume

    glycogen stores in the muscles are converted to glucose for cellular respiration

    the flow of oxygenated blood to the muscles increases

- these responses act to increase the rate of supply of glucose and oxygen to the muscles and the rate of supply of glucose and oxygen to the muscles and the rate of removal of carbon dioxide from the muscles

- if muscles work hard for a long time, they become fatigued and don't contract efficiently, if they don't get enough oxygen, they will respire anaerobically

- anaerobic respiration is respiration without oxygen, when this takes place in animal cells, glucose is incompletely broken down to form lactic acid

- the anaerobic breakdown of glucose transfers less energy than aerobic respiration 

- after exercise, oxygen is stll needed to break down the lactic acid that has built up, the amount of oxygen needed is known as the oxygen debt

- anaerobic respiration in plant cells and some microorganisms, such as yeast, results in the production of ethanol and carbon dioxide

- metabolism is the sum of all the reactions in the body

- the energ tranferred by respiration in cells is used by the organism for the continual enyme- controlled processes of metabolism that synthesise new molecules

- metabolism includes the conversion of glucose to starch, glycogen and cellulose, it also includes the formation of lipid molecules, and the use of glucose and nitrate ions to form amino acids, which are used to synthesise proteins and breakdown excess proteins to form urea

- blood flowing through the muscles transports lactic acid to the liver where it is converted back to glucose