21 May 2013

#80 Aerobic and anaerobic respiration

Respiration releases energy from food.

There are 2 kinds of respiration: Aerobic and Anearobic. The main difference between them is that aerobic respiration involves oxygen and anaerobic respiration does not!














A. Aerobic respiration

The release of a relatively large amount of energy in cells by the breakdown of food substances in the presence of O2.


B. Anaerobic respiration

Anaerobic respiration: the release of  a relatively small amount of energy by the breakdown of food substances in the absence of O2.

Anaerobic respiration in muscles during exercise:


Anaerobic respiration in yeast:


Muscles respire anaerobically when exercising vigorously, because the blood cannot supply enough oxygen to maintain aerobic respiration. Howerver, the formation and build-up of lactic acid in muscles causes cramp (muscle fatigue).

The lactic acid that is made is transported to the liver, and later is broken down by combining it with O2. This extra Ois breathed in after the exercise has stopped, and it is known as the oxygen debt 


Bread making
- yeast is mixed with water to activate it then added to flour to make dough
- mixture -----> warm place ------> rise
- yeast releases CO2 ------> dough rises
* a warm to is important because fermentation is controlled by enzymes
- when dough is cooked, high to kills yeast and evaporates any formed ethanol
- air spaces are left where CO2 was trapped


Brewing
- yeast is added to a source of sugar (fruit juice or germinated barley grains) and kept in warm conditions

- fermentation (yeast respires the sugar) occurs ------> ethanol is formed making the drink alcoholic

- CO2 makes the drink fizzy + sharp flavour

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