#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 O₂ is 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 t^o is important because fermentation is controlled by enzymes

- when dough is cooked, high t^o 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