Energy from respiration

glucose + oxygen --> carbon dioxide + water [ + energy ]

the enrgy released may be used in organisms to:

• biuld larger molecules from smaller ones
• enable muscle contraction in animals
• maintain a constant body temperature
• build sugars, nitrates and other solutions

limewater- test for carbon dioxide

rise in temperature- test for respiration 

Glucose --> lactic acid + energy

lactic acid is a toxic waste product

if lactic acid builds up too much, it stops the muscles contracting and relaxing and they become fatigued

after aerobic respiration the body must get rid of lactic acid

lactid acid + oxygen --> carbon dioxide + water

when exercise has finished the lactic acid must be completely broken down. You still need to take in a lot of oxygen to do this. The extra oxgen needed is the 'oxygen debt'