Mammals and birds need energy to maintain a constant body temperature. Energy is also needed for the following life processes:
Aerobic respiration needs oxygen. It is the release of a relatively large amount of energy in cells by the breakdown of food substances in the presence of oxygen: glucose + oxygen → carbon dioxide + water YOU NEED TO KNOW THIS!
Unlike aerobic respiration, anaerobic respiration does not need oxygen. It is the release of a relatively small amount of energy in cells by the breakdown of food substances in the absence of oxygen.
Anaerobic respiration happens in muscles during hard exercise:
glucose → lactic acid (when you get a stitch, ouch!)
Glucose is not completely broken down, so much less energy is released than during aerobic respiration.
The lactic acid needs to be oxidised to carbon dioxide and water later.
This causes an oxygen debt - known as excess post-exercise oxygen consumption This is why we keep on breathing deeply for a few minutes after we have finished exercising.
Investigating production of carbon dioxide
INVESTIGTING PRODUCTION OF CARBON DIOXIDE
Limewater turns milky in the presence of carbon dioxide. It can be used to show that exhaled air contains more carbon dioxide than inhaled air.
Carbon dioxide dissolves in water to form a weakly acidic solution. Hydrogencarbonate indicator is used to show the presence of carbon dioxide in solution. It is red when carbod dioxide is present and yellow when there is no carbon dioxide.
Investigating production of heat
INVESTIGATING HEAT PRODUCTION
The release of heat can be shown by carrying out an experiment using germinating seeds. Two vacuum flasks are used:
one containing living plant material
one containing dead plant material - the control