Excretion

Excretion is the removal of metabolic waste from the body. 

CO2 from respiration must be removed. 

It is usually transported in the blood as hydrogencarbonate ions to the lungs where it diffuses into the alveoli. 

CO2 causes hyrdrogencarbonate ions which from hydrogen ions. Under the influence of the enzyme carbonic anhydrase H+ ions combine with haemoglobin which competes with oxygen for space on the haemoglobin reducing oxygen transport. 

CO2 combines with haemoglobin to form carbaminohaemoglobin which has a lower affinity for oxygen. 

Excess CO2 can cause respiratory acidosis. CO2 dissolves in the blood plasma and forms carbonic acid when combined with water, which in turn produces…