Bicarbonate buffer system

H₂CO₃ ⇌ H⁺  + H₂CO₃ ^– —- i)

Or, K1 = [H⁺] [ HCO₃] / [H₂CO₃] — ii)

Also,

CO₂ (d) + H₂O ⇌ H₂CO₃ —-iii)

K2 = [H₂CO₃] / [CO₂ (d)] + [H₂O]—iv)

Again,

CO₂(d) ⇌ [CO₂ (g)]

or, K3 = [CO₂] / [CO₂ (g)] —– v)

Overall process,

H⁺ + HCO₃ – ( in body) —–à H₂CO₃ – H₂O–à CO₂(d) -à CO_2­(g) ( Lung air space)

a. During exercise, H⁺ from lactic acid produced in muscle tissue is added to blood.

• Concentration of H₂CO₃ increase in tissue
• This increase CO₂(d) level in blood plasma
• CO₂(g) increase in air space of lungs
• Extra CO₂ is exhaled.

b. pH of blood increase by production of NH₃ during protein degradation,

• H⁺ in blood plasma is lowered.
• Leads to H₂CO₃ to dissociate into H⁺ and HCO₃ –
• More CO₂(g) from lungs dissolve in blood plasma.