Carbonic Acid-Bicarbonate Buffer

Question 1

Most carbon dioxide is converted to

Answer 1

Carbonic acid; which then dissociates into a hydrogen ion and a bicarbonate ion

Question 2

The carbonic acid bicarbonate buffer system is formed by

Answer 2

The carbonic acid and it’s dissociation products

Question 3

The primary role of this buffer system

Answer 3

Is to prevent changes in pH caused by organic acids and fixed acids in the ECF

Question 4

The carbonic acid bicarbonate buffer system reaction

Answer 4

Carbon dioxide + water ↔️ carbonic acid ↔️ hydrogen ion + bicarbonate ion
CO2 + H2O ↔️ H2CO3 ↔️ H + HCO3

Question 5

This reaction takes the hydrogen ion released by a strong organic or fixed acid and generates

Answer 5

A volatile acid that can easily be eliminated

Question 6

The carbonic acid bicarbonate buffer system can also protect against

Answer 6

Increases in pH

Question 7

Three important limitations of the carbonic acid bicarbonate buffer system

Answer 7

1. It cannot protect the ECF from changes in pH that result from increased or decreased levels of CO2.
2. It can function only when the respiratory system and the respiratory control centers are working normally.
3. The ability to buffer acids is limited by the availability of bicarbonate ions. Every time a hydrogen ion is removed from the plasma, a bicarbonate ion goes with it. When all the bicarbonate ions have been tied up, buffering capabilities are lost.

Question 8

Bicarbonate reserve

Answer 8

Body fluid contain a large reserve of bicarbonate mostly in the form of dissolved molecules of the weak base sodium bicarbonate (NaHCO3)
Na + HCO3 ↔️ NaHCO3

Question 9

When hydrogen ions enter the ECF, the bicarbonate ions tied up in H2 CO3 molecules are replaced by

Answer 9

Bicarbonate ions HC03, from the bicarbonate reserve

Question 10

How can additional bicarbonate ions be generated by the kidneys

Answer 10

1. In the distal convoluted tubule and collecting system, bicarbonate anhydrase converts CO2 within tubular cells into H2 CO3, which then dissociates.
2. The hydrogen ion is pumped into tubular fluid in exchange for a sodium ion, and the bicarbonate ion is transported into Peritubular fluid in exchange for a chloride ion.
3. In effect, tubular cells remove HCl from peritubular fluid in exchange for NAHCO3