Buffer System of Blood and Exchange of Oxygen and Carbon Dioxide

carbonic anhydrase type II (CA II). THis is an isoenzyme that is caused by an autosomal disorder.

Deficiency of what enzyme leads to osteopetrosis (marbel bone disease), renal tubular acidosis, and cerebral calcification?

Deoxyhemoglobin.

Does CO2 combine most closely to deoxyhemoglobin or oxyhemoglobin?

H+ ions are removed by the buffering action of hemoglobin

How does H2CO3 (carbonic acid), a weak acid, dissociate 100% into H+ and HCO3-?

1) Transportation of H+ ions and other anions in buffer systems. 2) Elimination of CO2 through alveolar ventilation in the lungs 3) Excretion of aqueous acids in the urine.

How is a constant pH maintained when the body metabolism produces large amount of acid?

1) The pressure of O2 in the blood is greater than the pressure of O2 in the tissue cells. 2) Protonated deoxyhemoglobin (HHb) is a weaker acid than oxyhemoglobin (HbO2) and thereby binds to H+ more strongly than HbO2.

What are the two reasons why oxygen diffuses into the tissues?

Dehydration of H2CO3 and release of CO2 from the red blood cells occurs.

What does Carbonic anhydrase do in the schematic above?

catalyzes the hydration reaction of CO2 in osteoclasts and renal tubule cells.

What does carbonic anhydrase type II (CAII) do?

carbonic anyhydrase of the red blood cells. This is a monomeric zinc metalloenzyme (MW 29,000) that has Zn++ held by three histidine residues. This plays a role in CO2 transport and elimination.

What enzyme converts CO2 to HCO3- (bicarbonate ion)?

Carbamino Hb or hemoglobin carbamate forms in order to lower the affinity of hemoglobin for oxygen. Hence, increased CO2 favors dissociation of oxyhemoglobin (HbO2) to oxygen and deoxyhemoglobin (HHb)

What forms when a small percentage of CO2 entering the red blood cell combines reversibly with an unionized among group (--NH2) of hemoglobin?

HCO3- efflux to plasma and Cl- and H2O influx to red blood cells to balance the the electrostatic charges. This is called chloride shift.

What happens when HCO3- in the red blood cells increase? What is this occurrence called?

The corresponding efflux of Cl- combines with released H+ to form H2CO3

What happens when bicarbonate is released and transported to the red blood cells?

A very soluble anion known as HCO3- (bicarbonate). This is the most efficient way to transport insoluble C02 from the tissues where it is formed to the lungs where it must be exhaled.

What is CO2 most transported as in the plasma? and Why?

The effect of pH on the binding of O2 to hemoglobin.

What is the Bohr effect?

1) Formation of H+ ion in stomach parietal 2) Bone resoprtion by the oteocalsts 3) reclamation of HCO3- in renal tubule cells

What is the importance of carbonic anhydrase (CA) in metabolic functions?

-This represents the transfer of CO2 from the alveolus (and its loss in the expired air in the lungs) and oxygenation of hemoglobin.

What is the importance of this schematic figure?

Imidazolium group of histidine residue in hemoglobin (pK' of 6.5).

What is the major buffering group involved in the transport of H+?

CO2.

What is the major metabolic product from oxidation of ingested carbon compounds?

carbonic anhydrase type I (CAI).

What is the most prevalent red blood cell isoenzyme of carbonic anhydrase?

50 mmHg

What is the pressure of CO2 in the peripheral tissues?

40 mmHg

What is the pressure of CO2 when blood enters the tissue capillaries?

Hemoglobin

What is the principal buffer in the red blood cell?

95%

What percent of CO2 enters the blood diffused into the red blood cells where enzyme carbonic anhydrase catalayzes converts it to H2CO3?

6.8 or 7.8 could mean death

What plasma pH levels are dangerous to the human body?

CO2 + H2O

What two products form the weak acid H2CO3 (carbonic acid)?

This represent the transport of CO2 from the tissues to the blood.

What's the importance of this schematic figure?

When CO2 diffuses through the cell membranes of capillary endothelium

When does blood pressure CO2 rise to 45-45 mmHg?

HbO2 is a stronger acid than deoxyhemoglobin (HHb).

Why does H+ release take place?

Alveolar pressure of O2 is higher than that of the incoming deoxygenated blood.

Why does oxygenation of hemoglobin occur and the release of H+ occur?