Bulk of carbon dioxide (CO2 ) released from body tissues into the blood is present as (a)

Explanation

All options are explained below: a)Bicarbonate in blood plasma and RBCs (Correct Option):The bulk of carbon dioxide (CO2) released from body tissues into the blood is present as bicarbonate ions (HCO3-) in both blood plasma and red blood cells (RBCs). This process involves the conversion of CO2 to carbonic acid (H2CO3) and its subsequent dissociation into bicarbonate ions (HCO3-) and hydrogen ions (H+). This bicarbonate system plays a major role in transporting CO2 from body tissues to the lungs for elimination. B. Free CO2 in blood plasma: While some CO2 is transported as free CO2 molecules in blood plasma, it is a relatively smaller proportion compared to the bicarbonate form. The majority of CO2 is carried as bicarbonate ions and carbamino compounds. C. 70% carbamino-hemoglobin and 30% as bicarbonate:This option presents an inaccurate distribution of CO2 forms. Carbamino-hemoglobin refers to CO2 bound to hemoglobin within red blood cells, which is a smaller fraction compared to bicarbonate transport. The majority of CO2 is transported as bicarbonate ions, while some is bound to hemoglobin. D. Carbamino-hemoglobin in RBCs:While CO2 can bind to hemoglobin within red blood cells (carbamino-hemoglobin), it is not the primary form of CO2 transport. The primary method is the conversion of CO2 to bicarbonate ions, as explained in option A. Correct Option: A. Bicarbonate in blood plasma and RBCs. Summary: The correct option is A. The bulk of carbon dioxide (CO2) released from body tissues into the blood is primarily present as bicarbonate ions (HCO3-) in both blood plasma and red blood cells (RBCs). This bicarbonate system is the major method of CO2 transport from the tissues to the lungs for elimination. The other options either describe smaller fractions of CO2 transport or present inaccuracies in the distribution of CO2 forms.