Question 1

How does haemoglobin transport oxygen?

Accepted Answer

Haemoglobin contains four globin subunits, and each subunit has one haem group with an Fe²⁺ ion capable of binding one oxygen molecule. Therefore, one haemoglobin molecule can bind a maximum of four O₂ molecules, while most oxygen in blood is transported in this bound form.

Question 2

How are oxygen and carbon dioxide exchanged in a systemic tissue capillary?

Accepted Answer

Blood flows from the arterial end toward the venous end. Oxygen diffuses from blood into tissue cells, while carbon dioxide diffuses from tissue cells into the blood.

Question 3

What does carbonic anhydrase do inside an RBC?

Accepted Answer

Carbonic anhydrase is an intracellular red blood cell enzyme that catalyses the conversion of carbon dioxide and water into carbonic acid, which dissociates into H⁺ and HCO₃⁻. This is a central step in carbon dioxide transport.

Question 4

What is the chloride shift?

Accepted Answer

In systemic tissue capillaries, bicarbonate ions leave the red blood cell and enter the plasma while chloride ions move into the red blood cell. This exchange helps maintain electroneutrality and is reversed in the lungs, where bicarbonate returns to the RBC and chloride leaves it.

Question 5

How is carbon dioxide transported in blood?

Accepted Answer

The major form is bicarbonate in plasma, accounting for about 70% of transported CO₂. Approximately 20–25% is carried by RBCs as carbamino-haemoglobin, and about 7% remains dissolved in plasma.

Oxygen & CO2 Transport 3D — Haemoglobin, Carbonic Anhydrase & Chloride Shift

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