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ICSE Question Bank
2019Q1(a)(v)The Circulatory System
Biological termHard1 mark
1(a)

Name the following:

The compound formed when haemoglobin combines with carbon dioxide in blood.

Topic: Carbaminohaemoglobin

Previous-year question practice database

Answer

Exam answer

CARBAMINOHAEMOGLOBIN.

Explanation

Learn the three compounds of haemoglobin together, because papers ask for any of them: OXYHAEMOGLOBIN — haemoglobin + OXYGEN. Unstable, so it releases oxygen readily at the tissues. CARBAMINOHAEMOGLOBIN — haemoglobin + CARBON DIOXIDE. Also unstable, releasing CO₂ at the lungs. CARBOXYHAEMOGLOBIN — haemoglobin + CARBON MONOXIDE. Very STABLE, which is exactly why carbon monoxide is lethal: the haemoglobin is permanently occupied and can no longer carry oxygen.

THE SPELLING TRAP: CARBAMINO- (carbon dioxide) and CARBOXY- (carbon monoxide) differ by a few letters and mean the difference between normal respiration and poisoning.

Note that most carbon dioxide is actually carried as bicarbonate in the plasma; only about 20-25% travels bound to haemoglobin.

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