Which of the following statements best describes haemoglobin? It is

Step 1: Analyze the question The question asks which statement best describes haemoglobin. We need to recall what haemoglobin is and what it does.

Step 2: Explain the concept Haemoglobin is a protein found inside red blood cells (erythrocytes). It contains iron (in the haem group), which binds to oxygen in the lungs to form oxyhaemoglobin. The blood carries this oxygen to the body tissues, where it is released. Haemoglobin is what gives red blood cells their red colour.

Step 3: Evaluate each option

• A. Yellowish in colour: Wrong. Haemoglobin is red (bright red when oxygenated, dark red when deoxygenated). The yellowish fluid in blood is plasma.
• B. A red blood cell: Wrong. Haemoglobin is a pigment inside the red blood cell, not the cell itself.
• C. An oxygen carrying pigment: Correct. Haemoglobin is a respiratory pigment that transports oxygen around the body.
• D. Needed for blood clotting: Wrong. Clotting involves platelets, fibrinogen, prothrombin, thrombin and vitamin K, not haemoglobin.

Step 4: Answer The correct option is C. an oxygen carrying pigment.

Exam tip: Remember "Haemoglobin = Haem (iron) + Globin (protein)", and it carries O₂. Also keep these pairs straight:

• Red blood cells carry oxygen (using haemoglobin)
• White blood cells fight infection
• Platelets help clotting
• Plasma carries dissolved substances