Binding and transporting oxygen to body tissues
Explanation
Haemoglobin is an iron-containing metalloprotein found in the red blood cells (erythrocytes) of vertebrates. It serves as the primary respiratory pigment essential for gas transport in the circulatory system.
- Facilitating blood clotting at wound sites is incorrect: The facilitation of blood clotting (coagulation) is the primary function of platelets (thrombocytes) and clotting factors such as fibrinogen, not haemoglobin.
- Binding and transporting oxygen to body tissues is correct: The main physiological function of haemoglobin is to bind reversibly with oxygen in the lungs (forming oxyhaemoglobin) and transport it to various body tissues for cellular respiration. It also plays a role in transporting carbon dioxide from tissues back to the lungs.
- Providing immunity against infectious agents is incorrect: Immunity and defense against infectious agents are functions performed by white blood cells (leukocytes) and antibodies, rather than red blood cells or haemoglobin.
- Transporting digested nutrients to cells is incorrect: The transport of digested nutrients, hormones, and waste products is primarily the function of blood plasma.
Key Takeaway: Haemoglobin is the oxygen-carrying pigment in red blood cells, crucial for delivering oxygen to tissues and maintaining aerobic metabolism.