Tag: transportation in living organisms

Platelets are cell fragments produced from megakaryocytes (special cells in the bone marrow). They are also called as thrombocytes. An injury or a trauma stimulates the platelets in the blood to release certain factors which activate the mechanism of coagulation or blood clotting. They also change their shape from round to spiny and stick to the broken vessel wall and each other and forms net-like structure during bleeding. Hence platelets forms net-like structure during bleeding.

The beta-chain of haemoglobin in humans and rhesus monkeys is highly conserved, showing approximately 40% similarity in amino acid sequence.

Statement A is incorrect because plasma is about 55% of blood. Statement E is incorrect because minerals (electrolytes) are essential components of blood plasma. Statements B, C, and D are standard physiological facts.

Hemoglobin (Hb or Hgb ) is an iron-containing protein present in erythrocytes or Red blood cells(RBC) of almost all vertebrates. Each hemoglobin is made up of 4 subunits, 2 alpha subunits and 2 beta subunits. Each subunit surrounds the central heme group that contains iron and binds to one oxygen molecule. Hence each hemoglobin molecule can bind to four oxygen molecules. It carries oxygen from lungs to tissues. It also helps in the transportation of carbon dioxide, hydrogen ions back to the lungs from the tissues. Hence haemoglobin in the RBCs helps in the transport of oxygen and carbon dioxide.

A single haemoglobin molecule contains four haem groups, each capable of binding one molecule of oxygen, allowing a total of four oxygen molecules to be carried per haemoglobin molecule.

Carbon monoxide binds to haemoglobin with much higher affinity than oxygen, forming carboxyhaemoglobin. This effectively reduces the amount of free haemoglobin available to transport oxygen.

It is a standard physiological constant that 1 gram of pure haemoglobin can bind approximately 1.34 mL of oxygen when fully saturated.

(b) To maintain electrostatic neutrality of plasma, many chloride ions diffuse from plasma into RBCs and bicarbonate ions pass out. The chloride content of RBCs increase when oxygenated blood become deoxygenated. This is termed as chloride shift or Hamburger phenomenon.

While plasma carries some dissolved oxygen, the vast majority of oxygen transport in the body is carried by the blood, specifically within the red blood cells via haemoglobin.