MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 4. BLOOD SYSTEM

GAS TRANSPORT BY BLOOD

3. HEMOGLOBIN

Erythrocytes contain a red pigment called Hemoglobin. A hemoglobin molecule consists of 1 globin protein molecule and 4 heme molecules, each containing an iron atom capable of reversibly binding and releasing oxygen. The valence of iron remains constant (divalent) during this process.

Hemoglobin binds with gases to form the following compounds:

Oxyhemoglobin (НвС>2) is an unstable compound of hemoglobin and oxygen. In the pulmonary capillaries, where the partial pressure of oxygen is higher than in the Blood, hemoglobin becomes saturated with oxygen, thereby transporting it throughout the body.

Deoxyhemoglobin, or reduced hemoglobin, is hemoglobin that has released its oxygen to the Tissues.

Carbaminohemoglobin (НвСС>2) is a transport form of globin and carbon dioxide. Through this compound, globin transports carbon dioxide from the tissues to the Lungs.

Methemoglobin (МШв) is a compound of hemoglobin and oxygen in which iron is oxidized to a trivalent state by the action of strong oxidizing agents.

Carboxyhemoglobin (НвСО) is a compound of hemoglobin with carbon monoxide. Unlike oxyhemoglobin, it is quite stable; it releases carbon monoxide slowly, over a long period, and only upon breathing pure air.

The affinity of hemoglobin for CO is hundreds of times greater than its affinity for С>2. For this reason, the oxygen-carrying capacity drops sharply, and Carbon monoxide poisoning is life-threatening. Normally, the blood of a healthy male contains 130-160 g/L of hemoglobin, while that of a female contains 120-140 g/L.