Protein Chemistry: Structure, Properties, and Research Methods - Shendryk, A.N. 2022

Proteins of blood and muscle tissues
Circulatory system
Blood oxygen transport

At rest, human Tissues consume about 200 ml of oxygen per minute. During physical and mental exertion, O2 consumption increases tenfold or more (2-3 l/min.). Delivering this amount of oxygen to the tissues simply through physical dissolution in plasma is impossible. The solubility of O2 in plasma is extremely low (0.023 ml/ml at 40∘С, PO2 = 1 atm.) and can only cover 0.3% of the body's oxygen demand. Therefore, virtually all oxygen is delivered to the tissues in a form bound to Hemoglobin.

Hemoglobin (Hb) is an oligomeric protein consisting of 4 peptide chains, each containing a single heme group. The iron content in hemoglobin is 0.335%. One gram-atom of Fe (55.84 g) in Hb binds 1 mole of O2 (22.4 l). Consequently, 100 g of hemoglobin is capable of binding: (0.335∙22400 ml)/55.84 = 134 ml of O2.

The hemoglobin content in Blood is (13-16 g)/100 ml of blood. Taking into account the turnover rate of hemoglobin in the bloodstream, this amount is entirely sufficient to fully supply tissues with oxygen.

In addition to transporting oxygen to Cells, hemoglobin performs another crucial function — it carries carbon dioxide to the Lungs. The Mechanism of this transport is as follows: the deoxygenated form of hemoglobin (HHb) binds СО2 in the form of carbonic acid to form carbaminohemoglobin:

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Carbaminohemoglobin is an unstable compound that dissociates in the pulmonary capillaries, releasing СО2. Between 3 and 10% of СО2 is transported from the tissues to the lungs in the form of carbaminohemoglobin.



Last update: 06/08/2026

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