Biological Chemistry - Berezov T. T., Korovkin B. F. 1998

Blood
Chemical Composition of Blood
Blood Cells

In humans, 1 μl of Blood contains 5 ∙ 10⁶ erythrocytes (red blood Cells), which are produced in the Bone Marrow. Mature erythrocytes in humans and other mammals lack a Nucleus and are almost entirely filled with Hemoglobin. The average lifespan of these cells is 125 days. Erythrocytes are broken down in the Spleen and Liver. The concentration of hemoglobin in the blood depends on the total number of erythrocytes and the hemoglobin content within each of them. Therefore, hypochromic, normochromic, and hyperchromic anemias are distinguished depending on whether the drop in blood hemoglobin levels is associated with a decrease or increase in its content per single erythrocyte.

The majority of an adult's hemoglobin is HbA₁ (96–98% of the total hemoglobin content), with small amounts of HbA₂ (2–3%) and HbF (less than 1%), the latter being abundant in the blood of newborns. Genetically determined abnormal Hemoglobins are found in the blood of certain individuals (see Chapter 2), with over 100 such hemoglobin types described in total. The appearance of abnormal hemoglobin types in the blood frequently leads to characteristic anemias known as "hemoglobinopathies" or "hemoglobinoses." It should be noted that Glycolysis and the Pentose Phosphate Pathway proceed intensively within erythrocytes.

The leukocyte count in 1 μl of blood is approximately 7 ∙ 10³, which is nearly 1,000 times lower than that of erythrocytes. Unlike erythrocytes, leukocytes are fully functional cells with a large nucleus, Cell/35.html">Mitochondria, and a high nucleic acid content. They concentrate all the Glycogen found in blood, which serves as an energy source during oxygen deprivation, such as in areas of inflammation.

Leukocytes comprise 3 types of cells: lymphocytes (26% of the total leukocyte count), monocytes (7%), and polymorphonuclear leukocytes, or granulocytes (70%). Staining with various Dyes reveals 3 types of granulocytes: neutrophils, eosinophils, and basophils.

Lymphocytes are produced in lymphoid tissue, and their primary function is The production of Antibodies, specifically IMMUNOGLOBULINS. Monocytes are twice the size of lymphocytes and are capable of phagocytizing bacterial cells. Granulocytes are formed in the Cytology/practical/86.html">Red bone marrow and perform various Functions; for example, The primary function of neutrophils is phagocytosis.

Finally, the blood contains Blood Platelets, or thrombocytes, which are formed from the Cytoplasm of bone marrow megakaryocytes. Platelets cannot be considered fully functional cells since they lack a nucleus; however, all major biochemical processes take place within them: Protein Synthesis, carbohydrate and Lipid METABOLISM, biological Oxidation coupled with phosphorylation, etc. The primary physiological function of blood platelets is Participation in the blood clotting process.