Blood

1. Blood Compositions and Their Functions.

2. Important Functions Of Blood

• Supply of oxygen to tissues (bound to hemoglobin, which is carried in red cells).
• Supply of nutrients such as glucose, amino acids, and fatty acids (dissolved in the blood or bound to plasma proteins (e.g., blood lipids)).
• Removal of waste such as carbon dioxide, urea, and lactic acid.
• Immunological functions, including circulation of white blood cells, and detection of foreign material by antibodies.
• Coagulation, the response to a broken blood vessel, the conversion of blood from a liquid to a semisolid gel to stop bleeding.
• Messenger functions, including the transport of hormones and the signaling of tissue damage.
• Regulation of core body temperature.
• Hydraulic functions.

3. Hematopoiesis

4. Structure and Functions Of RBCs

#RBCs
Adult humans have roughly 20–30 trillion red blood cells at any given time, constituting approximately 70% of all cells by number. Women have about 4–5 million red blood cells per microliter (cubic millimeter) of blood and men about 5–6 million; people living at high altitudes with low oxygen tension will have more.

#Functions of RBCs

The primary function of red blood cells is to carry oxygen from the lungs to the body tissues and carbon dioxide as a waste product, away from the tissues and back to the lungs. Hemoglobin (Hb) is the protein in the red blood cells that carries oxygen from the lungs to all parts of our body.

#Structure of RBCs
A typical human red blood cell has a disk diameter of approximately 6.2–8.2 µm and a thickness at the thickest point of 2–2.5 µm and a minimum thickness in the centre of 0.8–1 µm, being much smaller than most other human cells. These cells have an average volume of about 90 fL with a surface of about 136 μm², and can swell up to a sphere shape containing 150 fL, without membrane distension.

5. Synthesis and Structure Of Hemoglobin

Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells. Hemoglobin in the blood carries oxygen from the lungs to the rest of the body (i.e. the tissues). There it releases the oxygen to permit aerobic respiration to provide energy to power the functions of the organism in the process called metabolism. A healthy individual has “12 – 16” grams of haemoglobin in every 100 ml of blood.

#Synthesis Of Hb

Hemoglobin (Hb) is synthesized in a complex series of steps. The heme part is synthesized in a series of steps in the mitochondria and the cytosol of immature red blood cells, while the globin protein parts are synthesized by ribosomes in the cytosol. Production of Hb continues in the cell throughout its early development from the proerythroblast to the reticulocyte in the bone marrow. Even after the loss of the nucleus of RBCs, residual ribosomal RNA allows further synthesis of Hb until the reticulocyte loses its RNA soon after entering the vasculature.

#Structure Of Hb

Hemoglobin molecule consists of 2 parts viz. Hem and Globin. A Hb molecule has 4 hem-molecule attaching with each molecule with a polypeptide chain. Therefore, Hb molecule has 4 iron (Ferrous) atom and thus each Hb molecule can combine with 4 molecules (8 atom) of oxygen. The molecular weight of Hb is 64,000 Dalton.

Hem – It is an iron contaning compound and belongs to the class protoporphyrins. In a hem molecule, there are 4 pyrole structure linked with one another by methine (=CH) bridge containing iron in the central part. The molecule formed is called iron protoporphyrin.

Globin – It is belongs to the class of protein called globulins. The globin molecule contains 4 polypeptide chains. Two of them contains chain of 141 amino acids named as alpha chains and other two called beta chains have 146 amino acids.