Red blood cells are the most common type of blood cell.
They are the primary means of delivering oxygen to your body tissues. Red cells take up oxygen from the lungs and carry it to tissues. They are also known as erythrocytes. Apart from erythrocytes, other major blood components are white blood cells, platelets, and plasma.
The red cell cytoplasm is rich in hemoglobin. Hemoglobin is an iron-containing molecule that binds oxygen. It gives the red color of the blood. Its cell membrane contains lipid and protein.
Mature red blood cells have oval biconcave disks shape which makes it flexible. This structure enhances the properties needed for physiological cell function like deformability and stability. It also helps in achieving the different functions of erythrocytes.
Red Blood Cells Lack Nucleus and DNA
Red Cells don’t have a nucleus and most organelles. It also lacks lysosomes, endoplasmic reticulum, and mitochondria. The red blood cell loses its nucleus as it matures. The nucleus contains the DNA. This DNA contains the instructions for growth, development, reproduction and other genetic functions.
Because of this loss of nucleus, a mature red blood cell lacks the ability to replicate. No Nucleus implies no DNA. Without the DNA, the cell will not be able to replicate themselves.
Importance of No DNA in Red Blood Cell
There are many benefits for the red cell as it lacks Nucleus and DNA.
1. It creates more space for hemoglobin.
This results in transportation of more oxygen. Hemoglobin efficiently helps in carrying oxygen to the tissues from the lungs. It also transports carbon dioxide and hydrogen ions back to the lungs.
Hemoglobin bind to gaseous nitric oxide (NO) as well. When red blood cells pass through the capillary beds of the lungs, oxygen diffused into the erythrocytes. Then, the hemoglobin binds to the oxygen and nitric oxide.
This hemoglobin now offloads into the capillaries. Here, oxygen is diffused into the body cells. Nitric oxide helps in relaxing the walls of the capillaries. This allows them to expand and thus helps in the delivery of oxygen to the cells.
Hemoglobin has four subunits with each containing a heme group. This heme has an iron atom center. Iron is the main component of hemoglobin that binds to oxygen. Hence, each hemoglobin molecule will carry four molecules of oxygen.
Like other proteins, hemoglobin is coded for by DNA. There can be alterations or mutations in hemoglobin. This will result in blood-related diseases like sickle-cell anemia. The sickle cell structure is easily distorted. This cause reduces the oxygen-carrying capacity of the blood.
2. It also enables the red cell to have its bi-concave shape.
This aids diffusion and gas exchange. This shape would be affected and it might not be possible if there is a nucleus in the cell. The characteristic biconcave disc shape also provides a surface area to volume ratio that is optimal for gas exchange.
Gas exchange is the main function of red cells. This is the process by which human exchange gases between the cells and the environment. This is also called respiration. These gases (oxygen and carbon dioxide) are transported through the cardiovascular system of the body.
When the heart circulates blood, the oxygen-depleted blood is returned to the heart and then pumped back to the lungs. Oxygen is obtained from the respiratory system activity. In hereditary spherocytosis, red cells become spherical and losses it’s the bi-concave shape.
Fact: When blood DNA tests are done, other blood cells and components are used to check for DNA, not red cells. This is because there is no DNA in red blood cells.
How Are Red Blood Cell Formed?
They are derived from stem cells in bone marrow. They are formed through the process called erythropoiesis. Erythropoiesis is stimulated when the levels of oxygen in the blood are low. The oxygen levels are reduced when there is blood loss. It is also reduced in conditions like exercise, bone marrow damage, in high altitude, and low hemoglobin levels.
The kidneys detect the low oxygen levels and release a hormone called erythropoietin. Erythropoietin stimulates the formation of red blood cells. When there are more red blood cells in the blood circulation, oxygen levels increase in the blood and tissues.
As there is an increase in oxygen levels in the blood, the kidneys sense this and slow down erythropoietin release. Thus, red blood cell production will be decreased.
Due to the lack of a nucleus and other organelles in mature red blood cells, they can not undergo mitosis to generate new cell structures. As they get old or damaged, spleen, liver, and lymph nodes help in removing them from circulation.
These organs have white blood cells called macrophages which engulf and digest dying blood cells. Red cell degradation and erythropoiesis occur at the same rate to ensure homeostasis in red blood cell circulation.
A normal and mature red blood cell lacks a nucleus and thus DNA. They could not undergo mitosis and divide. This enables it to accommodate enough hemoglobin as it also retains its flexible biconcave shape.
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