Protein Defects Associated With Red Blood Cells Biology Essay

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Introduction

Red blood cells are the most common found cell in blood. Their main function is to carry oxygen around the body, from the heart to the extremities. All of the tissues of the body are dependent upon oxygen from red blood cells - if the flow is stopped the tissue dies. The scientific name by which red blood cell are known is "erythrocyte," meaning "hollow red cell." Red blood cells attains the red color from hemoglobin, which constitute around 97% of the dry weight of red blood cells, and about 35% of the total weight, including water. Bianco(2010)suggests that "Red blood cells (RBCs) are by far the most abundant cells in the blood. RBCs give blood its characteristic red color".

Hemoglobin is a metalloprotein, which means it is a protein that includes iron as one of its constituent atoms. For the reason of oxygen distribution, hemoglobin has multiple chemical "slots" for storing oxygen. This oxygen is acquired from the heart, where red blood cells are replenished with oxygen from the lungs. According toToole(2004: 32) "Red blood cells are unusual in having no nucleus, mitochondria and they are much thinner in the middle and so form a biconcave shape".

The red blood cell is the main component of the circulatory system, also known by the name of cardiovascular system. In the circulatory system, the channels know as arteries hold oxygen-rich blood for distribution to the body, while veins give back oxygen-poor blood to the heart for replenishment. The oxygen levels of blood can be assessed by looking at its color - oxygen-poor blood has bluish color, while oxygen-rich blood looks red. When exposed to the open through a wound, blood quickly gets combined with atmospheric oxygen, appearing as bright red. The second important function to carrying oxygen although less commonly known, is the capability of red blood cells to carry carbon dioxide. CO2 is a waste product formed due to metabolism in every cell in the human body. If this waste product is not taken of from the body we die quickly. Red blood cells serve as a means to get rid of this waste from the body.

Red blood cells measure a diameter of about 6-8 micrometers (millionths of a meter), similar in size to much of the cells in the body. An RBC is biconcave in shape.Rosenberge (2010)states that "Red blood cells completely lack in most other common cellular parts, such as a nucleus with DNA, or mitochondria". Due to their small shape and physical structure, the RBC can squish in to the small capillaries where the blood vessels are the smallest. Without this nature of flexibility , they have a high chance of getting stuck and cause obstructions in the circulation Because red blood cells are so important to your body, when they don't work properly, it often leads to disease(Annissimov)"Adult humans have 20 - 30 trillion red blood cells in their body, about 5 million per micro liter of blood. Other cells found in blood include platelets, which assist in clotting, and white blood cells, which serve as the blood's sentries against pathogens."

Diseases

Normal red blood cells are deformable concave disks. The external environment of the cell, the metabolic activity of the cell, the nature of hemoglobin, the membrane skeloton and the age of the cell determine the shape of the cell.Cavendish(2008:13)writes that "The red blood cells or erythrocytes last about 120 days, until they are eventually removed by the spleen". When RBCs are destroyed more quickly than normal by disease (a process called hemolysis), the bone marrow will produce for it by increasing production of new red cells to take their place. But if RBCs are deformed by any reason the person can suffer from various diseases. Four abnormalities in red cell membrane proteins have been identified and include (1) spectrin deficiency alone, (2) combined spectrin and ankyrin deficiency, (3) band 3 deficiency, and (4) protein 4.2 defects.(5)protein 4.1 deficiency.

Table 1: Table showing protein deficiency and genetic information

Protein Defect

Disease

Genetic Information

Spectrin deficiency

Hereditary elliptocytosis

Hereditary elliptocytosis (HE) is a congenital hemolytic disorder in which erythrocytes get elongated into a cigar or oval shape. Chromosome location - 1q22-q23.Mutations that obstruct the formation of spectrin tetramers result in hereditary elliptocytosis. Symptoms are hemolytic anemia, gall stones and fatigue.

Ankyrin deficiency

Hereditary Spherocytosis

Hereditary spherocytosis is a congenital haemolytic anemia due to defect in ankyrin-a RBC membrane protein. As a result of this defect there is presence of characteristic spherical cell in peripheral blood smear and osmotic fragility is increased.chromosome location-8p11·2..Symptoms are Severe anaemia, jaundice, splenomegaly and cholelithiasis

Band 3 deficiency

Sickle - cell disease

People with sickle cell disease possess red blood cells that consist mostly hemoglobin* S, an abnormal type of hemoglobin.Chromosme location - . 17q21-q22.Sickle cells are destroyed rapidly in the body of people with the disease causing anemia, jaundice and the formation of gallstones

Protein 4.1 deficiency

Hemolytic anemia

Hemolytic anemia is a disorder in which red blood cells are destroyed and removed from the bloodstream before their normal lifetime.It map to chromosme1p36·2-p34 . Hemolytic anemia can lead to various health problems, such as fatigue , pain, arrhythmias (ah-RITH-me-ahs), an enlarged heart, and heart failure.

Protein 4.2 deficiency

splenomegaly

In splenomegal the spleen is enlarged and it can result in cirrhosis andchronic infections. Hypersplenism is suspected in patients with splenomegaly and anemia or cytopenias.Chromosome locus is q15-q21

Glycphorin C deficiency

Ovalocytosis

Hereditary ovalocytosis is rare condition passed down through families (inherited) in which blood cells are slightly oval-shaped instead of round. Newborn infants with ovalocytosis may have anemia and jaundice. Adults usually do not show symptoms and are known as asymptomatic.

Glucose-6-phosphate dehydrogenase deficiency is a genetic disorder that happens mostly in males. This condition mainly occurs in red blood cells, which carry oxygen from the lungs to tissues throughout the body. Okpako refers that (1991:9)" People with this disease, has a defect in an enzyme called glucose-6-phosphate dehydrogenase causes red blood cells to break down prematurely". This destruction of red blood cells is known as hemolysis.G6PD is an enzyme that helps in protecting red blood cells from the destructive nature of certain chemicals found in foods and medications. When the enzyme becomes deficient, these chemicals can cause red cells to burst or hemolyze. G6PD deficiency is a widely seen hereditary disease among people of African, Southeast Asian and Mediterranean descent. According to Smith(2004:56-60)"G6PD is found among people who live ,or whose ancestors lived in regions of world where malaria is, or has been ,endemic".

Hereditary spherocytosis is an inherited condition in which RBCs lose their shape (like tiny spheres, ) and becomes fragile due to genetic problem with a protein in the structure of the red blood cell. This fragility makes the cells easily destroyed. Yawata(2003: 21)suggests that "The abnormalities of ankyrin are the principle cause in the pathogenesis for hereditary spherocytosis". Normal red blood cells have a shape like a disc. These round and fragile cells have difficulty to pass through certain organs unlike normal red blood cells. Because spherocytes does not change their shape easily, they remain in the spleen longer than normal red blood cells, and this makes the membrane surrounding the cell damaged.Castillo(2010:71-75)claims that "Symptoms of hereditary spherocytosis vary depending on the severity of the disease. Many people with hereditary spherocytosis have abnormal hemoglobin level"

Hereditary spherocytosis is most commonly seen in people of northern European ancestry. It often appears in infancy or early childhood, resulting in anemia and jaundice.According to Medicine net(1999) "The treatment of hereditary spherocytosis is to remove the spleen (splenectomy). Although the red cell defect persists, the breakup of the red cells (hemolysis) ceases. Splenectomy, however, is a hazard in young children"

Pyruvate kinase deficiency (PKD) is one of main seen enzymatic defects of the erythrocyte. This disorder is clinically known as a hemolytic anemia sometimes as a result of disease or for un known reason - the body's immune system mistakenly attacks and destroys RBCs. With inherited hemolytic anemias, more than one gene that control red blood cell production becomes faulty. The defects may have the hemoglobin, enzymes or cell membrane that maintains healthy red blood cells. The abnormal cells are fragile and tend to break down while moving through the bloodstream. When this happens, an organ called the spleen remove the cell debris from the bloodstream. A patient with mild hemolysis may be not show symptoms. In more serious cases, the anemia can be fatal, and patients can show angina and cardiopulmonary decompensation. The overall occurrence of death is low in cases of hemolytic anemia. Schick(2009)mentions that "However, older patients and patients with cardiovascular impairment are at an increased risk. Morbidity is dependent on the etiology of the hemolysis and the underlying disorder such as sickle cell anemia or malaria".

SCA is an autosomal recessive disease happened due to a point mutation in the hemoglobin beta gene (HBB) present in chromosome. A mutation in HBB leads to the production of a structurally defective hemoglobin. Hemoglobin is an oxygen carrying protein that gives red blood cells their red color. Under certain conditions, like low level of oxygen or high hemoglobin concentrations, in individuals who are homozygous for HbS, the abnormal HbS hold together, and give RBCs a sickled shape. This disease is most common in people of African descent, and it is a hereditary disease that causes the production of abnormal hemoglobin.Harris(2001)writes that "The people with sickle cell disease have inherited a mutated hemoglobin gene from each parent that carries faulty instructions fro making half of the hemoglobin molecule". The RBCs become sickle shaped, they become unable to carry oxygen adequately, and they are easily destroyed. The sickle-shaped blood cells usually tend to abnormally stick together, causing hindrance in the blood vessels. This blockage in the blood vessels can be very harmful and damage organs and cause bouts of severe pain.

Thalassemia is a blood disorder which passes down through families, in which the body makes a defective hemoglobin, the protein in red blood cells that carries oxygen. Schwartz( 1972:412-18)suggests that"The disorder results in excessive destruction of red blood cells, which leads to anemia. Hemoglobin is made of two proteins: Alpha globin and beta globin. Thalassemia occurs when there is a defect in a gene that helps control production of one of these proteins". There are two main types of thalassemia:

Alpha thalassemia in which a gene or genes related to the alpha globin protein are absent or mutated.

Beta thalassemia happens when similar gene hampers the production of the beta globin protein.

Thalassemias are seen among both males and females. The disorders are found most often among people of Middle Eastern, Italian, Greek, Asian, and African descent. Severe forms are mostly diagnosed in early childhood and remain as lifelong condition. Treatments for thalassemias have seen a great improvement in recent years. People who suffer from moderate or severe thalassemias are now having a longer and quality life. However, complications from thalassemias are nor uncommon and their treatments are more frequent. People who suffer from moderate or severe thalassemias must very well follow their treatment plans. They need to take care of themselves in order to remain healthy.

Pyruvate kinase deficiency and sickle cell disease

Comparison

The pyruvate kinase deficiency and sickle cell disease have a common point that is they both are caused due to defect in red blood cell. In both the diseases, damage can happen to the hemoglobin. In pyruvate kinase deficiency the due to the body attacking the red blood cells the hemoglobin is destroyed and in sickle disease the hemoglobin is formed defective. Sickle cell is caused due to hereditary factor and it is passed on from parents to the child whereas in pyruvate deficiency it can be either hereditary or not passed on from parents. There is also similarity in the symptoms of both diseases like fatigue and jaundice. Both the diseases are a pathological condition and require serious treatment. In both the diseases there are chances of occurrence of symptoms in childhood .In both the hemoglobin level can drop down and show anemic condition in the patients. Since the pyruvate deficiency the hemoglobin is destroyed along with red blood cells the hemoglobin level go down and result in anemia in patients. Whereas in sickle cell the cell loses shape and result in anemia.

Differences

The sickle disease is caused by the deformity of red blood cells and the pyruvate deficiency is caused due to the destruction of hemoglobin. So the cause of the disease is due to various reasons. In sickle cell disease the blood cells cluster together and block the blood vessels, whereas in pyruvate deficiency this does not happen as the destruction of red blood cells happen completely and create disease. In sickle cell the person won't suffer from cardiovascular disease unlike pyruvate deficiency. Some times the reason for puyruvate deficiency is unknown but sickle disease happen only because of the deformity in cells. Sickle cell disease is caused by the misshaping of the red blood cells and pyruvate deficiency is caused due to the destruction of red blood cells. Bloom(1995:25)states tha "The large proportion of sickle cell disease cases occur among black, both in Africa and in countries with slave-trading history". But pyruvate deficiency is seen in all races. In sickle cell disease there can be damage to organs of the body and it can turn out fatal but in pyruvate deficiency the cases of death are low.

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