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Questions and Answers
At which stage of erythrocyte development do cells start to fill with hemoglobin?
At which stage of erythrocyte development do cells start to fill with hemoglobin?
What is the primary function of hemoglobin in erythrocytes?
What is the primary function of hemoglobin in erythrocytes?
What percentage of carbon dioxide is transported by erythrocytes?
What percentage of carbon dioxide is transported by erythrocytes?
How do reticulocytes enter the blood stream?
How do reticulocytes enter the blood stream?
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What is the typical concentration of reticulocytes among red blood cells?
What is the typical concentration of reticulocytes among red blood cells?
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What is the name of the stage where the cell still has remnants of organelles and ribosomal RNA?
What is the name of the stage where the cell still has remnants of organelles and ribosomal RNA?
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How long does it take for the remaining material in reticulocytes to disappear?
How long does it take for the remaining material in reticulocytes to disappear?
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What is the primary function of erythrocytes?
What is the primary function of erythrocytes?
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What is the primary function of the proteins in red blood cells?
What is the primary function of the proteins in red blood cells?
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What is the average lifespan of human erythrocytes in the circulation?
What is the average lifespan of human erythrocytes in the circulation?
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Where are primitive nucleated red blood cells produced during embryonic development?
Where are primitive nucleated red blood cells produced during embryonic development?
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What is the primary site for RBC production in the middle trimester of pregnancy?
What is the primary site for RBC production in the middle trimester of pregnancy?
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What is the primary function of macrophages in the spleen, liver, and bone marrow?
What is the primary function of macrophages in the spleen, liver, and bone marrow?
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What type of stem cell gives rise to RBCs after birth?
What type of stem cell gives rise to RBCs after birth?
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What is the result of abnormalities in the proteins that form the lattice on the inside of the cell membrane?
What is the result of abnormalities in the proteins that form the lattice on the inside of the cell membrane?
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What is the first cell in the RBC series formed from CFU-E stem cells with appropriate stimulation?
What is the first cell in the RBC series formed from CFU-E stem cells with appropriate stimulation?
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What is the primary advantage of the biconcave shape of erythrocytes?
What is the primary advantage of the biconcave shape of erythrocytes?
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What is the function of carbonic anhydrase in erythrocytes?
What is the function of carbonic anhydrase in erythrocytes?
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Why do erythrocytes not consume oxygen during transport?
Why do erythrocytes not consume oxygen during transport?
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What is the primary source of energy for erythrocytes?
What is the primary source of energy for erythrocytes?
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What is the function of the Embden-Meyerhof pathway in erythrocytes?
What is the function of the Embden-Meyerhof pathway in erythrocytes?
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What happens to hemoglobin when it is oxidized?
What happens to hemoglobin when it is oxidized?
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What is the effect of an increased count of erythrocytes in the blood?
What is the effect of an increased count of erythrocytes in the blood?
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What happens to glucose that enters the red blood cell from plasma?
What happens to glucose that enters the red blood cell from plasma?
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What is the primary function of the protein spectrin in red blood cells?
What is the primary function of the protein spectrin in red blood cells?
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What is the approximate diameter of red blood cells?
What is the approximate diameter of red blood cells?
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What is the advantage of the biconcave shape of red blood cells?
What is the advantage of the biconcave shape of red blood cells?
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What is the normal concentration of erythrocytes in the blood of women?
What is the normal concentration of erythrocytes in the blood of women?
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What is the purpose of the flexibility of the protein net in red blood cells?
What is the purpose of the flexibility of the protein net in red blood cells?
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What is the term for the process of red blood cells becoming cup-shaped as they pass through capillaries?
What is the term for the process of red blood cells becoming cup-shaped as they pass through capillaries?
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What is the function of the plasma membrane in red blood cells?
What is the function of the plasma membrane in red blood cells?
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What is the term for the cells from which red blood cells develop?
What is the term for the cells from which red blood cells develop?
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What is the primary function of the Luebering–Rapoport shunt in erythrocytes?
What is the primary function of the Luebering–Rapoport shunt in erythrocytes?
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What is the consequence of glucose-6-phosphate dehydrogenase (G6PD) deficiency in erythrocytes?
What is the consequence of glucose-6-phosphate dehydrogenase (G6PD) deficiency in erythrocytes?
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What is the primary function of NADPH generated in the hexose monophosphate shunt?
What is the primary function of NADPH generated in the hexose monophosphate shunt?
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What is the percentage of glycolysis that occurs through the hexose monophosphate shunt?
What is the percentage of glycolysis that occurs through the hexose monophosphate shunt?
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What is the end product of the hexose monophosphate shunt?
What is the end product of the hexose monophosphate shunt?
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What is the role of glutathione in the erythrocyte?
What is the role of glutathione in the erythrocyte?
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Study Notes
Hemoglobin Production
- Hemoglobin production starts in polychromatophil erythroblasts
- In successive generations, cells fill with hemoglobin, and the nucleus and endoplasmic reticulum are reabsorbed
- The cell at this stage, called a reticulocyte, still has remnants of organelles and ribosomal RNA, allowing it to produce hemoglobin
Reticulocyte Stage
- Reticulocytes pass from the bone marrow to the blood capillaries via diapedesis
- Within 1-2 days, the remaining material disappears, and the cell becomes an erythrocyte
- Reticulocyte concentration among red blood cells is usually less than 1%
Functions of Red Blood Cells
- Gas transport function: Red blood cells transport respiratory gases like oxygen and carbon dioxide
- Hemoglobin, a protein in these cells, binds with oxygen and most oxygen in the blood is carried by it
- Red blood cells pick up oxygen in the lungs and deliver it to tissue cells in the body, and also transport about 20% of carbon dioxide back to the lungs
- Erythrocytes have three structural characteristics that help them transport gases effectively:
- Small size and biconcave shape provide a huge surface area relative to volume (about 30% more surface area than comparable spherical cells)
- Discounting water content, an erythrocyte is over 97% hemoglobin, the molecule that binds to and transports respiratory gases
- Because erythrocytes lack mitochondria and generate ATP by anaerobic mechanisms, they do not consume any of the oxygen they are transporting, making them very efficient oxygen transporters
Structural Characteristics
- Erythrocytes or red blood cells (RBCs) are small, anucleate cells enclosed by a plasma membrane and shaped like biconcave discs with depressed centers
- They are about 7.5μm in diameter and maintain their shape through a network of proteins, particularly spectrin
- The biconcave shape provides a large surface-to-volume ratio and facilitates gas exchange
- The normal concentration of erythrocytes in the blood is approximately 3.9 to 5.5 million per microliter (μL, or mm3) in women and 4.1-6.0 million/μL in men
Maturation and Development
- Several proteins in red blood cells are important in maintaining their shape
- These include band 3, proteins 4.1, 4.2, α and β spectrin, ankyrin, protein 4.1, and actin
- Together, they form a lattice on the inside of the cell membrane
- Spectrin is the most abundant protein
- Abnormalities in these proteins can result in red blood cells with an unusual shape, such as hereditary spherocytosis and elliptocytosis
Red Cell Metabolism
- In this series of biochemical reactions, glucose that enters the red cell from plasma by facilitated transfer is metabolized to lactate
- For each molecule of glucose used, two molecules of ATP and thus two high‐energy phosphate bonds are generated
- This ATP provides energy for the maintenance of red cell volume, shape, and flexibility
- The Embden–Meyerhof pathway also generates NADH, which is needed by the enzyme methemoglobin reductase to reduce functionally dead methemoglobin containing ferric iron to functionally active, reduced hemoglobin containing ferrous ions
Origin of Blood
- The Luebering–Rapoport shunt, or sidearm, of this pathway, generates 2,3‐DPG, important in the regulation of hemoglobin’s oxygen affinity
- Hexose monophosphate shunt:
- Approximately 10% of glycolysis occurs by this oxidative pathway in which glucose‐6‐phosphate is converted to 6‐phosphogluconate and so to ribulose‐5‐phosphate
- NADPH is generated and is linked with glutathione which maintains sulphydril (SH) groups intact in the cell, including those in hemoglobin and the red cell membrane
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Description
Learn about hemoglobin production from polychromatophil erythroblasts to reticulocytes and the process of diapedesis. Understand the stages and characteristics of reticulocyte development.
