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What is formed when haemoglobin is oxidized from Fe2+ to Fe3+?
What is formed when haemoglobin is oxidized from Fe2+ to Fe3+?
NADH methaemoglobin reductase deficiency is common in individuals.
NADH methaemoglobin reductase deficiency is common in individuals.
False
What anticoagulant is used when preparing blood samples for a full blood count?
What anticoagulant is used when preparing blood samples for a full blood count?
Ethylenediaminetetraacetic acid (EDTA)
The presence of inclusions within blood cells can be observed in a __________ blood film.
The presence of inclusions within blood cells can be observed in a __________ blood film.
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Match the following blood parameters with their descriptions:
Match the following blood parameters with their descriptions:
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What transports iron molecules to tissues with transferrin receptors?
What transports iron molecules to tissues with transferrin receptors?
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Haemosiderin is a water-soluble compound that stores iron.
Haemosiderin is a water-soluble compound that stores iron.
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What is the primary risk associated with iron overload?
What is the primary risk associated with iron overload?
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Haem is an iron-containing derivative located at the center of the __________ ring.
Haem is an iron-containing derivative located at the center of the __________ ring.
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Which condition is characterized by excessive intestinal absorption of iron?
Which condition is characterized by excessive intestinal absorption of iron?
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Match the following iron storage proteins with their properties:
Match the following iron storage proteins with their properties:
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The iron ion in haem is located in the protoporphyrin IX structure.
The iron ion in haem is located in the protoporphyrin IX structure.
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Degradation of haem takes place in the __________ of the spleen, bone marrow, and liver.
Degradation of haem takes place in the __________ of the spleen, bone marrow, and liver.
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What is the primary structure of adult hemoglobin (HbA)?
What is the primary structure of adult hemoglobin (HbA)?
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Myoglobin provides an oxygen reserve primarily in muscle tissue.
Myoglobin provides an oxygen reserve primarily in muscle tissue.
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What chromosome contains the genes encoding the ε-, γ-, σ- and β- chains of hemoglobin?
What chromosome contains the genes encoding the ε-, γ-, σ- and β- chains of hemoglobin?
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Each hemoglobin molecule can bind _____ molecules of oxygen.
Each hemoglobin molecule can bind _____ molecules of oxygen.
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Match the globin chains with their respective chromosomes:
Match the globin chains with their respective chromosomes:
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What shifts the position of the hemoglobin dissociation curve?
What shifts the position of the hemoglobin dissociation curve?
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Binding of one O2 molecule decreases the affinity for oxygen at the remaining haem groups.
Binding of one O2 molecule decreases the affinity for oxygen at the remaining haem groups.
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What configuration of hemoglobin occurs when it is oxygenated?
What configuration of hemoglobin occurs when it is oxygenated?
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What is the average lifespan of red blood cells?
What is the average lifespan of red blood cells?
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Red blood cells are nucleated and contain organelles.
Red blood cells are nucleated and contain organelles.
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What primary function do erythrocytes serve?
What primary function do erythrocytes serve?
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The majority of carbon dioxide is transported in the blood as __________.
The majority of carbon dioxide is transported in the blood as __________.
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Which hormone regulates erythropoiesis?
Which hormone regulates erythropoiesis?
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The total iron store in the body is primarily found as hemoglobin.
The total iron store in the body is primarily found as hemoglobin.
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Match the following forms of carbon dioxide transport with their corresponding percentages:
Match the following forms of carbon dioxide transport with their corresponding percentages:
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Erythropoietin is primarily secreted by the __________ in the renal cortex.
Erythropoietin is primarily secreted by the __________ in the renal cortex.
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What effect does sickle-cell haemoglobin have on the oxygen dissociation curve?
What effect does sickle-cell haemoglobin have on the oxygen dissociation curve?
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Dysfunction in integral proteins is the basis of some inherited diseases that result in anaemia.
Dysfunction in integral proteins is the basis of some inherited diseases that result in anaemia.
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What is the net yield of ATP molecules produced from the glycolytic pathway in red blood cells?
What is the net yield of ATP molecules produced from the glycolytic pathway in red blood cells?
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The glycolytic pathway metabolizes glucose to ______.
The glycolytic pathway metabolizes glucose to ______.
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Match the following proteins with their classification:
Match the following proteins with their classification:
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What is produced in the hexose monophosphate shunt for every molecule of glucose-6-phosphate?
What is produced in the hexose monophosphate shunt for every molecule of glucose-6-phosphate?
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Inherited diseases linked to the cytoskeleton of red blood cells include hereditary spherocytosis and hereditary elliptocytosis.
Inherited diseases linked to the cytoskeleton of red blood cells include hereditary spherocytosis and hereditary elliptocytosis.
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What key component anchors many surface proteins to the erythrocyte membrane?
What key component anchors many surface proteins to the erythrocyte membrane?
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Study Notes
Red Blood Cells and Haemoglobin
- Red blood cells (erythrocytes) have a lifespan of 120 days
- Normal erythrocyte concentration in blood is 3.9-6.5 x 1012/L
- They lack a nucleus and organelles
- Contain millions of haemoglobin molecules, a red oxygen-carrying pigment
- Have a biconcave disc shape, providing a larger surface area than a sphere of the same volume
- Primary function is carrying oxygen (O2) and carbon dioxide (CO2) between lungs and tissues
- Also involved in pH buffering
Erythrocyte Function
- The primary function is O2 and CO2 transport between the lungs and tissues
- The large surface area facilitates this function
- pH buffering is also a function
Gas Exchange and Transport
- 1000 ml of O2 is transported by haemoglobin (Hb) per minute. Most O2 is transported by Hb, with small amounts dissolved in plasma
- O2 content of the blood depends on:
- Hb concentration
- Hb affinity for O2
- O2 solubility in the blood (minor effect)
CO2 Transport
- CO2 is transported in three forms:
- ~90% as bicarbonate
- ~5% as carbamino compounds (combining with plasma proteins and haemoglobin)
- ~5% in physical solution (CO2 is significantly more soluble in blood than O2)
Electrolytes Balance
- Chloride, potassium, and hydrogen ions are transported across the red cell membrane
- In stored blood, extracellular potassium levels are high due to disrupted active transport
Erythropoiesis
- Erythropoiesis is the production of red blood cells in bone marrow
- This process starts with a pronormoblast, progressing through early, intermediate, and late normoblasts to reticulocytes, and finally to erythrocytes
- There are progressive changes in cell appearance and increasing amounts of haemoglobin in each stage
Regulation of Erythropoiesis
- Erythropoietin (EPO) is the hormone that regulates erythropoiesis
- It's a heavily glycosylated polypeptide
- 165 amino acids long, weighing 30,400 kDa
- Mainly produced by endothelial cells in the renal cortex (90%) and by Kupffer cells and hepatocytes in the liver (10%)
Control of Erythropoietin Drive
- Hypoxia is the primary stimulus for EPO secretion
- Any factor decreasing oxygen transport to tissues compared to demand can trigger EPO production
Iron Metabolism
- Total iron storage in the body is approximately 4g, mainly as haemoglobin
- Daily iron requirement is about 1 mg
- Iron absorption is controlled by proteins in the gut
- Iron transfer rate from epithelial cells to plasma depends on iron requirements, being highest when iron stores are low or erythropoiesis is high
Haem Metabolism
- Haem is part of a porphyrin family, characterized by a tetrapyrrole ring
- Haem contains an iron ion (Fe2+) at the centre of the protoporphyrin IX ring, vital for haemoglobin's oxygen-binding properties
Haem Biosynthesis
- Haem synthesis occurs in the mitochondria of immature red blood cells in the bone marrow
- The process is outlined in the provided figure
Haem Breakdown
- Haem breakdown occurs in macrophages within the spleen, bone marrow, and liver
Haemoglobin
- Haemoglobin (Hb) is composed of four globin chains held together by non-covalent interactions
- Each globin chain has a hydrophobic pocket containing the haem molecule
- Hb can carry four oxygen molecules
- Different types of haemoglobin exist during development, having different chain combinations
Genetics of Haemoglobin
- Genes encoding haemoglobin chains ε, γ, δ, and β are located on chromosome 11, while genes for the α-chains are on chromosome 16
- Each globin gene contains three exons and two introns
- Globin chains are synthesized separately and assemble to form functional haemoglobin
Physiological Properties of Haemoglobin
- One oxygen molecule binding to Hb increases the affinity of remaining haem groups for oxygen, causing a sigmoidal oxygen dissociation curve
- CO2, H+, 2,3-DPG, and temperature affect the oxygen dissociation curve position, but not the shape
- Haemoglobin variants can alter the oxygen dissociation curve position, e.g. sickle cell haemoglobin
Oxygen Dissociation Curve
- A plot of partial oxygen pressure (x-axis) against oxygen saturation (y-axis)
- Shows the relationship between oxygen pressure and haemoglobin's ability to bind oxygen
Metabolism of Red Cells
- Glycolysis (Embden-Meyerhof pathway) is the main glycolytic pathway in red blood cells, metabolizing glucose to lactate
- This pathway produces 2 ATP molecules per glucose molecule, with no net NADH production
- The hexose monophosphate shunt (HMP) is an oxidative pathway in red blood cells and accounts for ~5% of glucose metabolism, producing two NADPH molecules per glucose-6-phosphate entering the shunt
Prevention of Haem Oxidation
- Haemoglobin oxidation (Fe2+ to Fe3+) forms methaemoglobin, which reduces oxygen-carrying capacity
- Excess methaemoglobin can be caused by toxic substances or abnormal haemoglobin types, or NADH methaemoglobin reductase deficiencies
Full Blood Count and Reticulocyte Count
- Blood samples are treated with EDTA (anticoagulant)
- Automated analysers provide data like haemoglobin concentration, haematocrit, red blood cell count, mean cell volume (MCV), mean cell haemoglobin (MCH), mean cell haemoglobin concentration (MCHC), white blood cell count (with differential), platelet count, and red cell distribution width (RDW)
Peripheral Blood Film
- Examination of a peripheral blood film shows the morphology of blood cells and any inclusions
Normal Red Blood Cells
- Normal red blood cells typically measure less than 7.2 µm in diameter and have a central pallor reflecting their biconcave shape. Platelets are small, irregular, and densely staining
Red Blood Cell Abnormalities
- Various red blood cell abnormalities on peripheral blood films are described, with diagnostic inferences. (e.g., anisocytosis, poikilocytosis, spherocytes, sickle cells etc.)
Red Blood Cell Cytoskeleton
- The erythrocyte plasma membrane is supported by a cytoskeleton (a dense, fibrillar protein shell)
- Maintaining cell shape, strength, and flexibility is critical for the erythrocyte's role in circulation
- The key structural proteins (integral and peripheral) of the red blood cell cytoskeleton are described. (e.g., Band 3, glycophorins, spectrin, ankyrin, 4.1 protein, actin)
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Description
This quiz covers essential information about red blood cells and their primary component, haemoglobin. Topics include the structure, lifespan, and function of erythrocytes, as well as their role in gas exchange and buffering pH levels in the body. Test your understanding of these vital processes in human physiology.
