26 public questions tagged with this topic.
In adults, red blood lls are primarily produced in the bone marrow. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Zoology section), Chapter: Structural Organisation in Animals and Frog, Topic: Tissues, skeletal and organ systems.
Hemoglobin, a globular protein, binds oxygen in red blood cells for transport throughout the body.
Ref: NCERT Class 12 Chemistry > Chapter 14: Biomolecules > Topic: Proteins - Structure, Classification and Denaturation
Physiology of carbon dioxide delivery relies on chloride bicarbonate exchange across erythrocyte membrane rather than G protein signaling. Authentic transporter Band 3 anion exchanger 1 SLC4A1 abundant integral protein fourteen transmembrane helices catalyzing electroneutral one to one antiport of chloride for bicarbonate at high turnover supporting conversion of CO2 to bicarbonate via carbonic anhydrase for plasma carriage known as chloride shift Hamburger phenomenon. At pulmonary capillaries exchange reverses enabling CO2 exhalation. GPCR family members are seven-transmembrane receptors coupling to heterotrimeric G proteins generating second messengers cAMP inositol trisphosphate diacylglycerol activating kinases but not transporting chloride as primary mode. Glycophorin major single-pass sialoglycoprotein provides glycocalyx negative charge and pathogen receptor lacking transport activity, spectrin filamentous tetrameric cytoskeletal protein maintains biconcave elasticity lacking ion translocation. Therefore scientifically validated chloride transporter is Band 3 although answer choice listed as GPCR in this dataset reflects probable curation inconsistency noted here, emphasizing need to recognize Band 3 as genuine chloride shift mediator for acid base and gas transport physiology.
Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 15, AE1 Band 3 Chloride-Bicarbonate Exchanger.
Maintenance of biconcave disc shape maximizing surface to volume ratio for deformability and gas exchange depends on membrane skeleton elasticity and organization. Spectrin consists of alpha two hundred eighty kilodalton and beta two hundred forty six kilodalton subunits each containing twenty triple-helical spectrin repeats of one hundred six residues forming elongated flexible anti-parallel heterodimer one hundred nanometers long, two heterodimers associate head to head via helical bundle forming tetramer about two hundred nanometers acting as entropic spring with persistence length about ten nanometers. Tetramers interconnected at junctional complexes comprising thirteen subunit short F-actin filaments capped by adducin and tropomodulin plus protein 4.1R dematin tropomyosin forming pseudohexagonal lattice of about thirty five thousand nodes per cell beneath lipid bilayer. Linkage to bilayer via ankyrin-Band 3 and protein 4.1R-glycophorin C ensures force transmission. Hereditary mutations in SPTA1 encoding alpha spectrin and SPTB encoding beta spectrin cause hereditary spherocytosis and elliptocytosis with fragile cells. GPCR seven-pass signaling and aquaporin channel not structural, confirming spectrin role maintaining biconcave geometry and mechanical elasticity under shear stress circulation.
Ref: Lux and Palek, Erythrocyte Membrane Skeleton and Spectrin Elasticity, Blood Cells.
Detailed topology of glycophorin A major human erythrocyte sialoglycoprotein clarifies single-pass characteristics. Gene GYPA on chromosome four encodes one hundred fifty residues including cleavable signal peptide. Mature protein seventy kilodalton apparent due to extensive glycosylation: seventy residue extracellular domain heavily O-glycosylated fifteen O-linked tetrasaccharides NeuAc alpha2-3 Gal beta1-3 GalNAc plus one N-linked complex chain adding sialic acid dense negative charge defining MNS blood group M and N antigens and preventing rouleaux formation. Hydrophobic anchor residues seventy three to ninety five forms nineteen residue alpha helix containing GXXXG dimerization motif facilitating high affinity dimerization free energy minus twelve kilocalories measured by analytical ultracentrifugation, widely used model for helix-helix interactions. Cytosolic tail thirty six residues acidic interacts with protein 4.1R FERM domain linking to spectrin actin junctional complex near actin protofilament, regulating lateral mobility and mechanosensing. Unlike fourteen-pass Band 3 anion transporter, glycophorin does not transport chloride nor span multiple times nor bind actin directly via actin binding domain, therefore single-pass nature best describes architecture and enables studies of membrane protein folding energetics and Plasmodium invasion receptor function.
Ref: Alberts et al., Molecular Biology of the Cell, 6th ed., Chapter 10, Glycophorin A Structure and Topology.
Human erythrocytes are discoid cells lacking nucleus and organelles, bounded by lipid bilayer containing aquaporin-1 water channels and Band 3 anion exchanger, supported by spectrin-actin cytoskeleton providing elasticity but limited capacity to expand. Cytoplasm osmolarity about 300 milliosmoles dominated by potassium, chloride and hemoglobin remains nearly isotonic with plasma. Placing these cells into hypotonic solution where extracellular solute osmolarity lower than intracellular creates higher extracellular water chemical potential. Water rapidly enters down gradient via aquaporin-1 at billions of molecules per second and to lesser extent through lipid phase, increasing cell volume. Membrane area expands, cell shape transforms from biconcave disc to sphere. Cytoskeletal network stretches. Continued influx beyond roughly 1.4 times normal volume exceeds tensile strength, causing transient ruptures and release of hemoglobin into surrounding medium. Supernatant becomes red, pellet disappears, phenomenon termed hemolysis. In hypertonic solutions opposite efflux shrinks cells producing crenated appearance. No active water pumping compensates, as Na+/K+ ATPase maintains ion gradients slowly but cannot counter immediate osmotic water entry.
Ref: Guyton and Hall, Textbook of Medical Physiology, Chapter 4: Erythrocyte Osmosis and Hemolysis in Hypotonic Solutions.
Erythropoietin, secreted by the kidneys, stimulates the bone marrow to produce red blood cells.
Ref: NCERT Class 11 Biology Chapter 19: Chemical Coordination and Integration Endocrine Disorders
Erythropoietin, secreted by the kidney, stimulates the bone marrow to produce red blood cells.
Ref: NCERT Class 11 Biology Chapter 19: Chemical Coordination and Integration Mechanism of Hormone Action - Second Messengers
Erythropoietin, secreted by the kidneys, stimulates the bone marrow to produce red blood cells.
Ref: NCERT Class 11 Biology Chapter 19: Chemical Coordination and Integration Pancreas - Insulin Glucagon and Diabetes
Erythropoietin, secreted by the kidney, stimulates bone marrow to produce red blood cells.
Ref: NCERT Class 11 Biology Chapter 19: Chemical Coordination and Integration Pineal Gland and Thyroid Gland
Mature RBCs lack a nucleus, which increases their space for hemoglobin and oxygen transport.
Ref: NCERT Class 11 Biology Chapter 15: Body Fluids and Circulation Circulatory System - Comparative and Evolutionary Aspects
Anemia is a condition where there is a deficiency of red blood cells or hemoglobin in the blood.
Ref: NCERT Class 11 Biology Chapter 15: Body Fluids and Circulation Lymph and Circulatory Pathways
