RBCs Flashcards
Red blood cells
Specialized cells of the blood, function to carry O2 to tissues and carry CO2 away from tissues
What are the features of the RBCs that aid their function?
Bi-concave shape
Lack of organelle
Metabolic function
How are RBCs formed (erythropoiesis)?
Lack of O2 in tissues triggers the kidney to release a hormone erythropoietin (EPO)
EPO travls to the bone marrow and induces erythrocyte progenitor cells the multiply and differentiate into RBCs
What are reticulocytes?
Young RBCs which which will still contain some organelles (mRNA, ribosomes, golgi)
24-48 hrs to mature
If there in an inc in a reticulocyte count what could that indicate?
Chronic bleeding or hemolytic anemia
If there in a dec in reticulocyte count what could that indicate?
Pernicious anemia or bone marrow dysfunction
What does the biconcave shape do for the RBC?
Gas-exchange: max surface/volume ratio
Deformable: can move in capillaries
Survival in various osmotic pressure, room to swell
Spherocytosis
Deformity in RBCs which leaves them spherical instead of biconcave
Results in anemia
What the content make up of an RBC membrane?
50% lipid, 50% protein
What are the lipids of the RBC membrane?
Cholesterol and phospholipid (PC, PE, PS, Sph)
What are the major phopholipids comprising the RBC membrane?
Phosphatidylethanolamine (PE)
Phosphatidylcholine (PC)
Phosphatidylserine (PS)
Sphingomyelin (Sph)
Which phosphates predominate in the out leaflet of the RBC bilayer?
Sph and PC
What are glycoproteins and what amount of the total RBC lipid are they?
Factors comprising ABO blood groups
5-10%
What are the most well known blood type groups?
ABO and Rb
What is a blood group?
Antigens on the external surface of RBCs
What are ABO substances comprised of?
Complex oligosaccharides
If an allele codes for glycosyltransferase what blood type must that person have?
A or B
O is the deletion of the gene
What are the key proteins in and around the RBC membrane?
Spectrin, ankyrin, band 3 (anion exchange protein), glycophorins, 4.1
What is the main function of Band 3?
Chloride-bicarbonate exchanger of the cell
Anchors to membrane skeleton by ankyrin
Regulation of ion content, deforms cell, metabolism
What are the functions of glycophorin?
Largest component of integral membrane proteins
High sialic acid content (surface charge)
Stability of membrane, deform cell, shape
What are the functions of ankyrin?
Pyramid-shaped
Binds to band 3 and spectrin
Maintain cell shape
What are the functions of 4.1?
Contain spectrin-actin binding site
Linkage of spectrin-actin membrane skeleton to lipid bilayer via linkage to band 3 and glycophorins
Membrane deformability and resilience
What is spectrin and what does it do?
Peripheral membrane protein, comprise of alpha and beta heterodimers
Modulation of cell shape
What are the protective enzymes in RBCs?
Superoxide dimutase (transition of ROS) Catalase (H2O2 to O2 and H2O) Glutathione reductases (GSSG to GSH)
What is methemoglobin (metHb) form by?
Auto-oxidation of Fe2+ in hemoglobin to Fe3+
What is the problem with metHb?
Can’t transport oxygen
How do RBCs change from metHb to normal Hb?
NADH-cytochrome b5 metHb reductase system (off-shoot of glycolysis)
How could someone have a metHb anemia?
Inherited - deficiency of cytochrome reductase or others
Acquired - ingestion of chemicals (sulfanoamides/anilines)
How are metHb anemias treated?
Administering oral or IV of methylene blue or ascorbic acid
What is the importance of the hexose monophosphate shunt?
Generates NADPH by glucose that is moved in
Maintains glutathione in reduced state (GSH)
Which step in glycolysis can cause anemia if deficient?
G6PD
What is the importance of the Rapoport-Luberin shunt?
Generates 2,3-bisphosphoglycerate
Can moderate the binding of O2 to Hb
Heme
4 polypeptide chains surrounding a porphyrin ring
Describe heme synthesis
Start with succinyl Co-A, condenstation of the pyrrole rings
What are porphyrias?
Diseases resulting from errors in here metabolism
Typically genetic
How is heme degraded?
Globins are recycled by making heme into bilirubin and is then transported to the liver and excreted as bile
How can you fix jaundice in newborns?
Phototherapy