Covers red blood cells: their structure as anucleate biconcave cells, lifespan of about 120 days, and energy metabolism. It then moves to haemoglobin's quaternary structure, oxygen and carbon monoxide binding, and the ABO blood groups defined by surface antigens and antibodies. The note also traces haem breakdown to bilirubin and urobilin, lists iron, erythropoietin, vitamin B12 and folic acid needed for haemoglobin synthesis, and ends with erythropoiesis regulation by hypoxia.
Topic 15 of 104 in the MU Sofia syllabus for Physiology (Dental Medicine, Year 2). The free AceMed note covers it in 1 section, about 572 words (4 min of reading), with 20 flashcards.
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Introduction
Introduction
Erythrocytes (red blood cells or RBCs) are anucleate, biconcave cells, filled with hemoglobin, that transport oxygen and carbon dioxide between the lungs and tissues. They are produced in the red bone marrow by a process called erythropoiesis. During this process, stem cell derived erythroid precursors undergo a series of morphological changes to become mature erythrocytes.
Last for around 120 days.
Are destroyed by phagocytosis in Liver, Spleen and Bone marrow.
Number of erythrocytes per litre blood around 4,2 to 5,4 x 1012/L.
Mature erythrocyte lacks Nucleus and Mitochondria. Since they lack mitochondria they have anaerobic (no oxygen) respiration for energy. Mainly glucose for energy
Haemoglobin
Haemoglobin is a protein with quaternary structure because it has four polypeptide chains bound together, two α-chains and two β-chains. Each chain, or Haem, has one Iron atom in the middle. Oxygen binds to the Iron atom in the haem. About 95% of the dry weight of an erythrocyte is the Haemoglobin proteins. Amino acids and Iron atom are needed for haemoglobin synthesis.
To the Iron atom oxygen will bind reversibly in the lungs. So 4 Iron atoms means 4xO2 to haemoglobin protein. Oxygen has 95% saturation which causes the high affinity for haemoglobin. Carbon monoxide (CO) has higher affinity than oxygen which is the reason for it being toxic and lethal to humans, because CO will occupy all Iron atoms and oxygen can’t bind.
Blood types The blood type is determined by the carbohydrate antigens on the surface (glycocalyx) of erythrocytes. Because those antigens determine which antibodies will be present in our bloodstream and cause clumping by IgM.
Blood group A: having antigen-A on the erythrocytes makes it produce anti-B.
Blood group B: having antigen-B makes the body produce anti-A.
Blood group O: having no antigens on erythrocytes and producing both anti-A & anti-B.
Blood group AB: has both antigen-A & antigen-B present on surface so no antibodies are produced.
Er contain hemoglobin, an iron-containing protein,which is able to bind reversibly O2 and CO2.
The Er are destroyed by macrophages in the spleen, liver and marrow.
The heme is broken down to Fe3+ and biliverdin (a greenish pigment), which is reduced to bilirubin.
Bilirubun is transported by a plasma protein to the liver, where it is joined to glucuronic acid and secreted in the small intestine.
Intestinal bacteria convert bilirubin to urobilinogen.
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