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Lecture 3

Lecture 3 – development of red blood cells.docx

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Biological Sciences
Ian Brown

Lecture 3 – development of red blood cells The first row consists of reptiles, birds and fish. The red blood cells are ovular in shape and have dark structures within them (condensed nucleus) The bottom row consists of red blood cells of cats, dogs, and humans. The red blood cells don’t contain a nucleus and is rounded structure. It has no nucleus in order to make more space to pack in protein (hemoglobin) (slide 3) Lecture 3 – development of red blood cells Human RBC erythrocyte – mature red blood cell They have a diameter of 6 – 7.5 μm and they are 2.0 μm wide (thick) and they have a disk shape Human red blood cells don’t contain organelles such as mitochondria but has plasma membrane packed with hemoglobin cytoskeleton (95%) The red blood cell is one of the smallest cells in the human body RBCs are very small and flexible and this is required for them to be able to pass through blood vessels (such as the capillaries) Lecture 3 – development of red blood cells Dark blob is the protein actin The line is the protein spectin Lecture 3 – development of red blood cells Carry away CO2 (by-product of cellular respiration) Cellular respiration generates ATP (energy) and is needed for the body to function Hemoglobin is used to transport oxygen Oxygen binds to the heme group in hemoglobin molecules Lecture 3 – development of red blood cells In each hemoglobin there are 4 subunits and each subunit has a heme group since there are four irons in one hemoglobin, one hemoglobin will be able to carry 4 oxygen molecules in total Lecture 3 – development of red blood cells Macrophage detects RBC age possibly by …. Cell rigidity? As RBC ages there is an increase in calcium levels in the cytoplasm The increased calcium level activates calpain and calpain cleaves spectrine This causes the cell to become rigid The macrophage senses cell rigidity and then engulfs the cell (Phosphatidylserine moves from inner phase to outer phase) Lecture 3 – development of red blood cells When hemoglobin is released from aged RBC most components are recycled Iron will be stored macrophage or released in bloodstream and binds to transferrin, it may also be absorbed by red bone marrow (site of RBC production) Heme enzyme in macrophage causes heme to convert into biliverdin then bilirubin It is then transported to the liver then to the small intestine The bacteria causes bilirubin to be converted into urobilinogen Urobilinogen moves into the colon and gives color to waste Globin protein subunits  amino acid are produced by globin protein They are broken down my macrophages and some a released into the blood stream and are then recycled 1. Note that the stem cell had no hemoglobin 4. marker proteins can indentify changes in globin levels . mRNA can also be used to control at what stage the globin molecules will be turned on 6. RBC production development occurs all through life 7. Transgenic animal variation can be used to see the norman pattern vs the defects in globin development Lecture 3 – development of red blood cells Location of RBC development site depends on the age. Adults – red marrow Red marrow is found throughout long bones (earlier stages) in the adult long bone the red marrow is only found at the ends Birds and reptiles have a large yold sac (develop externally (egg)) on the other hand energy resource for mammals such as humans obtain energy from he placenta (mother). Mammals also have yolk sacs but it is external to the embryo (extra- embryonic) – it acts as a circulatory system Lecture 3 – development of red blood cells Colonization theory – Stem cells leave one area and colonize another by entering the blood stream (this is how erythropoiesis switch location) (slide 22) Lecture 3 – development of red blood cells The 2 alpha (α) genes are found on chromosome 16. Since humans are diploid organisms (they have to sets of genes) they have 4 alpha globin genes. Beta Globin Gene Cluster Is found on chromosome 11 There are 3 types (gamma - ϒ, delta - Δ, and beta - β)
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