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35 Cards in this Set
- Front
- Back
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What is the function of erythrocytes?
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To transport oxygen from the lungs to the tissue
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Hemoglobin occupies what percentage of the volume of erythrocyte?
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33%
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What percentage of hemoglobin is synthesized before extrusion of the nucleus?
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65%
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Reticulocyte makes up what percentage of hemoglobin for the RBC?
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35%
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What is erythropoiesis? What order does the process proceed in?
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Generation of red blood cells. Hemocytoblast --> proerythroblast --> early erythroblast --> late erythroblast --> normoblast -> reticulocyte --> erythrocyte
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What is tissue switching?
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Where red blood cells are made during development. Switches from yolk sac to liver to bone marrow.
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What does heme do? What is it made up of?
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They oxygen carrying component that also gives blood its color. Contains central iron atom and organic component protoporphyrin.
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Adult Hemoglobin is a multi-subunit protein consisting of what four chains?
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2 alpha globin chains and 2 beta globin chains
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What types of globin chains are found in the normal adult?
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alpha, beta, delta, and gamma
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HbA, HbA2, and HbF are made up of which subunits and make up what percentage of hemoglobin in the adult?
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HbA is 2 alpha and 2 beta and makes up 97%. HbA2 is 2 alpha and 2 delta and makes up 3% and HbF is 2 alpha and 2 gamma and makes up 0.5%
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What chromosome contains the gene for Beta globin?
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Chromosome 11
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What chromosome contains the gene for alpha globin?
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Chromosome 16
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What are the embryonic hemoglobins and when/where are they expressed?
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Hb Gower 1 (zeta 2 epsilon 2), Hb Gower 2 (alpha 2 epsilon 2), Hb Portland (zeta 2 gamma 2). Expressed in yolk sac but not after 8 weeks of age.
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What is fetal hemoglobin and when/where is it expressed?
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HbF (alpha 2 gamma 2). Made in the liver and is the primary hemoglobin for the fetus.
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When does the level of HbA reach adult levels in a newborn child?
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After 1 year of life. Production of HbA starts immediately after birth, though.
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_______ infants switch later after birth to adult Hb than do _______ babies.
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Premature.
Full term |
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What is sickle cell anemia?
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Substitution at position #6 in beta globin of valine for glutamic acid which causes polymerization of hemoglobin and sickling of RBC's.
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Why is sickle cell anemia a problem?
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The sickle shape of the RBC's impedes circulation and can cause pain, organ damage, strokes, increased infections, etc.
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What can be done to help sickle cell patients?
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Induce HbF.
Currently use hydroxyurea to induce HbF, but that is a chemotherapeutic agent. Currently researching ways to induce HbF expression. |
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What is protoporphyrin?
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Organic component of heme made up of four pyrrole rings which contain the iron atom bonded to the pyrrole nitrogens.
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The F8 histidine is called the _______ histidine which is bound to the heme group.
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Proximal
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The E7 histidine is called the ________ histidine and oxygen binds to the iron between the heme and this histidine.
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Distal
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How does the binding of oxygen cause a conformational change?
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The iron atom initially exists outside the plane of the porphyrin and when oxygen binds it pulls the F8 proximal histidine, which is attached to the globin chain. This causes a change in the interaction of the globin chains.
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What is myoglobin and how does it differ from hemoglobin?
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Myoglobin is a monomer encoded by a different gene. Only contains one heme-iron and acts as an oxygen storage protein instead of an oxygen transport protein.
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What are the shapes of the curves for myoglobin and hemoglobin on an oxygen dissociation curve? Why are they shaped that way?
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Myoglobin is hyperbolic - myoglobin only binds and stores oxygen so at higher partial pressures the saturation is maximal (high affinity all the time)
Hemoglobin is sigmoidal - switches between high and low affinity in order to bind oxygen in the lungs and deposit it in the tissue. |
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What is positive cooperativity?
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When one molecule of oxygen binds to Hb it facilitates the binding of another at a different heme due to the conformational change it undergoes.
"Appetite of Hb for oxygen grows with eating." This process also holds true in reverse! When one oxygen is lost it's easier to lose another. |
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What are the modulators of Hb function?
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2,3-BPG, hydrogen, HbF
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What is 2,3-BPG and What effect does 2,3-BPG have on hemoglobin?
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A byproduct of glycolysis; signals Hb to release oxygen.
2,3-BPG reduces affinity and it is produced in respiring cells that need the oxygen. Shifts ODC curve to the RIGHT |
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What is the Bohr Effect?
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Binding affinity of Hb for oxygen decreases as pH decreases.
pH of actively respiring tissues is lower, favors release of oxygen |
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How does HbF act as a modulator for HbA?
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HbF has a higher affinity for oxygen so oxygen flows from mom to fetus.
Hbf does not bind well to 2,3-BPG, and therefore has a higher affinity for oxygen. Shifts ODC to the LEFT. |
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What are the two forms that hemoglobin can exist in?
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Tense and Relaxed form.
T is low affinity (beta chains further apart) and R is high affinity (beta chains closer together). |
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What does 2,3-BPG do to the T form?
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Stabilizes the T state by binding in the deoxy Hb.
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True or false: An equilibrium exists between the T and R states at each level of oxygen loading?
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True.
Shifts from strongly favoring T state with no oxygen bound to strongly favoring the R state when fully loaded with oxygen. |
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The bond with _______ and Hb is 210 times stronger than the bond with oxygen.
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Carbon monoxide.
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What is HbA1c?
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Post translational modification of glucose with the N terminus of the B globin chain.
Increased in diabetes by 2x - 3x, reflects the control of glucose for the last 120 days and is used to measure the adequacy of diabetic control. |
