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Hemoglobin
68K 12-01 Hemo 101 Unit 2
36
Other
Undergraduate 2
01/11/2012

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Term
What is Hemoglobin?
Definition
protein, main cytoplasmic component of erythrocytes. Oxygen carrying componet of the RBC
Term
Functions of Hemoglobin
Definition
MAintain homeostasis by facilitating cellular respiration.
Delivers oxygen to tissues from lungs.
Pulls CO2 away from tissues.
Balances pH.
Term
Oxygen Delivery
Definition
Hgb is able to do this because it can reversibly bind with oxygen, Hgb picks up O2 in the lungs and transports it via the RBCs to the oxygen-poor tissues where it releases O2.
Term
Pulls Carbon Dioxide Away
Definition
Hgb can do this because of its ability to bind gases of cellular waste, picks up CO2 from tissues and transports it to the lungs to be exhaled.
Term
Maintaining Acid Base
Definition
Hgb contributes to the bicarbonate buffer system by binding or releasing Hydrogen atoms.
Term
When blood pH rises...
Definition
More alkaline, CO2 combines with water to produce carbonic acid allow hydrogen ions to be released and causes pH to decrease.
Term
When blood pH drops...
Definition
more acidic, carbonic acid dissociates to release hydrogen and bicarbonate, blood pH raises. Bicarbonate travels to the lungs to be exhaled.
Term
Basic Hemoglobin Structure
Definition
4 heme groups, 2 pairs of unlike polypeptide chains.
Protein with a non protein.
Term
Heme Composition
Definition
Protoporphyrin Ring (carbon, hydgrogen, nitrogen), atom of ferrous iron, each heme is positioned in a pocket of the polypetide chain, site of oxygen binding.
Term
Gobin Composition
Definition
2 pairs of unlike polypeptide chain, bracelets of amino acids linked together.
Term
Polypeptide chain types
Definition
comprised of 141-146 amino acids each, sequence and number is determined by structural genes, variations give rise to different types of polypeptide chains.
Term
Hemoglobin synthesis
Definition
occurs during RBC development, ends in the reticulcyte stage.
Term
Heme synthesis
Definition
occurs in the mitochondria of the RBC precursor, iron is transported in the primiteve rBC and proceeds to the mitochondria, iron combines with Protoporphyrin IX.
Term
Globin Synthesis
Definition
occurs in the ribosomes, using mRNA they are translated into polypeptide chains.
Term
How do Heme and Globin come together?
Definition
each globin chain pairs off with a heme once released from the ribosome, an aglobin and a non-aglobin binds forming a heterodimer, 2 heterodimes combine to form a tetramer.
Term
Hemoglobin Structure After Synthesis
Definition
tetrameric molecule. 4 polypeptide chains : 2 A globin, 2 non A globin/ 4 Heme groups: 1 heme per polypetide, has the ability to carry ONE oxygen. an average RBC contains 640 million tetramers.
Term
HEmoglobin types
Definition
Hemoglobin A - 2a and 2 b
Hemoglobin A2 - 2a and 2 d
Hemoglobin F - 2a and 2 Gamma
Term
Oxyhemoglobin
Definition
Molecule fully saturated with oxygen, carries oxygen from the lungs to the tissues.
Term
Deoxyhemoglobin
Definition
returing to the lungs with CO2 from tissues. O transport is based on the affinity for Hgb to bind oxygen.
Term
Increased Oxygen Tension (^pO2)
Definition
Oxygen tension is high inside the lungs, Hgb has a higher affinity for oxygen, O2 Molecule binding increses the affinity allowing Hgb to be completely oxygenated, resulting in oxyhemoglobin.
Term
Decreased Oxygen Tension (downpO2) or (^pCO2)
Definition
oxygen tension is low inside the tissues, Hgb has less affinity for oxygen where tension is low, allows O2 to be released, resulting in deoxyhemoglobin.
Term
Bohr Effect
Definition
any of the following causes Hgb to bind to O with less affinity:
^ in blood Co2
Decrease in pH
^ in 2,3-DPG
^ in temperature
Term
Bohr Effect and CO2
Definition
Increased CO2 results in decreased Hgb Affinity for oxygen
Term
Bohr Effect and pH
Definition
When pH falls, Hgb loses its affinity for oxygen, it lowers due to the presence of lactic acid and CO2, facilitates the release of oxygen to tissues.
When pH rises, Hgb gains an affinity for oxygen, faicilates the release of CO2 and the binding of oxygen.
Term
Bohr Effect and 2,3-DPG
Definition
2,3-dpg binds deoxyhemoglobin, and acts to stabilize the molecule, increased 2,3dpg makes it harder of oxygen to bind Hgb and more likely to be released, Increased oxygen uptake in the lungs casues 2,3 dpg to be expelled. 2,3 dpg is high when near respiring tissues, and low when in lungs.
Term
Carboxyhemoglobin
Definition
binding of carbon monoxide to the heme iron. Hgb has 200 times more affinity for CO. Hgb is incapable of transporting oxygen. .2-.8% normal, smokers as high as 4-30%
Term
Methemoglobin
Definition
when ferrous iron becomes ferric. Incapable of combining reversible with oxygen, usually aquired due to durgs or chemicals (reversible), inherited, 1.5% normal.
Term
Sulfhemoglobin
Definition
chemically modified, irreversible oxidation of Hgb by drugs and chemicals, 100 times less affinty for oxygen, rarely exceeds 10%.
Term
Normal Erythrocyte Destruction
Definition
aged red blood cells are phagocytized. Hgb is kept at normal levels, Bone marrow continues steady production. Main way RBCs die normally.
Term
Hemolysis
Definition
premature destruction of RBCs, reduced number of RBcs leads to reduced tissue oxygenation, Increased RBC production, possible anemia.
Term
Extravascular Hemolysis
Definition
90% of hemolysis, destruction outside a blood vessel, usually by macrophage, occurs in spleen, liver, marrow, lymph nodes, monocytes.
Term
Intravascular Hemolysis
Definition
10% of hemolysis, destruction of a RBC within a blood vessel.
Term
Extravascular process for recycling Heme
Definition
macrophage lyse the phagocytized erythrocyte.
Hgb hydrolyzed into heme and globin.
Globin Metabolism
Heme metabolism
Term
Globin Metabolism
Definition
globin portion of hemoglobin is broken down into amino acids which are released into the peripheral blood.
Term
Heme Metabolism
Definition
Iron released from heme, returned to plasma, once in plasma iron is bound to transferrin and carried to bone marrow where it is recycled. Protoporhyrin into biliverdin, then bilirubin, biliruin into bloodstream, picked up by liver, secreted with bile metabolized into urobilinogen, excreted.
Term
Intravascular Process of Hgb Recycling
Definition
Hgb is recycled for RBCS removed by the intravascular process, RBCs lyse in-vivo and the Hgb is released to the periphereal blood, captured by haptoglobin, carried to liver where it is phagocytized, then breakdown follows extravascular process.
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