HEMOGLOBIN

HEMOGLOBIN

Structure
1. 4 Globin
  1. Polypeptide chains
    1. A and B
2. 4 Heme groups that bind O2
3. 4 O2/Hb
Hemoglobin and O2 Transport
1. Iron
  1. Containing protein found in RBC transports respiratory gases
2. Loading (Hb bindding to O2) occurs in lungs
  1. Unloading occurs in tissues
3. Affinity of Hb for O2 changes with a number of physiological variables
  1. Temperature altitude pH
4. Most 02 in blood is bond to Hb inside RBC as OXYHEMOGLOBIN
5. Hb increases the O2 carrying capacity of blood
Carbon Monoxide & O2 Transport
1. Carboxyhemoglobin
  1. Heme combined with CARBON MONOXIDE
2. Bond with CO is 250 times stronger than bond with O
  1. so heme cannot bind 02
    1. Thus interferes with Oxygen carrying capacity of blood
Hemoglobin & O2 transports
1. O2 Carrying capacity of blood also depends on Hb Levels
  1. ANEMIA
    1. Hb levels are below normal
    2. Reduction of RBC
    3. physiological adaptations include:
      1. each RBC produces more DPG
2. Hb production normally controlled by Erythropoietin
  1. Stimulated by low PO2
3. High PO2 of lungs favors loading
4. Low PO2 in tissues favors unloading
5. Hb 02 affinity should allow maximum loading in lungs & unloading in tissues
Oxyhemoglobin Dissociation Curve
1. Hb-oxygen binding depends on oxygen pressure (amount)
2. 98% Saturation at 100mmHg oxygen (arteries )
3. 75% Saturation at 40mmHg at 40mmHg oxygen (veins)
4. 60 mmHg unloaded at tissues
Bohr Effect
1. Hb-Oxygen affinity decreases due to pH, increase CO2 and Increase temperature
  1. Occurs in metabocally active tissues
    1. caused Hb-O2 curve to shift right (more unloading
      1. Oxygen INCREASES at lungs DECREASES Hb-CO2 affinity (Haldane Effect)
Effect of hypoxia on O2 transport
1. Hypoxia LOW OXYGEN
  1. Less oxygemoglobin
    1. less tissue transport
      1. 2,3 DPG gycolysis by product RBC no mitochondria
        Binds to Hb
        Adaptations to hypoxia:
        DECREASE DPG INCREASES HB OXYGEN AFFINITY
        INCREASE DPG DECREASES OXYGEN AFFINITY AND FACILITATES DELIVERY TO TISSUES
2. Fetal Hemoglobin
  1. Cant bind DPG
  2. Have higher O2 affinity thus facilitates mother fetus oxygen delivery
Pathologies
1. SICKLE-CELL ANEMIA
  1. Affects 8-11% African A.
    1. Valine substituted fro glutamic acid on B chains
  2. Formation of hemoglobin S
  3. RBC become fragile, rigid sticky and clump together
  4. Impaired O delivery to organs
  5. Reactivation of HbG HYDROXYUREA AS A TREATMENT
2. Thalassemia
  1. Mostly affects people of Asian Mediterranean origin
    1. Failure in production of either B or A chains
      1. Small RBCs
        Anemia
        Imapired Oxygen delivery to organs
CABON DIOXIDE TRANSPORT
1. CO2 transported in blood as:
  1. dissolved CO2 in plasma 10%
    1. Bicarbonate ion HCO3- 70%
      1. Carbaminohemoglobin 20%
2. Carbonic anhyfrase catalyzes formation of H2CO3
  1. Carbonic acis from CO2 + H2O Dissociates into H+ and HCO3-
3. ACIDOSIS
  1. pH lower than 7.35
    1. Respiratory acidosis caused
      1. Hypoventilation
      2. Causes rise in blood CO2 & carbonic acid
  2. Metabolic Acidosis
    1. Result form excess nonvolatile acids
      1. fat breakdown in diabetes or loss of HCO3- in diarrhea
4. Alkalosis
  1. pH greater 7.45
  2. Respiratory alkalosis
    1. hyperventilation
      1. too little CO2
        Response to high altitude low Oxygen to correct the pH balance
  3. Metabolic Alkalosis
    1. caused by too much HCO3- or too little acids
      1. from vomiting out stomach acid

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	Created by Susy Sanchez about 11 years ago