gas transport/ antigens and antibodies

  1. what is the relaxed state of hgb
    • "oxyhemoglobin"
    • has a higher affinity for oxygen than T form, whether or not oxygen in present
    • a dipeptide rotates opening a 15 degree cleft
  2. what is a tense state
    • "dexoxyhemoglobin"
    • stabilized by salt bridges between chains. when oxygen binds, Hgb transforms to R-form and salt bridges are disrupted
  3. describe the process of cooperativity in Hgb
    • bound O2 pull iron atom into the plane of the heme
    • movement of the iron pulls the proximal his
    • movement of his disrupts salt bridges and frees up subunit, transforming into R-state
    • binding of O2 to second subunit triggers same sequence, enhancing binding to third subunit
  4. what effect does proton, CO2, and 2-3 BPG all affect Hb
    • incrs affinity for O2 in lung
    • decrs affinity for O2 in tissues
    • all cause O2 affinity curve to R-shift
    • all induce relaxed to tense transition through salt bridge formation
  5. what is the bohr (proton) effect
    • when O2 binds to Hgb it makes Hgb sensitive to physiological pH changes.
    • contracting muscle: lactic acid is produced causing [H+] to increase, which promotes O2 dissociation
    • H+ antagonizes the binding of O2 to Hgb
    • in lungs higher pH increases affinity of Hg for O2
  6. describe how the Bohr effect is in terms of R and T
    • H+ induces R to T conversion
    • His becomes protonated giving it a (+) charge.
    • induces salt bridge formation with Asp a characteristic of T state
  7. describe the role of CO2 in hemoglobin
    • CO2 is byproduct of metabolism. Accumulation of CO2 is a result of active metabolism and increased O2 requirements by the tissue
    • CO2 lowers the affinity of Hb for O2, so that in the tissues O2 is released. 
    • in the lungs CO2 is kept lower by expiration, increasing affinity of Hgb for O2
  8. describe carbon dioxide in terms of R and T
    CO2 binds to the N terminus of Hgb and forms a salt bridge, stabilizing the T state
  9. describe the role of 2,3 BPG
    • 2,3 BPG is produced in the RBC from the metabolism of glucose
    • BPG lowers the affinity of Hgb for O2
    • accumulation of BPG is a characteristic of active metabolism and increased O2 requirements by the tissue
    • in the lungs, when O2 is bound the caivty where BPG binds becomes small, thus increasing affinity for O2 in lungs
  10. describe the role of 2,3-BPG in terms of R and T
    the neg BPG interacts with + charged residues (Lys, His) crosslinking the B-subunits. This stabilized the T state
  11. What are the protein subunits of fetal hemoglobin
    gamma and alpha
  12. describe how fetal Hgb has a higher affinity for O2 than adult Hgb
    • gamma subunit has more Ser than His, this decreases salt bridge formation
    • results to more relaxed state.
  13. what are isoforms and give and example
    • isoforms: distinct forms of a protein that have the same function but are found in different tissues
    • fetal Hgb and adult Hgb
Card Set
gas transport/ antigens and antibodies
tense and relaxed form of hemoglobin. structure of antibodies