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Hemoglobin Cooperativity definitions

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  • Hemoglobin
    Protein with four subunits, displays positive cooperativity and sigmoidal oxygen binding, optimizing oxygen delivery to tissues.
  • Myoglobin
    Single-subunit protein with hyperbolic oxygen binding, high affinity, poor oxygen release to tissues, lacks cooperativity.
  • Positive Cooperativity
    Phenomenon where binding of one ligand increases affinity for additional ligand binding in multi-subunit proteins.
  • Sigmoidal Curve
    S-shaped plot representing hemoglobin's oxygen binding, indicating cooperative ligand binding behavior.
  • Hyperbolic Curve
    Rectangular plot seen in myoglobin's oxygen binding, reflecting non-cooperative ligand binding.
  • T State
    Conformation of hemoglobin with low oxygen affinity, prevalent at low partial pressures, termed tense state.
  • R State
    Conformation of hemoglobin with high oxygen affinity, prevalent at high partial pressures, termed relaxed state.
  • Allosteric Protein
    Protein whose function is regulated by conformational changes induced by ligand binding at specific sites.
  • Concerted Model
    Theory where all subunits of a protein transition between states simultaneously, explaining cooperative binding.
  • Sequential Model
    Theory where subunits change conformation individually, with neighboring subunits gaining increased affinity.
  • Partial Pressure of Oxygen
    Measurement of oxygen concentration in gases, directly proportional to hemoglobin's oxygen affinity.
  • Fractional Saturation
    Ratio indicating proportion of protein binding sites occupied by ligand, plotted on oxygen binding curves.
  • Threshold Effect
    Ability of hemoglobin to release more oxygen to tissues with lower oxygen levels, optimizing delivery.
  • Homotrophic Allosteric Activator
    Ligand that enhances its own binding to a protein, as oxygen does for hemoglobin.
  • BPG
    Heterotrophic allosteric effector that increases hemoglobin's oxygen release to tissues, enhancing transport efficiency.