JM

03-20-25- Biol 162

  • pH Significance

    • pH is crucial for oxygen transport in the circulatory system, alongside other factors.

    • Only about 0.7% of oxygen can be dissolved in liquid, while blood carries around 20% due to hemoglobin.

  • Role of Hemoglobin

    • Hemoglobin increases the concentration gradient of oxygen and indirectly raises the partial pressure of oxygen in the blood.

    • When oxygen binds to hemoglobin, it helps maintain a high concentration, preventing oxygen from bubbling out of solution.

    • Hemoglobin facilitates the delivery of oxygen into cells, which then use it for ATP production at the mitochondria.

  • Diffusion Process

    • The exchange of oxygen occurs due to the concentration gradient: higher concentration in blood, lower in cells.

    • As cells respire and produce CO2, this lowers pH, increasing the release of oxygen from hemoglobin.

    • Oxygen then diffuses from the blood into the cells following its partial pressure gradient.

  • Oxygen Affinity Curves: Hemoglobin vs. Myoglobin

    • Hemoglobin is a tetramer (two alpha and two beta subunits), allowing for cooperative binding of oxygen, resulting in a sigmoidal binding curve.

    • Myoglobin, a monomeric protein, has a hyperbolic binding curve, displaying a higher affinity for oxygen than hemoglobin.

    • At 50% saturation, myoglobin requires significantly less oxygen than hemoglobin to reach this saturation level, indicating its higher affinity.

  • Cooperativity in Hemoglobin

    • When one oxygen molecule binds to hemoglobin, it causes conformational changes that facilitate the subsequent binding of additional oxygen molecules.

    • This is referred to as cooperative binding, which is critical for oxygen uptake and release based on partial pressures in the lungs and tissues.

  • Physiological Factors Affecting Affinity

    • Bohr Effect: Refers to the reduction in hemoglobin's oxygen affinity in response to lower pH (higher H+ concentration).

      • Increased CO2 from tissue metabolism lowers pH, decreasing hemoglobin's affinity for oxygen and allowing more oxygen to be released.

    • Temperature Effects: Higher body temperatures reduce hemoglobin's affinity for oxygen, increasing oxygen release in active muscles where heat is generated.

    • 2,3-Bisphosphoglycerate (BPG): Produced during glycolysis, BPG binds to hemoglobin and reduces its affinity for oxygen, promoting oxygen delivery under conditions like anemia.

  • Root Effect

    • Found in some fish, manifests as a reduced capacity of hemoglobin to carry oxygen and rapid oxygen release under specific conditions, e.g., in swim bladders.

    • Enhances buoyancy by allowing fish to increase oxygen in their swim bladders as they dive deeper.

  • Comparative Analysis of Respiratory Pigments

    • Different animals have various hemoglobin affinities and carrying capacities, reflecting their ecological needs.

    • Example: Weddell seals have high oxygen carrying capacity due to adaptations for underwater survival.

  • Conclusion

    • Understanding the interplay between pH, temperature, and hemoglobin dynamics is critical for comprehending respiratory physiology and adaptations in different organisms.

    • The efficiency of oxygen transport and release mechanisms is vital for energy production and survival, especially in variable environments.