Chapter 24: Transport of Oxygen and Carbon Dioxide in Body Fluids

The authors provide an in-depth explanation of respiratory pigments, with hemoglobin as the primary focus in vertebrates. Key concepts such as oxygen-binding affinity, cooperativity, and the oxygen equilibrium curve (OEC) are explored. The chapter explains how hemoglobin's sigmoidal binding curve allows it to load oxygen efficiently in the lungs and unload it in tissues, and introduces the Bohr effect—whereby lower pH or higher CO₂ decreases hemoglobin’s oxygen affinity to enhance oxygen release in metabolically active tissues. Other pigments like myoglobin (with higher O₂ affinity) and hemocyanin (found in arthropods and mollusks) are also discussed. Carbon dioxide transport is explained in its three primary forms: dissolved CO₂, bicarbonate (HCO₃⁻), and carbamino compounds. The chapter introduces carbonic anhydrase as a key enzyme that catalyzes the conversion of CO₂ to bicarbonate in red blood cells. The chloride shift (exchange of Cl⁻ for HCO₃⁻) is described as critical for maintaining electrochemical balance during gas exchange. The Haldane effect—where deoxygenated blood binds more CO₂—is also highlighted as a complement to the Bohr effect, enhancing total CO₂ transport. The chapter concludes by showing how all these processes integrate into the oxygen cascade from atmosphere to mitochondria, and the carbon dioxide removal pathway from tissues to environment. Emphasis is placed on how gas transport systems are finely tuned to meet the metabolic demands of different animals under varying environmental and activity conditions. This chapter bridges respiratory mechanics and cellular metabolism by detailing how blood chemistry dynamically supports homeostasis and performance.