1. Hemoglobin is a protein composed of heme and globin subunits. It transports oxygen and carbon dioxide in the blood. 2. Hemoglobin exists in two forms - oxygenated (R form) and deoxygenated (T form). Allosteric effectors like 2,3-DPG stabilize the T form, lowering hemoglobin's affinity for oxygen and allowing release in tissues. 3. Carbon dioxide and protons also decrease hemoglobin's oxygen affinity through allosteric effects, facilitating oxygen delivery and carbon dioxide transport between lungs and tissues.