Final answer:
Hb binds to carbamino CO₂ when it is not saturated with O2 because it is in its deoxygenated form, forming carbaminohemoglobin.
Step-by-step explanation:
Hemoglobin (Hb) binds to carbamino CO₂ when it is not saturated by O2 because it is in its deoxygenated form. This binding of CO₂ to hemoglobin is a process whereby carbon dioxide binds amino acid moieties on the globin portions of hemoglobin to form carbaminohemoglobin, particularly when hemoglobin is not transporting oxygen. The Haldane effect demonstrates this phenomenon, indicating that deoxygenated hemoglobin has a greater affinity for carbon dioxide compared to its oxygen-saturated form.