In hemoglobin, the transition from T state to R state (low to high affinity) is triggered by Select one: a. Oxygen binding. b. Subunit disassociation. c. Iron binding. d. Subunit association.

a. Oxygen binding

Explanation:

the two energetic states are the tense (T) and the relaxed (R) states. The two states differ from each other in their affinity for ligand and in the interactions between subunits. Binding of oxygen to the deoxygenated (deoxy) - T state occurs with low affinity. However, the binding of the ligand destabilizes the T state and makes it more likely to switch to the high-affinity oxygenated (oxy) - R state. Thus, as ligation proceeds, the gradual enrichment in Hb molecules in the R state accounts for cooperativity in ligand binding.