The quaternary structure of hemoglobin changes from the T state to the R state ________.
A)only after four molecules of O² are bound
B)after the binding of one molecule of O² causes a change in the primary structure
C)when hemoglobin is completely deoxygenated
D)when at least one subunit on each dimeric unit (αβ dimer)is oxygenated

Question

Quizplus · Accepted Answer

The quaternary structure of hemoglobin changes from the T state to the R state when at least one subunit on each dimeric unit (αβ dimer)is oxygenated. This triggers a conformational change that leads to the remaining subunits also adopting the R state, resulting in increased oxygen affinity. This phenomenon is known as cooperativity. Option A is incorrect as all four oxygen-binding sites do not need to be occupied for the switch from T to R state. Option B is incorrect as a change in primary structure would result in a different protein altogether. Option C is incorrect as complete deoxygenation would result in the T state.

The Quaternary Structure of Hemoglobin Changes from the T State