Final answer:
Hemoglobin carries O2 better when it is in the relaxed form (R state) since it has a higher affinity for binding oxygen, as opposed to the taut form (T state), which has a lower oxygen affinity. The correct option is a.
Step-by-step explanation:
Hemoglobin is a metalloprotein found in red blood cells that is crucial for oxygen transport in the body. The molecule undergoes a conformational change as it binds oxygen, each hemoglobin molecule being able to carry up to four oxygen molecules.
This binding process is easier for the second and third oxygen molecules than for the first due to a change in the shape or conformation of the hemoglobin molecule. The fourth oxygen binds with more difficulty. The hemoglobin molecule exists in two forms: the relaxed (R) state and the taut (T) state.
The relaxed form is associated with a higher affinity for oxygen and is therefore better at binding oxygen. In contrast, the taut form has a lower affinity for oxygen. The transition from the T state to the R state facilitates the binding of additional oxygen molecules, making the R state (relaxed form) better for carrying oxygen.
As more oxygen binds, hemoglobin shifts more towards the relaxed state, allowing for easier binding of oxygen, which is demonstrated in the sigmoidal shape of the oxygen dissociation curve. Ultimately, the relaxed form of hemoglobin is more efficient at oxygen transport from the lungs to the tissues of the body. The correct option is a.