In hemoglobin, the high-affinity state in the lungs is referred to as the ____________ state.

In hemoglobin, the high-affinity state in the lungs is referred to as the relaxed (R) state. This state is characterized by a higher affinity for oxygen, which facilitates the binding of oxygen molecules to the heme groups in hemoglobin. In the lungs, where the concentration of oxygen is high, hemoglobin transitions into this R state, allowing for efficient loading of oxygen.

The R state allows for a conformational change in hemoglobin that increases the protein’s affinity for additional oxygen molecules. This sequential binding of oxygen enhances the overall oxygen-carrying capacity of the hemoglobin molecule. As hemoglobin binds oxygen, it undergoes a shift from the tense (T) state, which has a lower affinity for oxygen, to the R state.

Understanding the difference between the T and R states is crucial for comprehending how hemoglobin functions in various physiological environments, such as the lungs and tissues, where oxygen needs fluctuate.