Which of the following concerning hemoglobin is true? a) BPG decreases at high altitudes and causes more O2 offloading in tissues b) As pH increases, [CO2] increases in tissues, causing more O2 release in tissue c) The R state is stabilized by CO2 binding, whereas the T state is stabilized by O2 binding d) About 38% of oxygen dissociates from hemoglobin in tissues e) Hemoglobin has a higher affinity for oxygen than carbon monoxide My guess is D.

Hemoglobin (Hb) is a tetrameric protein. One molecule of Hemoglobin can bind to four oxygen molecules. The binding and release of oxygen from the hemoglobin depends on many factors such as concentration of carbon dioxide, pH, concentration of oxygen and 2,3-BPG, a factor produced by RBCs itself. Hemoglobin molecule occurs in two state-R (relaxed) and T (tensed) and the transition from R to T or T to R is the basis for binding and release of oxygen.

The enzyme carbonic anhydrase is responsible for maintaining the equilibrium between CO₂ and H⁺ in blood. The reaction catalyzed by the enzyme is given below.

$C{O}_2 + H_{2}O \rightleftharpoons H^{+} + HC{O_3}^{-} ----\left(reaction1\right)$