Question

Which of the following factors raise the $P _{50}$ value and shifts the $HbO _{2}$ dissociation curve to right and vice versa ?
(1) Rise in $PCO _{2}$
(2) Rise in $H ^{+}$ions (= fall in $pH$ )
(3) Fall in temperature
(4) Fall in diphosphoglyceric acid

• A. 1, 2 and 3 are correct
• B. 1 and 2 are correct
• C. 2 and 4 are correct
• D. 1 and 3 are correct

Answer 1

Answer: (B)

A rise in body temperature, concentration of $2,3$ diphosphoglycerate (DPG) in $RBCs$ or $P _{ CO _{2}}$, or a fall in blood $pH$ (increase $\left.H ^{+}\right)$, decreases $O _{2}$-affinity of haemoglobin revising $P_{50}$ and shifting the $O _{2}$-haemoglobin dissociation curve to the right.