What does $Methemoglobin$ indicate?

What is true about $RBCs$ in humans?

What should be the nature of blood for the efficient transport of $O_2$ and $CO_2$?

What is the amount of oxygen carried by $1 \, g$ of hemoglobin?

How is $CO_2$ transported from tissues to the respiratory surface?

What are $P$ and $Q$ in the given reaction?
$CO _2+ H _2 O \underset{Q}{\stackrel{P}{\rightleftharpoons}} H _2 CO _3 \underset{Q}{\stackrel{P}{\rightleftharpoons}} HCO _3^{-}+ H ^{+}$