Question

A large proportion of oxygen is left unused in the human blood even after its uptake by the body tissues. This $O_{2}$

• A. Raises the $pCO_{2}$ of blood to $75mm$ of $Hg$ .
• B. Is enough to keep oxyhaemoglobin.
• C. Helps in releasing more $O_{2}$ to the epithelial tissues.
• D. Acts as a reserve during muscular exercises.

Answer 1

Answer: (D)

Our tissues are able to utilise only $25\%$ of $O_{2}$ carried by arterial blood. The venous blood is still $75\%$ saturated with $O_{2}$ . This $O_{2}$ acts as a reserve during muscular exercise.