Question

At high altitude, the partial pressure of oxygen is less than that at the ground level. This leads to:
(A) the low concentration of oxygen in the blood and tissues.
(B) the high concentration of oxygen in the blood and tissues.
(C) release of dissolved gases and formation of bubbles of nitrogen in the blood.
(D) thickening of blood and tissues.

Answer 1

The pressure of the substance is related to its weight over a unit area. The pressure decreases with height. Also, this pressure is closely related to the concentration of the substance.

Complete step by step solution:
The atmospheric pressure is the pressure exerted by the air around us, which is determined by the force exerted by the air molecules over a unit area. This force is further dependent on the weight of the air.
It consists of partial pressure due to its constituent gas particles like oxygen, nitrogen and also water vapour. This makes the atmospheric pressure highest above the sea level due to the air being dense.
But this decreases with the elevation in height because at higher altitudes the gas molecules are further apart. So, the weight of the air decreases, that is, the decrease in the force exerted by the air molecules over a unit area decreases. Thus, the atmospheric pressure falls linearly with increasing altitude.
$Pressure=\dfrac{force}{area}=\dfrac{m\times g}{a}=\dfrac{(V\times \rho )\times g}{a}=\rho gh$
Therefore, $P\,\propto \,h$
where, $m$ is the mass, $a$ is area, $g$ is acceleration, $V$ is volume, $\rho$ is density and $h$ is height.
Then, this atmospheric pressure around us is related to the partial pressure of inspired oxygen. As it allows the oxygen to be inhaled into the lungs and through its selectively permeable membrane it gets dissolved into the blood.
The partial pressure of oxygen (P) is directly proportional to the concentration of the dissolved oxygen (C). As seen in the formula: $\,PV=nRT\,\,or\,P=CRT$.

Therefore, at high altitude, the partial pressure of oxygen is less than that at the ground level. This leads to option (A)- low concentration of oxygen in the blood and tissues.

Note: At the higher altitudes, due to the lower partial pressure of oxygen, which reduces the driving pressure for the exchange of gas in the lungs. The amount of oxygen getting dissolved into the blood is low. This results in oxygen deprivation or hypoxia.