Question

How would the rate of diffusion change if the PO₂ in the capillaries was 40 mmHg and the PO₂ in the muscle cell changed from 40 to 20 mmHg?

• The rate of diffusion would increase.

• The rate of diffusion would decrease.

• The rate of diffusion would approach zero.

• The rate of diffusion would remain the same

Answer 1

Answer is option (a) The rate of diffusion would increase.

Transfer of O2 from blood to body tissue is occurring by the mechanism of simple diffusion.

It happens along the pressure gradient. i.e, from the region of higher partial pressure to the region of lower partial pressure of oxygen.

If pO2 changes from 40 to 20 in the muscle cells, and pO2 in the blood is 40 mmHg, pressure gradient increases. This causes increase in diffusion rate of oxygen from blood to muscle cells.

**According to Fick's law, factors affecting the diffusion of gases through fluid are:

• partial pressure difference
• solubility of gas.
• distance molecules need to diffuse.
• cross-sectional area of the fluid.
• molecular weight of gas.