The degree in which materials are able to flow freely through a cell's membrane is known as

The degree in which materials are able to flow freely through a cell's membrane known as permeability.

Explanation:

The permeability of membrane is the rate of passive transport through the membrane. These molecules are known as permeant molecules.The permeability of a cell membrane  are dependent on certain factors such as  polarity, electric charge and molar mass of the molecules which diffuse through the cell membrane. Phenylalanine increases the permeability of membrane. When there is an increase in the temperature it also increases the  permeability of membrane. When there is a water in the cells it will result in water expansion, there will be exertion of pressure on membrane and deformation of the transport proteins so that they will able to control what will enter or leave the cell. Selective permeability of the membrane plays a very significant role in maintaining homeostasis, fluid & electrolyte balance & cellular health.

b.have there own function.