Question

What do you mean by the permeability of the membrane? Explain with a suitable example?

Answer 1

Hint: The permeability of a membrane refers to the property of the membrane by which it allows the only selective substance to pass through it. The selection is based on several factors including size, charge, solubility, and saturation. The cell wall is the easiest example to understand the permeable membrane. It allows transport of all types of water, free ions, and substances that are soluble in water.

Complete answer:The permeability of a membrane refers to the rate of passive diffusion of molecules through the membrane. These molecules are identified as permeant molecules. Permeability relies mainly on the electric charge and polarity of the molecule and to a secondary extent on the molar mass and size of the molecule. Passive transport refers to the movement of molecules across the cell membrane and does not require energy. It relies upon the permeability of the cell membrane. There are three fundamental kinds of passive transport - Diffusion, Osmosis, and Facilitated Diffusion.
Simple diffusion – transfer of small or lipophilic molecules (e.g. oxygen, etc.)
Osmosis – transport of water molecules (dependent on solute concentrations)
Facilitated diffusion – transport of large or charged molecules via membrane proteins (e.g. ions, sucrose, etc.).
The most common example of the permeable membrane is the phospholipid bilayer cell membrane. It surrounds every cell in our bodies. Phospholipids are molecules composed of a hydrophilic, or water-loving, head, and a hydrophobic, or water-fearing, tail. A cloth through which liquids can pass right is an example of permeability. Rainwater sinks through the permeable rock to form an underground reservoir is another example.

Note: The cell membrane also referred to as the plasma membrane, is a double layer of lipids and proteins. It surrounds a cell and separates the cytoplasm (the contents of the cell) from the external environment. It is a characteristic of all cells, both prokaryotic and eukaryotic.