Question

How can water pass through lipid bilayer?

Answer 1

Hint: Lipids or fats are hydrophobic, which means they cannot interact with water due to which lipid layers are impermeable to water.

Complete answer:
Although the lipid bilayer does not allow movement of water through it, some amount of water can pass through the lipid bilayer because of the small size of the water molecule, but this method cannot be used for water transportation across the lipid bilayer because diffusion can be only used to transport a very small amount of water.

 Another method that is used for transportation of water across lipid bilayer is osmosis, as the lipid bilayers are mainly present on the outer side of the cell and the osmotic pressure outside the cell and the osmotic pressure inside the cell shows a large difference and osmosis can be used to transport water across lipid bilayers but the process of osmosis is slow. Another method of water transportation of lipid bilayer which is widely used is through the aquaporins, which are specific proteins present in the lipid bilayer and the main function of aquaporins are to transport water across the lipid bilayer.

Note: Aquaporins are also known as water channels or protein channels. The aquaporins were discovered by Peter Agre for which he received the Nobel prize in 2003 with another scientist Roderick Mackinnon for the discovery of potassium channels. Abnormalities in aquaporins can cause several diseases such as diabetes insipidus and other disorders related to nerves, spinal cord, etc.