Question

Describe e Biological membranes present as barrier to polar molecules and enumerate the system of transport proteins across the membranes

Answer 1

The plasma membrane defines the cell as an individual entity. It is a lipid bilayer which is a continuous barrier that prevents the free passage of water-soluble (or polar) substances such as nutrients, ions and other substances. Several proteins contained in the lipid bilayer or located on one of its surfaces carry out most of the functions of the membrane. For example some proteins are channels and other distribution pumps through the bilayer. Others are receptors for hormones or signaling molecules that trigger changes required in cellular activities.