Question

"A selectively permeable membrane is essential for life”. Critically discuss this statement using a range of relevant examples of your choice.

Answer 1

Selective permeability of a membrane indicates its ability to allow some molecules to enter the cells and prevent the entry of unwanted molecules. As cell is the basic unit of life, it is the selective permeability of the cell membrane that enable the cell to maintain its structure and function. Thus existance of life is basically due to the property of semi permeablity of a cell membrane which maintain osmotic balance and constant internal environment or homeostasis.

As far as a cells in body is concerned , they are exposed to varrying internal environment with respect to concentration of water molecules or ions. The selective permeability allows controlled movement of molecules according to the need of the cell.

Most of the life process are achieved by this property of semipermemblity of cell  membrane. Examples are given

During cellular respiration in mitochondria selective permeability allows selective import of molecules which is unaffected by other metabolic process inside cytoplasm.

Nerve impulse transmission through neurons through generating electrochemical gradient across cell membrane is also achieved by the property of seletive permeability of nerve cell membrane.

Electochemical properties of cardiac cells which allows uninterrupted heart beating is due to the selective permeability of heart cell membrane.

As a whole, the integrity of each and every cell organ is provided by the selective permeability of cell membrane. The unique environment in each end every tissue/ cell is thus achieved to perform all the cellular functions which facilitate the existance of an organism.