Answer to Question #132426 in Chemistry for Vandana gupta

Question

Describe different modes through which cell membrane controls the transport of ingoing and outgoing molecules

Answer 1

The living cell has several possible mechanisms that provide fine control of membrane transport. Some molecules pass the membrane via simple diffusion due to the concentration gradient. This transport is specific for hydrophobic molecules that can simply penetrate the membrane. Other types of molecules require specific membrane proteins and are transported via facilitated diffusion. This process occurs due to the presence of specific channels or transporters - transmembrane proteins that provide the transportation of the substances through the membrane. Simple and facilitated diffusion are types of passive transport. Other molecules are transported through the membrane against their concentration gradient. This type of transport is energy-dependent and is called active transport. It is provided by specific transmembrane proteins, channels or pumps, that hydrolyze ATP. Finally, membrane uses endocytosis and exocytosis, forms of active transport, for the transportation of large molecules via membrane fusion or fission.