Question

1. As a molecular biologist, you have been asked to design a liposome (artificial cell). The purpose of the liposome is to carry drug to the inner linings of the stomach cells, which are cancerous. How would you design the liposome? Most specifically, what should be the biochemical properties of the cell membrane of the liposome?

2. Name and describe three functions of the cell membrane

3. explain and justify the importance of the cell membrane’s fluid mosaic model.

Answer 1

1. The cell membrane of liposome for this conditon (to transfer drug molecule) should be made up of bilayer phospholipid with as that of cell. This will provide similar environment as that of cell because the polar head part of phospholipid would be at inner side making hydrophilicity inside the liposome so that it can carry drug molecule and head part is directed outer side also so that it can also interact with its surrounding environment.

2. Functions of cell memnbrane-

a. Transportation - cel menbrane has many trans-membrane protein molecules like aquaporin which help to transport material like carbohydates, essential amino acids, water etc. to maintain haemostasis. Some of these transprotein transport ions which help to maintain the membrane potential, help in impulse transmission as in nerve cells.

b. Basic structure - cell membrane is phospholipid bilayer membrane consisting many phospolipid molecules like phosphotidylcholine, phosphotidylserine, etc. They are attached with hydrophobic interactions to form a continuoes layer. This provide cell a basic structure by which cell can survive.

c. Fluidity - cell membrane is made up phospholipid bilayer which is attached with hydrophobic interactions thus instead of providing rigid structure it has some fluidity which helps cell to move as like in some protozoans. Fluidity also help cell to perform phagocytosis by which it can engulf outer material like amoeba take its food.

3. Fluid mosiac model of cell membrane is widely accepted model, proposed by Singer and Nicolson in 1975. They described that cell membrnae is made up of phospholipid bilayer in which head of phospholipid molecule is polar in nature and its tail is of non-polar nature. the polar part is directed outside and inside both which interact with hydrophilic enviornment while the tail part which is hydrophobic in nature is remain intact in the middle associated with cholesterol moleucle which strengthen the membrane and also helps to maintain its fluidity which enable the cell to move and to perform phagocytosis. Within the membrane many protein molecules are embedded in the menbrane. Those which are facing outer side are called extransic protein while which are facing the cytosole are called intransic protein. Some protien molecules are also present as tunnel protein or as trans-membrane protein which provide path for molecules to be transported inside out the cell. Such proteins have a major in maintaining the haemostatis of the cell.Some transmenbrane protein molecules are also work as receptor molecules which help to communicate with other cells. Some glycolipid and glycoportein molecules are also attached to the outer surface of cell-membrane. It is considered that these gyco molecules help in recognising the cell.