Chapter 8, Problem 11STP

Solution

To compare:

The structure of cell membrane and cell wall.

Introduction:

Cells are the basic structural and functional unit of life. They are the building blocks of all living things. They provide structure for the body, take in nutrients from food, transform those nutrients into energy, and carry out specific functions. Cells have many constituents, each with a different function. Some of these parts, called organelles, are specified structures that carry out certain functions within the cell.

Cell wall was first discovered by Robert Hooke.

Cell wall is the outermost covering of the cell and it provides protection. Cell wall is present in plant cell, bacteria and fungi while it is absent in animal cell.

Chemical composition of cell wall is different in different living organism such as fungal cell wall is made up of chitin, algal cell wall is made up to cellulose, galctans, mannans, and crystals of some minerals.

Plant cell wall is made up of cellulose, pectin and protein. Cell wall is made up of three components namely, primary wall, secondary wall and middle lamella.

Primary wall is single layered and developed through process of intussception. Secondary cell wall develops toward inner side of primary wall and develops through the process of apposition. It develops during maturation of cell.

Middle lamella acts as connecting layer and connects primary and secondary wall.

Cell membrane is outermost layer of cell after cell wall and is composed of lipid bilayer. These lipids are arranged within the membrane with polar heads towards the outer sides and hydrophobic towards inner sides. The polar end interacts with water and is called hydrophilic and non-polar tails are protected from aqueous medium.

Cell membrane also possesses protein and carbohydrate and the ratio of lipid and protein varied in different cell types.

The structure of cell membrane is similar in all eukaryotes.