STRUCTURE OF EUKARYOTIC CELL
A cellingeneral comprises of following main compcomponentsal.
- Cell wall It is the outer rigid, protective a semitransparent covering of plant cells, fungi and some protists. The cell wall of algae have alginic acid while cell wall of fungi have glucosamine and chitin. The plant cell wall is composed of a variety of polysaccharides, lipids, proteins and mineral deposits like silicates and carbonates of calcium and magnmagnesic. function= Provides shape and rigidity to cell Protects protoplasm from mechanical injury. Counteracts osmotic pressure and prevents bursting of plant cells by inhibiting excessive endosmosis.
- Cell Membrane Cell or plasma membrane bounds the cytoplasm on the outerside and also covers the cell organelles inside the cytoplasm. Various models have been put forth to explain the structure of biomembrane but the most widely accepted one is fluid mosaic model. Fluid mosaic model - It was proposed by Singer and Nicolson in 1972. Fluid mosaic model describes cell membrane as 'protein icebergs in a sea of lipids'. According to this model, there is a bilayer of lipid molecules (phospholipid) with globular protein molecules (2 types- integral and peripheral) and sterols which are arranged in different manner in different regions of the plasma membrane. Integral or transmembrane proteins go through the membrane. They have hydrophobic regions within the interior of the membrane and hydrophilic regions at the outer membrane surface. - Peripheral proteins are attached to the surface of the membrane, often to the exterior hydrophilic regions of the transmembrane proteins. . Function = Cell membranes cause compartmentalisation and allow organelles to maintain identity and internal environment. Protects cell from injury and allows flow of materials and information between different organelles as well as cells. Selective permeability of plasma membrane enables them to selectively allow some substances inwardly It possess carrier proteins for facilitated and active transport.
