The Cell and Cell Differentiation PDF

## THE CELL AND CELL DIFFERENTIATION - The Cell: - Cell is the fundamental unit of a living organism (plants and animals). - The Cell consists of Cell wall and nucleus appears to be suspended within cell by cytoplasm in which there may be large vacuoles with their own characteristic content...

## THE CELL AND CELL DIFFERENTIATION - The Cell: - Cell is the fundamental unit of a living organism (plants and animals). - The Cell consists of Cell wall and nucleus appears to be suspended within cell by cytoplasm in which there may be large vacuoles with their own characteristic contents (crystals and aleurone grains). - Other cytoplasmic inclusions are mitochondria, Golgi bodies, lysosomes, and plastids. - A group of cells with identical form and function is known as a tissue. ## Plant cell - An image of a plant cell is shown, with the following parts labelled: - Golgi Complex - Endoplasmic Reticulum - Mitochondria - Nucleus - Nucleolus - Cell Wall - Vacuole - Membrane - Peroxisome - Cytoplasm - Chloroplast ## The Cell Wall: - The wall of mature Cell consists of: - The middle lamella is the intercellular substance, an amorphous, colloidal layer composed of pectic substance. - Primary wall or the original cambial wall is composed of cellulose and pectic substance. - Secondary wall is formed after the enlargement of the cell has been ceased. It consists mainly of cellulose associated with polysaccharides. - It undergoes to some modifications as desposition of various chemical substance as lignin, suberin and cutin. - Tertiary wall: It is the innermost layer of the cell wall and is usually thin, highly refractive and formed of cellulose. ## Properties of different cell walls: ### A. Cellulosic Walls: - Formed mainly of cellulose which may be accompanied with hemicellulose and pectin. - Cellulose is polysaccharide, composed of linear chain of glucose residue. - Chemical Properties: - Give blue color with iodine and sulphuric acid. - Give blue color with chloro- Zinc- iodine. - Give no color with aniline or phloroglucin and HCL. - They dissolve in ammonical solution of copper oxide (Cuoxam) and precipitated with dilute sulphuric acid. ### B. Mucilaginous Walls: - Certain cellulosic cell walls may be converted into gums and mucilages. - Mucilage is polysaccharides, consisting of sugar and uronic acid combined with metals. - Chemical Properties: - They are variably stained with ruthenium red, iodine sulphuric acid or corallin soda. ### C. Lignified Walls: - Lignin is a strengthening material. - Chemically it is a complex phenylpropaniod polymer. - Chemical Properties: - Stain magenta red with phloroglucin and hydrochloric acid. ### D. Suberised and cutinized walls: - Suberin and cutin are mixture of polymerized fatty acids and suberic acid. - Chemical Properties: - Stain red with alkanna tincture and sudan II ### E. Chitinous walls: - Chitin is a polysaccharide derivative containing acetyl and amino group. - It constitutes the organic skeletal substance of insects and many fungi. - When heated with 50% potash at 160 – 170 o C for 1 hour, it is converted into chitosan C14H26016N2, ammonia and acids such as acetic and oxalic. - Chitosan gives a deep violet coloration when treated with iodine solution followed by dilute sulphuric acid.