The Cell and Cell Differentiation PDF

# The Cell and Cell Differentiation - **The Cell:** - The fundamental unit of a living organism (plants and animals). - Consists of a cell wall and nucleus, which appears to be suspended within the cell by cytoplasm. - May contain large vacuoles with characteristic contents such as cr...

# The Cell and Cell Differentiation - **The Cell:** - The fundamental unit of a living organism (plants and animals). - Consists of a cell wall and nucleus, which appears to be suspended within the cell by cytoplasm. - May contain large vacuoles with characteristic contents such as crystals and aleurone grains. - Other cytoplasmic inclusions include mitochondria, Golgi bodies, lysosomes, and plastids. - A group of cells with identical form and function is known as a tissue. ## Plant Cell The following are parts of a plant cell: - Cell Wall - Vacuole - Membrane - Peroxisome - Mitochondria - Cytoplasm - Nucleus - Nucleolus - Chloroplast # The Cell Wall - The wall of a mature cell consists of: - **Middle lamella:** This is the intercellular substance, an amorphous, colloidal layer composed of pectic substance. - **Primary wall:** The original cambial wall composed of cellulose and pectic substance. - **Secondary wall:** Formed after the enlargement of the cell has been ceased. It consists mainly of cellulose, associated with polysaccharides. - **Tertiary wall:** This 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 by hemicellulose and pectin. - Cellulose is a polysaccharide, composed of a linear chain of glucose residue. ### Chemical Properties: - Give blue color with iodine and sulfuric 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 precipitate with dilute sulfuric acid. ## B. Mucilaginous Walls - Certain cellulosic cell walls may be converted into gums and mucilages. - Mucilage is a polysaccharide consisting of sugar and uronic acid combined with metals. ### Chemical Properties: - They are variably stained with ruthenium red, iodine sulfuric 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 mixtures of polymerized fatty acids and suberic acid. ### Chemical Properties: - Stain red with alkanna tincture and Sudan III. ## E. Chitinous Walls - Chitin is a polysaccharide derivative containing acetyl and amino groups. - It constitutes the organic skeletal substance of insects and many fungi. ### Chemical Properties: - When heated with 50% potash at 160 - 170 ⁰C 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 sulfuric acid. # Cell Differentiation - Plant Tissue may be: - **Parenchymatous Tissues:** This is the fundamental or ground tissue of the plant. They are cellulosic, isodiametric or slightly axially elongated cells with narrow or wide intercellular spaces. The cells show different contents such as starch granules, calcium oxalate crystals, etc. They constitute most of the pith and cortex of the plant. - **Collenchymatous Tissues:** This is a living mechanical tissue, composed of rounded or elongated cells with unevenly thickened, nonlignified walls. The thickening is of cellulose and is located commonly in the angles (angular collenchyma), or chiefly on the tangential walls (lamellar collenchyma). Collenchyma constitutes the typical mechanical tissue of the herbaceous stems, and of the petioles and midribs of leaves.