Saran's Learn Microbiology

  RIBOSOMES —   Bacterial cells have thousands of Ribosomes in their cytoplasm, which gives cytoplasm a grainy appearance. —   Number of Ribosomes in bacterial cell varies from 10000 to 15000. —   Chemically, a Ribosome is a combination of a special type of RNA called ribosomal RNA, or rRNA (about 60 %), and protein (40 %). —   Ribosomes are the sites of Protein synthesis (Translation) in cells. —   The Ribosomes are held together by mRNA and form Polyribosomes or Polysomes.   —   All Ribosomes are composed of two sub-units, each of which is composed of polypeptides and molecules of RNA called ribosomal RNA (rRNA). The sub-units of Prokaryotic 70S ribosomes are a smaller 30S sub-unit and a larger 50S sub-unit. ü   The 30S sub-unit contains Polypeptides and a single rRNA molecule ü   The 50S sub-unit has Polypeptides and two rRNA molecules. —   The letter S refers to Svedberg units, which indicate the relative rate of sedimentation during ultra-high-speed centrifugatio

  CELL INCLUSIONS —       Within the cytoplasm of prokaryotic cells, several kinds of reserve deposits, known as Inclusions or Cell Inclusions or Inclusion bodies. ·    Cells may accumulate certain nutrients when they are plentiful and use them when the environment is deficient. ·        Some inclusions arc common to a wide variety of bacteria, whereas others are limited to a small number of species and therefore serve as a basis for identification. TYPES OF CELL INCLUSIONS a)      Metachromatic Granules b)      Polysaccharide Granules c)      Lipid Inclusions d)      Sulfur Granules e)      Carboxysomes a) Metachromatic granules ·    Metachromatic granules are large inclusions that take their name from the fact that they sometimes stain red with certain blue dyes such as Methylene blue (Metachromasia). ·     Metachromatic Granules are made up of Polymetaphosphates and also called as Volutins or Volutin Granules or Babe Ernst Granules or Polar Bodies. ·     Vo

  PLASMA MEMBRANE —   Plasma membrane is also called as Cytoplasmic Membrane or Cell Membrane. —   It act as a boundary of the bacterial cell. —   Plasma membrane is found in the bacterial cells that separates the interior of the cell from the outside environment. —   Plasma membrane measures about 5 to 10 nm thick. —   In Prokaryotes, the Plasma membrane is made up of Phospholipids (20 % to 30 %) and Proteins (60 % to 70 %). In Eukaryotes, the Plasma membrane is made up of Carbohydrates and Streols (Cholesterol). —   Generally, Plasma membrane is a Phospholipid bilayer and Semipermeable.   —   The Phospholipid structure is Amphipathic (a molecule, especially Protein, having both Hydrophilic and Hydrophobic parts) in nature and measures approximately 8 nm thick. —   The Phospholipid structure has Hydrophilic (water loving) heads and Hydrophobic (water hating) tails.   Structure of Phospholipid FLUID-MOSAIC MODEL STRUCTURE OF PLASMA MEMBRANE —   The dynamic arrangem