Revision from 1st year micro

Revision from 1st year micro

1. Prokaryotic cell

   • small, simple primitive intracellular structure. It has a circular chromosome and a peptidoglycan cell wall

2. Eukaryotic cell

   • Large/complex molecule with an internal membrane and membrane bound organelles. They have a linear chromosome and a cell envelope or rigid cell wall

3. Gram Staining

   • Gram Positive
     • Has a thick multilayered cell wall and cytoplasmic membrane. The cell wall retains cell integrity under high osmotic pressure. There is no second lipid membrane.
   • Gram Negative
     • Thin inner layer of peptidoglycan, which is then covered by an outer membrane. The cell wall is a rigid barrier composed of a repeated polysaccharide structure.

4. Cell Wall Structure

   • Controls movement across the membrane (structural barrier). Detergents and water baths damage the membrane which screws up the process in bacteria which means it can't recover. It is also a surface for chemical reactions. It determines where the cytoplasm ends and the external environment starts.
   • The inner layer of the cell wall is made of peptidoglycan and is covered by an outer membrane that varies in thickness and chemical composition depending upon the gram staining property of the bacteria. The peptidoglycan layer is much thicker in gram positive bacteria.
   • The peptidoglycan sugar chain is cross linked by amino acids. Peptide forms cross bridges. It is a rigid structure. IT can lead to a vulnerability for micro-organisms as if it doesn't work then lysis can occur

5. Lipopolysaccharide