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Chapter 3

Cell Wall

Q: What gives the cell wall of bacteria its rigidity? A: Peptidoglycan (PTG)
Q: What is the basic structure of peptidoglycan (PTG)? A: An alternating series of two subunits, N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), which form two glycan chains. The two glycan chains are held together by a string of four amino acids.
Q: The cell wall of gram positive bacteria is made up of how many layers of peptidoglycan (PTG)? A: As many as 30 layers making it a thick cell wall.
Q: What gives a bacterial cell its negaive charge? A: Teichoic acid.
Q: The cell wall of gram negative bacteria is made up of how many layers of peptidoglycan (PTG)? A: Two to three layers making it a thin cell wall.
Q: The peptidoglycan (PTG) of gram negative bacteria can be found where? A: In a region between the outer membrane and the cytoplasmic membrane know as the periplasm.
Q: True or false? In gram positive bacteria peptidoglycan (PTG) is sandwiched between an outer membrane and the cytoplasmic membrane. A: False! This is true only of gram negative bacteria.
Q: Aside from the cell wall, what can be found in the periplasm? A: Secreted proteins and proteins of the ABC transport system.
Q: The cell wall of gram negative bacteria has an outer membrane. What is it made of? A: The outer membrane (aka lipopolysaccharide layer or LPS layer) is a lipid bilayer made up of lipopolysaccharides.
Q: The outer membrane of the cell wall in gram negative bacteria serves as a barrier to large molecules but allows small molecules and ions through channels called _______. A: Porins.
Q: The outer cell membrane of gram negative bacteria has two portions, an inner and an outer. What are these portions called? A: The inner portion is “Lipid A” and the outer portion is called an “O-specific polysaccharide side chain”.
Q: True or false? Lipid A is considered an endotoxin. A: True!
Q: Whay are gram negative infections considered deadly? A: Because lipid A is an endotoxin.
Q: What anchors lipopolysaccharide molecules in the lipid bilayer and plays a role in recognition of infection? A: Lipid A.
Q: Which part of the outer membrane is used to identify certin species or strains? A: The O-specific polysaccharide side chain.
Q: True or false? Many antimicrobials, such as Penicillin and Lysozyme, interfere with the synthesis of peptidoglycan (PTG). A: True!
Q: Is Penicillin better against gram positive or gram negative bacteria. A: Penicillin is more effective against gram positive due to increased concentration of peptidoglycan (PTG).
Q: Penicillin is completely ineffective against gram negative bacteria. A: False! There are Penicillin derivatives produced to protect against gram negative bacteria.
Q: Name two places where lysozymes are produced. A: Lysozymes are produced in many body fluids including tears and saliva.
Q: What does a lysozyme do? A: Lysozymes destroy the integrity of the cell wall by breaking the bond linking NAG and NAM.
Q: Two examples of a lysozyme given in class were _______ and _______. A: Protease and nuclease.
Q: What accounts for differences in staining characteristics of gram negative and gram positive bacteria? A: The cell wall.
Q: When using a Gram stain, gram positive bacteria will stain _______ and gram negative bacteria will stain ______. A: Gram positive will be purple and gram negative will be pink.
Q: True or false? All bacteria have a cell wall. A: False! Some bacteria naturally lack a cell wall.
Q: If a bacterium lacks a cell wall, what is responsible for maintaining the cell shape? A: Sterols in the membrane.
Q: Give an example of a bacterium without a cell wall. A: Mycoplasma.
Q: Does Penicillin have any effect on mycoplasma? Why or why not? A: No, because mycoplasma have no cell wall.
Q: True or false? Bacteria in domain Archae contain peptidoglycan. A: False! Bacteria in domain Archae have a wide variety of cell wall types but NONE contain peptidoglycan (they contain pseudo-peptidoglycan).
Q: What causes the mild form of pneumonia known as "walking pneumonia"? A: Mycoplasma
Q: Together, the two layers outside the cell wall are referred to as ______? A: Glycocalyx (glyco = sugar / calyx = shell).
Q: There are two layers external to the cell wall of bacteria. What are they? A: The capsule and the slime layer.
Q: True or false? Bacterial capsules are a distinct gelatinous layer. A: True!
Q: True or false? Bacterial slime layers are irregular diffuse layers. A: True!
Q: Chemical composition of capsules and slime layers varies depending on bacterial species but most are made up of _______. A: Polysaccharide.
This MICROBIOLOGY stack covers the section of chapter 3 entitled CELL WALL. (blank)
Created by: PCC Microbiology