Chapter 1 Identify the cellular components and some of the protein components of the blood/immune system. Background information Bacterial cell wall structures · Bacteria live in a hypotonic environment ( [solute] inside cytoplasm is greater than the [solute] in the environment. Water from the environment would spontaneously flow across the membrane and into the cytoplasm .-- > because the phospholipids of the membrane are not covalently bonded together, the bacterial cells can swell and burst due to the osmotic flow of water. · Bacterial membranes are stabilized by cell walls, which also allow the bacteria to be divided into two groups: gram-positive and gram-negative (these terms refer to the ability of the cell walls to retain a particular stain) o Gram positive cell walls are composed primarily of PG ~20 layers. Other structures such as cell wall proteins and teichoic acid may poke through the PG mesh. Some cell wall proteins may be involved in attachment to surfaces. A phagocytic cell may engulf a gram-positive bacteria after its phagocytic receptors bind to a cell wall protein. The phagocytic cell may then recognize it as danger when a TLR recognizes the PG structure of the cell wall. o Gram-negative bacteria have a slightly more complicated cell wall structure . 1-2 layers of PG and an additional membrane layer (outer membrane) external to the PG . o The outer membrane is a bilayer composed of phospholipids, lipopolysaccharides (LPS- composed of lipids and polysaccharides and is only found in gram-negative bacteria), lipoproteins and porins. · Peptidoglycan (PG) is a huge mesh like structure made of o Glycan chains: made of sugars that are synthesized by the bacteria o Tetrapeptide: structures that cross-link the glycan chains · PG provides mechanical strength to the bacterial membrane to protect it from osmotic lysis due to the covalent bonds that link the sugars of the glycan chains and covalent bonds of cross- linking tetrapeptides
Gram-positive cell wall Gram-negative cell wall surface proteins 8 teichoic acid porin 8 lipoteichoic acid ) protein protein LPS O polysaccharide lipid A outer membrane 8 . peptidoglycan NAM NAG lipoprotein peptidoglycan poptide cytoplasmic membrane cytoplasmic membrane phospholipid phospholipid http://faculty.ccbcmd.edu/courses/bio141/lecguide/unit1/prostruct/gpcw.html The body has three levels of defense against infection. 1. The anatomical and physiological barriers include: o intact skin provides a physical barrier, o mucosal surfaces of the gut, respiratory urogenital and conjunctivae surfaces, o stomach acid, lysozyme and other antimicrobial body secretions. 2. The innate immune responses (non specific) are the initial internal defenses. Immediate: this involves performed proteins in the blood/tissues and phagocytic cells already in tissues o Induced: involves the recruitment of phagocytic cells from the bloodstream and into the tissue (site of infection) These responses are: o quick and non-specific, o involves phagocytosis and activation of the complement proteins, o limits the spread of infection, o often resolves the infection. o Examples: skin, mucusm lysozymes in eyes, acid in stomach 3. The adaptive immune responses are the last line of defense. These responses are: o slower to respond but