Chapter 3 Flashcards
Cell Envelope
The layers surrounding the contents of the cell:
- Glycocalyx
- Cell Wall
- Cell Membrane
Glycocalyx
A slimy substance that adheres to the outside of the cell wall:
- Protects the cell from dehydration
- Allows bacteria to attach to tissue, which can then be invaded
- Protection against phagocytosis by white blood cells, increasing survival rate
- Retards the staining process
Capsule
A distinct thick gelatinous material that surrounds some types of microorganisms; sometimes required for an organism to cause disease; type of glycocalyx
Slime Layer
Type of glycocalyx that is diffuse (thin) and irregular
Mycoplasma
Genus of bacteria that lack cell walls; pump ions (Na+) out of the cell to keep turgor pressure equal inside and outside - prevents lysis; cell membranes strengthened by cholesterol
Cell Wall
A rigid structure that maintains cell shape and provides protection from the environment (e.g., low levels of heat, chemicals); provides protection from osmotic pressure
Lysis
The swelling and bursting of a cell
Penicillin
Antibiotic that interferes with the synthesis of the peptidoglycan portion of bacterial cell walls; binds to and inactivates the enzymes responsible for resealing breaks in the cell wall, causing lysis
Lysozyme
An enzyme found in tears that digests (breaks down) peptidoglycan
Gram-Positive Cell Wall
Thick, homogenous sheath of petidoglycan (20-80 nm thick) that forms about 90% of the cell wall; retain crystal violet stain (purple)
Peptidoglycan
Macromolecule found only in bacteria that provides strength to the bacterial cell wall; composed of alternating glycan molecules and tetrapeptide chains (4 amino acids long); contains teichoic acid
Glycan Molecules
A simple sugar (glucose) connected to an amino acid (amino sugar)
- NAG (N-acetylglucosamine)
- NAM (N-acetylmuramic acid)
- Forms a mesh-like structure
- Alternating sugars form numerous layers (up to 30 layers thick)
Tetrapeptide Chain
Each layer of carbohydrates are connected by amino acids or peptides (NAM); exact amino acids vary between species (Gram+ cells)
Teichoic Acid
A complex molecule that contains amino acids, sugars, glycerol, and phosphate molecules; used as structural material; travels from the cell membrane through the cell wall, connecting them (Gram+ cells)
Gram-Negative Cell Wall
Thin layer of peptidoglycan (1 layer thick, 5-20% of cell wall) surrounded by an outer membrane; 2 layers - periplasmic space and outer membrane; stain pink
Periplasmic Space
A region between the cell membrane (inner) and the outer membrane in Gram-negative bacterial cells
Periplasm
Gel-like material that fills the periplasmic space
Outer Membrane
Bilayer of Gram-negative cells that surrounds the peptidoglycan layer:
- Layer of phospholipids and macromolecules which serves as a selective barrier for some small molecules to pass
- Layer of Lipopolysaccharides (LPS) which forms the outer sheath of the membrane
Lipopolysaccharide (LPS) or Endotoxins
A molecule formed by bonding lipid to polysaccharide; can be toxic to the human body; different types can be used to identify different strains or species of bacteria
Porin Proteins
Proteins embedded in the outer membrane that allow specific molecules to pass and will shut off when the cell is threatened; makes antimicrobial agents less effective against Gram-negative bacteria
Cell Membrane
Serves as a barrier to molecules (selectively permeable); composed of a phospholipid bilayer (40%) with proteins (60%) embedded in the bilayer; hydrophobic fatty acid tails and hydrophillic phosphate heads
Carrier Protein
Bind to specific substances and transport them across the cell membrane
Channel Protein
Opening which allows small, water soluble substances to go across the cell membrane
Selectively Permeable Membrane
Prevents the entrance or exit of certain molecules (large molecules, molecules not soluble in fat, except for water)
