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