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CH.3 PROKARYOTIC CELL STRUCTURE (General characteristics (mostly water,…
CH.3 PROKARYOTIC CELL STRUCTURE
General characteristics
mostly water
proteins/DNA/RNA 24%
cell envelope 5%: peptidoglycan (cell wall) + membrane phospholipids + lipopolysaccharides
other: metabolites +inorganic ions + polyamines
model of bacterial cell
cytoplasm: proteins, RNA, macromlcls, water, inorganic ions, nucleoid: DNA, ribosomes, plasmids, inclusions
external structures: pili/fimbriae, flagellum/flagella, capsule surr cell wall
inner cell membrane: phospholipids bilayer+ proteins (transport, enzymes) + maintain gradients
functions: separates cytoplasm from external medium & contains many proteins w/ specific functions
membrane protein functions: structural support + detect environ signals + ion transport/energy store + secrete communication & virulence factors + hopanoids reinforce cell membrane
environment can change membrane lipid structure
phospholipid head group & fatty acid chain type & length
saturation/unsaturation of fatty acids
cyclization of fatty acid chain (cyclopropane)
archaebacterial membrane lipids
hydrocarbon chains are terpenoids (from isoprene)
ether link (COC) hydrocarbons to glycerol VS ester linkage in bacterial phospholipids (COOC)
cyclization to cyclopentane
adapt to high temps (thermo and hyperthermophiles) by eliminate/reduce kinks so more saturation -> reduce space for havoc
cell walls: made of peptidoglycan (sugar peptide polymer)/ murein: function for structural support + protection + porous
Gram-positive bacteria
thick cell wall
teichoic acids
Gram-negative bacteria
thin cell wall
outer cell membrane
lipopolysaccharide layer (LPS)
virulence factors
more susceptible to lyse in hypotonic soln
polymer disaccharide, glycan, cross-links with peptide tetramers
can form sacculus: cell wall from rod-shaped bacteria