bacte Flashcards
Form small hydrophilic channels through the outer envelope allowing the diffusion neutral and charged solutes of MW <600 daltons ● Three identical units ● Associate to form membrane holes
porins
mediate interconnection between the OM and murein ● synthesized within the cell and contains a leader sequence of 20 amino acids at its amino terminal end ● after transport through the CM, the leader sequence is removed and the terminal residue is modified to make it hydrophobic > − facilitates integration into the OM
lipoproteins
proteins in OM are used as attachment sites by ______
bacteriophages
outer surface bacteria’s outer membrane with strong negative charge is important in evading ______________
phagocytosis
bacterial endotoxin causing a variety of pathophysiological reactions ranging from fever to death
LPS complex
A separate compartment between the cell membrane and outer membrane in Gram (-) bacteria
periplasm
activities of periplasm
activites: ● redox reactions ● osmotic regulation ● solute transport ● protein secretion ● hydrolysis
thought to be involved in the osmotic regulation of the periplasm because their amounts decrease when the cells are grown in media of high osmolarity
oligosaccharides
bind to solutes and deliver solutes to specific transporters in the membrane
solute binding proteins
degrade nutrients to smaller molecules that can be transported across the membrane by specific transporter
hydrolytic enzymes
required for the uptake of several solutes (iron siderphores, vit B,2) that do not diffuse through the porin
TonB Proteins
●Most dynamic structure of a prokaryotic cell
● Definitive structure of the cell
● Has a variety of functions in energy generation and biosynthesis
● Contains transport proteins, binding proteins, sensing proteins and enzymes involved in metabolic processes
● Absolute requirement of a living organisms
● Chief point of contact with the environment
plasma membrane
most membrane associated lipids are structurally assymetric
phospholipids
For every 1 g of cells:
91 mg phospholipid
129 umole phosphatidylethanolamine
where: 1 umole = 750 ug PE
● major phospholipid in the cytoplasmic membrane
● formed from glycerol-3-P, serine and fatty acids in the ratio of 1:1:2
phosphatidylethanolamine
● next most prevalent
● formed from glycerol-3-P and fatty acids in equimolar ratios
phosphatidylglycerol
two types of membrane proteins
integral proteins
peripheral proteins
- embedded in the CM
- amphipathic
- bound to the fatty acids of the phospholipids via hydrophobic bonding
integral proteins
attached to membrane surfaces by ionic interactions
peripheral proteins
most widely accepted model of the cell membrane
shows that the cell membrane is a lipid bilayer with which proteins and lipids “float”mfreely
Fluid Mosaic Model
consists of aqueous solution
a. macromolecules
b. small molecules which serve as energy sources, precursors of macromolecules, metabolites or vitamins
c. various organic and inorganic ions and cofactors
cytoplasm
structural components of bacteria’s cytoplasm
nucleoid
ribosomes
inclusion bodies
cytoskeletal filaments are structurally similar to their eukaryotic counterparts
prokaryotic cytoskeleton
FtsZ (tubulin)
cell division
MreB (actin)
cell shape
Cresentin (intermediate filament proteins)
cell shape
invaginations of the plasma membrane in the shape of vesicles, tubules or lamellae
believed to be involved in cell septum formation electron transport, photosynthesis, cell wall formation, DNA replication and segregation and sporulation
Mesomes
distinct bodies that may occupy a substantial part of the cytoplasm
may be organic or inorganic
some inclusion bodies lie free in the cytoplasm or enclosed by a shell consisting of proteins or a membranous structure composed of proteins and phospholipids
usually used for storage
inclusion bodies
a polymer of glucose units composed of long chains formed by a 1,4 glycosidic bonds and branching chains connected to them by a 1,6 glycosidic bonds.
glycogen
contains b-hydroxybutyrate molecules joined by ester bonds
poly-b-hydroxybutyric acid (PHB)
composed of large polypeptides containing approximately equal amounts of amino acids arginine and aspartic acid
cyanophycin granules
polyhedral bodies about 100 nm in diameter
contain the enzyme ribulose-1,5-bisphosphate carboxylase
may serve as site for CO, fixation
carboxysomes
ellipsoidal vesicles where photosynthetic pigments are located
attached to the plasma membrane but not continuous with it
chromosomes
linear polymer of orthophosphates joined by ester bonds
function as storage reservoirs for phosphates or as energy reserve
polyphosphate granules (volutin or metachromatic granules)
used to store sulfur temporarily
accumulate in the periplasmic space of in special cytoplasmic globules
sulfur granules
small, hollow, cylindrical structures composed entirely of a single small protein
impermeable to water but freely permeable to gases
gas vesicles
intracellular chains of magnetite (Fe3O4), greigie (Fe3S4) or pyrite (FeS2) particles bounded by a membrane
aids in orienting bacteria in the earth’s magnetic field
Magnetosomes
