chapter 4 micro

what is the cytoplasmic matrix

substance in which nucleoid, ribosomes, and inclusion bodies are suspended

• aqueous environment

what are inclusion bodies

granules of organic or inorganic material that are stored by the cell for future use

• some are enclosed by a single layer shell

what are some of the organic materials that are saved in inclusion bodies

glycogen

• polymer of glucose unit

poly-b-hydroxybutyrate (PHB)

• used to produce biodegradable plastics

cyanophycin granules

• large polypeptides

carboxysomes

• used for CO2 fixation

what do gas vacuoles do and what are they found in

found in cyanobacteria and other aquatic prokaryotes

provide buoyancy

• have cylindrical structures with a protein shell that is permeable to gas but not water

magnetosomes

stores particles of iron oxide or iron sulfate

• used for magnetic sensing to orient bacteria

prokaryotic cell wall variations

some bacteria dont have cell walls

• mycoplasmas

archaea has many types of cell walls but that all lack peptidoglycan

• some have pseudopeptidoglycan

gram positive stain

retain purple coloration

• thick peptidoglycan cell wall (20-80 nm thick)

gram negative stain

lose purple color when washed

• have 2-7 nm thick peptidoglycan layer that’s covered with 7-8 nm thick outer membrane

what does the cell envelope contain (5)

plasma membrane

outer membrane (when present)

cell wall

periplasmic space

capsules and other structures exterior to the cell wall

where does the periplasmic space extend to for gram positive and negative bacteria

positive - from cellular membrane to cell wall

negative - from cell membrane to outer membrane

what is peptidoglycan

mesh like polymer that is composed of identical subunits

• chains of subunits are cross linked

  • this provides extra strength and rigidity

what is the gram negative cell envelope made of

consist of thin layer of peptidoglycan surrounded by outer membrane

• outer membrane is composed of lipids, lipoproteins, and lipopolysaccharides

no teichoic acids

characteristics about gram negative cell envelope (3)

more complex than gram positive
periplasmic space takes up more space of the cell
many enzymes are present in this space

what do lipoproteins and lipopolysaccharides do in gram negative cell envelopes

lipoproteins connect the outer membrane to the peptidoglycan layer

lipopolysaccharides take the role of phospholipids in the outer layer of the outer membrane and project out from its surface

what are the 3 parts of a lipopolysaccharides

lipid A

core polysaccharide

O side chain

what do lipopolysaccharides do (3)

contributes to negative charge on cell surface

helps stabilize outer membrane structure

acts as an endotoxin

what are the layers of materials lying outside the cell wall called (2)

capsules and slime layers

what is the difference between capsules and slime layers

capsules are not easily removed from the cell where slime layers are

what are S-layers and what organisms are they common in

regularly structured layers of protein or glycoproteins

• external to cell wall

  • common in archaea

functions that capsules, slime layers, and S-layers share

protection from host defenses (phagocytosis), protection from environmental conditions, attachment to surfaces

how many parts of a flagella are there

3
filament, hook, and basal body

what is the filament part of a flagella

extends to exterior

made of proteins called falgellin

what is the hook part of a flagella

what connects the filament to the cell

what is the basal body of a flagella

anchors the flagella to the cell wall

what is the major pathway for bacterial protein secretion regardless of gram stain type

the Sec-dependent pathway

what does the Sec-dependent pathway do

takes proteins from the cytoplasm across or into the plasma membrane

• initially synthesized as preproteins that contains an amino terminal signal peptide

what happens when the preprotein emerges from the other side of the plasma membrane

a signal peptidase comes and removes the signal peptide