MCB 2610: Exam 3 pt. 1

gram stain in 1884 was done by?

Hans Christian Gram

one major difference between gram positive cell wall and gram-negative cell wall?

gram positive has larger peptidoglycan layer

components of gram-positive cell wall?

thick peptidoglycan layer (cell wall), narrow periplasmic space, plasma membrane, no outer membrane

components of gram-negative cell wall?

larger periplasmic space, outer membrane & peptidoglycan (cell wall), plasma membrane

what is in the peptidoglycan in gram-positive cells?

teichoic acids

teichoic acids are just in peptidoglycan or reach down to plasma membrane?

just in peptidoglycan

lipoteichoic acids are just in peptidoglycan or reach down to plasma membrane?

reach down to plasma membrane

approximately how many sheets of peptidoglycan is in gram-positive cells?

3-20 sheets

does peptidoglycan have channels, transporters, pores, etc.?

no but it has a size inclusion rule and allows larger molecules to move through

lipoteichoic acid and teichoic acid have a positive or negative charge?

negative charge which contributes to net negative charge

teichoic acid is connected __ to peptidoglycan

covalently

teichoic acid are polymers of?

glycerol or lipotol joined by phosphate groups

lipoteichoic acids have lipids on?

end allowing for embedment in plasma membrane

what embedding in plasma help prevent?

netting of peptidoglycan from floating away

outer membrane of gram-negative cells is single layer or bi-layer?

bi-layer

outer portion of outer membrane of gram-negative cells are composed of?

lipopolysaccharide

lipopolysaccharides are made up of?

lipids and sugars

the periplasmic space in gram-negative cells takes up about how much total volume?

20-40%

how many peptidoglycan layers are there in gram negative envelope?

1-2

what is the most abundant protein in outer membrane in the gram negative envelope?

braun's lipoprotein

braun's lipoprotein

links membrane and envelope to rest of bacterial cell

lipids in lipopolysaccharide have longer or shorter fatty acids than in inner leaflet?

shorter

does outer membrane contain transport proteins in gram-negative envelope?

yes

lipopolysaccharide - 3 parts?

Lipid A, core polysaccharide and o-antigen

lipid A

most closely associated with inner leaflet of outer membrane

lipid A is a rigid molecule and its rigidity helps?

stabilize

core polysaccharide

short string of sugars

o-antigen

largest part; most outwards facing towards outer environment; o-side chain

o-side chain is made up of approximately?

200 sugars

core polysaccharide is made up of what kind of sugars?

possibly peptose

what can be found floating around in periplasmic space?

proteins

the proteins floarting around in periplasmic space are involved in?

nutrient acquisition (hydrolytic enzymes)

enzymes are involved in?

transport, energy conservation and detoxifying substances

polysaccharide = ?

sticky

importance of lipopolysaccharide (LPS)

contributes to negative charge on cell surface or may contribute to attachement to surfaces/biofilm formation, helps stabilize outer membrane, creates permeability barrier, protection from host defenses and acts as endotoxin,

o-side chains make it difficult for eukaryotes to?

phagocytize bacteria which won't be destroyed if it isn't pagocytized

what's another way (LPS) o-side chains can protect against host defenses?

if they change their sugars immune response no longer recognizes it and doesn't work

endotoxin is sequestered in?

bacteria cell itself

what portion of LPS acts as endotoxin itself and why?

lipid A because it contains a pamp (pathogen associated molecular pattern)

when lipid A is embedded in inner leaflet it doesn't do anything but when cells are killed are in a less than orderly fashion lipid A can?

be released from cell causing endotoxin to be exposed to environment

porin proteins are apart of what kind of diffusion?

facilitated

in gram-negative; small things can use what kind of diffusion?

simple diffusion

porin proteins in E. coli are more permeable than plasma membrane due to?

presence of porin proteins and transporter proteins

porin proteins are not as specific and are they open on both sides?

yes

carrier proteins are more specific and are they open on both sides?

not always

carrier proteins bind to specific molecules and are used in what kind of diffusion?

facilitated diffusion; non-energy dependent

gram-positive peptidoglycan is considered porus meaning?

things can just make its way through through large pores throughout the matrix

gram-negative cell has __ and __ proteins in its outer membrane to transfer molecules into the periplasmic space

porin, TonB

why do gram-negative cells have to be able to active transport?

because they are usually found in low nutrient concentration environments

what kind of transport systems do we have in outer membrane?

primary, secondary and group-translocation active transport systems

some move things from periplasm to outside directly and they are known as?

autotransporters, rare

autotransporters embed themselves in PM and?

pull themselves through

some use single-step (never entering the __) transport system

periplasm

single step transport systems include?

type I and type II systems

sec & tac - how do we use them?

go across PM, drop off in periplasm and then use more sec and tac to move to outer membrane

mechanism of gram stain reaction - large pores in the gram __ cells shrink

positive

mechanism of gram stain reaction - some outer membrane lipids that crystal violet binds are stripped in the gram __ cells

negative

what are some of the similarities between gram positive and gram negative cell walls?

both have peptidoglycan, a negative charge and periplasmic space

what are some of the differences between gram positive and gram negative cell walls?

peptidoglycan in different amounts, periplasmic size differences, gram pos. negative charge comes from teichoic/lipoteichoic acid and gram neg.'s comes from outer membrane in LPS in terms of phosphates associated with core and neg. charged sugars & phosphates associated with lipid A

one more difference in gram pos vs gram neg.

no transporters in gram pos b/c of no outer membrane