Chapter 3 (Notes) Cell Envelope Flashcards
number of microbes
10^31
microbe size range
0.2 micrometers to 1 millimeter
prok 0.5-5 micrometers
euk 3 micrometers - 1 mm
microbes were first referred to as…
bags of chemicals
4 important structures of a bacterial cell
cell wall
cell membrane
cytoplasm
nucleoid region
cytoplasm contains _________
microcompartments full of ions and small molecules
nucleoid region
where genome is located
bacterial cells are _______ but flexible, and are tightly ______
ordered, controlled
gene regulation in response to the environment
phospholipid bilayer components (amphipathic)
polar head - phosphatidate
glycero-
fatty acid chain (ester linkage)
marine cyanobacteria may have alternative lipids like…
phosphatidylglycerol (PG)
SQDG
archaeal cell memb
isoprene hydrophobic tails attached to glycerol by an ether
sometimes a lipid monolayer, not bilayer (more stable at higher T)
weak acids and weak bases exist partly in an ________ form that can _______ across the membrane and change the __ of the cell
uncharged, diffuse, pH
polar molecules and charged molecules require transport through protein ________
transporters
in passive transport molecules move which way
down [ ] gradient
in active transport molecules move which way
against their [ ] gradient
requires energy
hopanoids add ________ to membranes
strength
like sterols for bacteria… maintain rigidity
biochemical makeup
70% water (typical of all cellular life)
essential ions: Na, K, Cl, H
macromolecules: protein, nucleic acid carbohydrate, lipid
metabolites: things the cell is making (intermediate or final product)
polyamines:
ratios of biochemicals in a bacterial cell
water 70%
protein 16%
RNA 6%
phospholipids 3%
everything else .1 - 1%
_______ are the most diverse class of molecules in the cell
proteins
polyamine
organic molecule with many aa
stabilize neg charged DNA
regulate pH
the cell wall is made of ________
peptidoglycan (murein)
beta 1,4-glycosidic bondh
in peptidoglycan, the ______ chains of ____ and ____ are crosslinked to each other by short ______
glycan (sugar), NAM (n-acetylmuramic acid), NAG (n-acetylglucosamine), peptides
function of cell memb. cell wall
barrier btw inside and outside
selectivity - passive/active transport
maintain turgor pressure
high tensile strength and elasticity
attachment point
energy storage via electrochemical gradient (proton motive force)
turgor pressure of gram neg and gram pos
gram neg: 2-5 atm
gram pos: less than 20 atm
what does high tensile strength do
allow for strength and flexibility
how are leaflets held together
hydrophobic interactions
is the molecule makeup of cross-bridges in peptidoglycan species specific?
yes, results in different strengths and rigidities of the cell wall
are multiple layers or peptidoglycan (murein) cross linked?
yes
transpeptidase
bacterial enzyme that cross-links peptidoglycan chains to form layers
beta-lactam antibiotics (penicillin)
irreversibly binds to and inhibits transpeptidase (acetylate serine in active site)
turgor pressure then lyses cells
aka. penicillin binding protein
lysozyme
human body’s own antibiotic
found in tears
breaks the beta 1,4-glycosidic bond in peptidoglycan
beta-lactamase
some bacteria have this enzyme that cleaves the ring structure of beta-lactam antibiotics
makes bacterium resistant to beta-lactam antibiotics
evolutionary adaptation
gram stain (differential stain)
distinguish btw gram pos and gram neg b/c of different cell wall structures
gram neg: thin cell wall with 1-2 layers or peptidoglycan enclosed by outer memb with LPS
gram pos: thick cell wall with 3-20 layers of peptidoglycan w/ teichoic acids
how to do a gram stain
purple crystal violet stain
rinse w/ ethanol (gram pos resistant and stay purple)
pink saffranin counterstain makes gram neg pink
lipopolysaccharide (LPS)
found in gram neg
main outward facing phospholipids
acts as an endotoxin (released when lysed)
teichoic acid
found in gram pos
net negative charge allow binding of cations and attachments to pos charged surfaces
attachments for bacteriophage
varying length depending on species
acid-fast bacteria have a different cell ____ that contains ______ acids
wall, mycolic acids
hard to characterize using standard techniques (eg. gram stain)
mycoplasms are cell ____-less bacteria
cell wall-less bacteria
membrane strengthened by sterols
eg. mycoplasma pneumoniae - bacterial “walking” pneumonia
4 ways archaeal cell walls vary
some dont have cell walls; have cell memb. made of lipoglycan
some have simple s-layers made of glycoproteins
some have rigid cell walls of polysaccharide
some have pseudopeptidoglycan with L aas and NAG/NAT backbone with beta 1,3 linkages
eukaryotic microbes possess their own structures to avoid _______ shock
osmotic
algae - cell walls of cellulose
fungi - cell walls of chitin
diatoms - exoskeletons of silicate
paramecia - contractile vacuole to pump water out
can ions diffuse passively through the memb?
no, allows for electrochemical gradient (and maintain pH)
what small molecules can diffuse through memb
O2
CO2
N2
H2O
large molecules are _______ transported
actively
some can diffuse passively
where is a cell envelope located
outside the membrane
2 main glycerols
NAM n-acetylmuramic acid
NAG n-acetylglucosamine
LPS 3 parts of structure
o-specific chain (o-antigenic repeating subunits)
core (endotoxin)
lipid A
ex. E. Coli O157:H7 (O antigen + H-antigen from flagella)
