Structure and Function
energy conservation
site of generation and use of proton motive force
50% or less
the ratio of proteins to lipids in the membrane
sensors
membrane proteins that function as markers for cellular identification
enzymes
membrane proteins whose fixing to membranes localises metabolic pathways
adhesins
membrane proteins that serve to connect and join two cells together
luca
last universal common ancestor
metabolism
cells take up nutrients, transform them, and expel wastes
genetic metabolism
replication, transcription, translation
catalytic metabolism
energy, biosyntheses
growth
nutrients from the environment are converted into new cell materials to form new cells
evolution
cells evolve to display new properties. relationships captured by phylogenetic trees
differentiation
some cells can form new cell structures such as a spore
communication
cells interact with each other by chemical messengers
genetic exchange
cells can exchange genes by several mechanisms
motility
some cells are capable of self-propulsion
metabolism, growth, evolution
properties of all cells
differentiation, communication, genetic exchange, motility
properties of some cells
surface to volume ratio
a relationship in which the volume of an object increases with the cube of the diameter, and the surface area increases with the square
permeability barrier
prevents leakage and functions as a gateway for transport of nutrients into, and wastes out of, the cell
protein anchor
site of many proteins that participate in transport, bioenergetics, and chemotaxis
transporters
membrane proteins responsible for facilitated diffusion and active transport
integral membrane proteins
proteins that are at least partially embedded in the plasma membrane
hydrophobic groups
phospholipid tails
hydrophilic groups
phospholipid heads
2 fatty acids, 1 glycerol, 1 phosphate group
phospholipid structure
phospholipid bilayer
a double layer of phospholipids that makes up plasma and organelle membranes.
isoprene
C5H8. alkyl chains are linked to G1P in archaea
phosphatidyethanolamine
a glycerophospholipid with an ethanolamine head group. plays a role in the assembly of membrane proteins
glycerophospholipids
phospholipids that contain a glycerol backbone
HO-CH2-CH2-NH3+
ethanolamine
ester bonds
link fatty acids to glycerol-3-phosphate in bacterial and eukaryotic membranes
ether linkages
link isoprene alkyl chains to glycerol-1-phosphate in archaea
glycerol diether
produces lipid bilayer, some membranes a mixture of monolayers and bilayers
diglycerol tetraether
produces a lipid monolayer, typically extremely resistant to heat denaturation, found in hyperthermophiles
crenarchaeol
one of the lipids comprising the archaeal lipid monolayer; contains cyclic steroid-like functional groups
phytanyl
isoprene polymer in the plasma membrane of some archaeons; 20-carbon hydrocarbon
biphytanyl
isoprene polymer in the plasma membrane of some archaeons; 40-carbon hydrocarbon forming a phospholipid monolayer
sterol
a lipid that stabilises the lipid bilayer, consisting of a polar head, a rigid planar steroid ring structure and a non-polar hydrocarbon tail. eukarya
cholesterol
sterol in animal cells
ergosterol
sterol in fungi
stigmasterol
sterol in plant cells and some protozoans
bacteria, archaea
organisms that sterols are almost always absent
hopanoids
structurally similar to sterols. present in membranes of many bacteria
bacteria, archaea
circular, double-stranded, haploid, protein packaging forms nucleoid, DNA in cytoplasm, ribosomal RNA encoded on chromosome, plasmids
eukarya
linear, double-stranded, diploid, protein packaging forms chromatin fibers, DNA in nucleus, nucleolus
ribosome
composed of ribosomal RNA and proteins, translates mRNA into amino acid chains to form proteins
70S ribosome
prokaryotic ribosomes free in the cytoplasm or attached to cytoplasmic membrane. 30S + 50S subunits
80S ribosome
eukaryotic ribosomes free in the cytoplasm or bound to the endoplasmic reticulum. 40S + 60S subunits
svedberg unit
describes the sedimentation rate of a particle in an ultracentrifuge. proportional to size, shape and density of particle but relationship is non-linear
eukaryotic cell wall
surrounds cell of plants, algae, fungi. absent in animals and most protozoa. forms a tough, rigid barrier that helps protect the cell and give its shape
polysaccharides
compose the eukaryotic cell wall
cellulose
polysaccharide that composes the cell wall in plants, algae and some fungi. polymer of glucose
chitin
polysaccharide that composes the cell wall in fungi. polymer of N-acetylglucosamine
euchromatin
loosely packed chromatin. actively transcribed
heterochromatin
densely packed chromatin. low level of transcription
mRNA for cytoplasmic proteins
ribosome-mRNA complex stays free in cytoplasm
mRNA for membrane proteins, secreted proteins, vesicular proteins
ribosome-mRNA complex is directed to the endoplasmic reticulum
endoplasmic reticulum
a system of membranous channels. membrane is composed of a phospholipid bilayer
rough endoplasmic reticulum
studded with ribosomes, important for protein synthesis
smooth endoplasmic reticulum
no ribosomes, involved in synthesis of lipid
golgi body
a set of membrane compartments involved in further processing of proteins and their distribution
vesicles
small membrane sacs that package proteins and transport them where they need to be
lysosomes
internal vesicles that contain hydrolytic enzymes to degrade materials brought in by phagocytosis and endocytosis
mitochondria
produce most of the ATP required by the cells. absent in some protozoa
outer mitochondrial membrane
many porin proteins, very permeable to small molecules
inner mitochondrial membrane
75% proteins, 25% lipids. transport proteins, enzymes, cytochromes, ATPases
mitochondrial matrix
the fluid inside the inner membrane of a mitochondrion. enzymes, circular DNA, 70S ribosomes
outer chloroplast membrane
contain porins, similar to mitochondria
inner chloroplast membrane
contain transport proteins (regulated transport)
thylakoids
a closed system of interconnecting sacs and tubules containing enzymes and pigments that harvest light energy and membrane-bound ATPases that use energy to produce ATP
stroma
circular DNA, 70s ribosomes, Calvin cycle enzymes
keratin
intermediate filament in skin that provides resistance mechanical stress
desmin
intermediate filament in muscle cells
vimentin
Intermediate filament in connective tissue
actin filaments
protein fibers that play a role in cell division and shape. can be polymerised and depolymerised by changing filament length
intermediate filaments
a component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments
microtubules
spiral strands of protein molecules that form a tubelike structure. made of alpha and beta tubulins. provide transport highways within the cell
eukaryotic cytoskeleton
a complex network of protein filaments in the cytoplasm that helps organise the cytoplasm and give the cell its shape
kinesin, dynein
two proteins that attach to vesicles or organelles and walk on microtubules, transporting their cargos where needed
centrosome
a structure in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division. has 2 centrioles
centrioles
near the nucleus in animal cells, occurring in pairs and involved in the development of spindle fibers in cell division. each is composedof 9 triplets of microtubule
basal bodies
centrioles that have migrated near the cytoplasmic membrane
triplet
one complete microtubule and two partial microtubules
dyenin arms
slide the doublets past each other, creating movement
doublet
one full microtubule and one partial microtubule
9+2 construction
9 doublets in the periphery and 2 complete mictoubules in the centre
coccus
a spherical bacterium
rod
a rod-shaped bacterium
spirillum
a bent-rod bacterium
spirochete
a spiral-shaped bacterium. STDs
bacterial cell wall
allows bacteria to withstand the intracellular osmotic pressure. responsible for shape and rigidity
purple
colour of Gram+ bacteria after staining
pink
colour of Gram- bacteria after staining
safranin
counterstain in Gram's stain
thick
layer of peptidoglycan in Gram+ bacteria
thin
layer of peptidoglycan in Gram- bacteria
NAG, NAM
the two sugars in peptidoglycan
D-amino acids
amino acids with the NH3+ group on the right in short peptide side chains of peptidoglycan
link between NAM and NAG
the target of lysosome in peptidoglycan of bacteria
interbridge cross-linking
the cross-linking of two peptidoglycan in Gram+ bacteria
sugar backbone polymerisation
provides rigidity to the structure in only one direction
direct cross-linking
the cross-linking of two peptidoglycan in Gram- bacteria
transpeptidation
the process of cross-linking to a peptide side chain
TA, LTA
composed of glycerol-P (3C) or ribitol-P (5C). decorated with amino acids and sugars. covalently bonded to peptidoglycan
sortase
an enzyme that covalently attaches wall-associated proteins to peptidoglycan
negative
charges of teichoic acid and lipoteichoic aicd
periplasm
the space between the outer membrane and the cytoplasmic membrane in Gram- bacteria. location of peptidoglycan
lipolysaccharides
embedded in the outer membrane of gram negative bacteria. provides structural integrity and protection from chemical attacks
lipid A
a lipid moiety toxic to many animals. an endotoxin that plays a major role in pathogenesis of Gram- bacterial pathogens. attaches to LPS
o-specific polysaccharide
consists of repeating sequences of 2,4 monosaccharides. used to identify different strains of one species of bacteria. huge diversity
archaeal cell wall
peptidoglycan absent. usually no outer membrane. diverse. may contain proteins
pseudopeptidoglycan
component of archaea cell walls. similar to peptidoglycan in morphology but contains different sugars. lacks D-amino acids
heteropolysaccharides
repeating units of 2+ sugars in some archaeal cell walls
S-layers
crystalline appearance of cell walls when viewed by electron microscopy. in archaea and some bacteria
capsule
a layer synthesised by archaea and bacteria composed of polysaccharides or proteins. covalently bonded to outer membrane or peptidoglycan layer. protects against host defense system
flagella
surface appendage used for locomotion. 15-20 µm long
monotrichous
single flagellum
petritrichous
many flagella all around cell surface
lophotrichous
many flagella, originating from one end of the cell
L, P, MS, C
rings in Gram-
P, MS, C
rings in Gram+
mot protein
a protein that uses the proton motive force to power the movement of the flagellum
MS/C ring, Mot proteins, rod, P ring, L ring, hook, cap, filament
flagellum synthesis from first last
taxis
directed movement toward or away from a gradient of chemical or physical agents
chemotaxis
chemicals, nutrients, antibiotics, etc.
phototaxis
light (phototrophic organisms)
aerotaxis
oxygen
osmotaxis
ionic strength (high/low salt concentration)
fimbriae
attach microorganisms to surfaces. form rigid, rod-like structures. primarily on Gram- bacteria
chaperone
a protein that assists in fimbriae assembly by binding to a fimbriae subunit and bring it to the surface
usher
a protein that assist in fimbriae assembly by forms a pore in the membrane to push subunits out of the membrane
surface adhesins
carry out adhesion to surfaces in Gram+. only one protein. mediate very close attachment
sortases
assembles fimbriae of Gram+
Gram+
anchored in peptidoglycan. pilin proteins. covalently-linked to one another. assembled enzymatically by sortases
Gram-
anchored in outer membrane. pilin proteins. strand exchange. no covalent bonding. accessory proteins needed
endospores
highly differentiated cells that are extremely resistant to harsh environmental conditions
exosporium
a layer around the cell made of proteins
spore coat
a layer around the cell made of spore-specific proteins (keratin-like)
cortex
a very thick layer of peptidoglycan around the cell
core
contains the genome of the cell and proteins useful for germination
DPA, Ca2+
bind water and dehydrate the core
SASPs
bind to DNA in the genome and help protect it against UV light damage
asymmetric cell division
first stage of endospore formation. commitment to sporulation. prespore forms
engulfment
second stage of endospore formation
cortex formation
third stage of endospore formation
spore coat forms
fourth stage of endospore formation
maturation, cell lysis
fifth stage of endospore formation
germination
last stage of endospore formation