Ch 2: Microbial Cell Structure & Function Flashcards
3 usual cell shapes in microbes
- coccus
- rod
- spirillum
3 unusual cell shapes in microbes
- spirochete
- budding and appendaged bacteria
- filamentous bacteria
what are characteristic arrangements in cells
cells remain in groups and clusters even after cell division in characteristic arrangement that can assist in identification
different ways of cell arrangement examples
- cocci in chains
- cocci in clusters
- rods in chains
what is morphology
genetically encoded property that maximizes fitness in a particular habitat
how can morphology maximize fitness
- optimization of nutrient uptake
- swimming motility in viscous environments of near surfaces
- gliding motility (like filamentous bacteria
Can the morphology predict physiology, ecology or phylogeny of a cell
typically, no
what is the size range for prokaryotes
~0.2um – 700 um in diameter
size of the average rod in bacteria
2 um
what is the size of most eukaryotes
8 um or larger
examples of very large prokaryotes
- Epulopiscium fishelsoni (bigger than 600 um)
- thiomargarita namibeinsis (400-750 um)
how does thiomargarita magnifica survive
by oxidixing sulfur. They are thread like creatures that are 50 times bigger than any other known bacteria
Small cells have more _______ relative to cell volume than large cell
surface area
core difference between small and large cell
the high surface are to volume ratio
what are the benefits of a large surface area
- support greater nutrient exchange
- grow faster than large cells
Limited resources can work out for small cells or large cells
small. a large population of small cells can be taken care of, compared to large population of large cells
What are the benefits of having more cell division, which is easier in small cells
more cell divisions = more mutations = faster evolution
In cells that really small, what should the volume of a cell consist of
proteins, nucleic acids, ribosomes etc - so it may get difficult
what cell size are needed on a minimum
0.15 um is marginal. 0.1 is insufficient
usually cell size in open oceans
0.2 - 0.4 um in diameter
what is the size of pathogenic bacteria
very small.
If pathogenic bacteria are small, how do they accommodate all cell functions
their genomes are streamlined with some gene functions provided by hosts
what is the cytoplasmic membrane
a thin structure that surrounds the cytoplasm and separates it from the environment
what does the cytoplasmic membrane do
regulates traffic of substances into and out of the cell
what happens if the cytoplasmic membrane disrupts
cell dies
what holds all of the contents of the cell in one place
cytoplasmic membrane
what is selectively permeability
regulation of traffic of substances that go in and out of the cell
what is constitutes of the cytoplasmic membrane
composed of hydrophobic (fatty acid) and hydrophilic (glycerol phosphate) components
is fatty acid hydrophobic or hydrophilic
hydrophobic
is glycerol-phosphate hydrophilic or hydrophobic
hydrophilic
In what environment to phospholipids naturally form a bilayer
aqueous solution
how are the fatty acids organized in the bilayer
fatty acids point inwards and the hydrophilic portions remain exposed to the external of cytoplasm
what is the cytoplasmic membrane
semi-fluid phospholipid bilayer with embedded proteins
what are integral membrane proteins
they’re permanently embedded in the membrane.
what proteins span the membrane
transmembrane integral proteins
chemical structure of the lipid-anchored proteins
lipid molecule attached to an amino acid – which inserts into the membrane
What is the peripheral membrane
on the surface of the membrane, without inserting
in archaea how are hydrocarbons derived?
from isoprene
what is isoprene
5 carbon branched molecule
in archaea how are hydrocarbons attached to glycerol
by ether linkages
In bacteria eukarya, with links the hydrocarbon with glycerol
ester linkages
in bacteria archaea, how are hydrocarbons derived
fatty acids
3 membrane proteins
- integral membrane proteins
- lipid-anchored proteins
- peripheral
What are the 2 major types of archaeal lipids
- Glycerol diethers
- diglycerol tetraeither
Chemical structure of glycerol diethers
2 phytanyl groups attached to a glycerol
What is a phytanyl
20 carbon branched hydrocarbons, basically 4 isoprene units
what is a isoprene
5 carbon chain with double bonds
chemical structure of diglycerol tetraether
2 biphytanyl groups attached to a glycerol molecule at both ends
what is a biphytanyl molecule
20 carbon branched hydrocarbons
What does a diglycerol tetraether form instead of a lipid bilayer
lipid monolayer
what is the benefit of cyclic rings in hydrocarbon chains
increased rigidity
example of a archaea that has cyclic rings in its lipids
crenarchaeol
types of archaeal membranes
- lipid bilayer
- lipid monolayer
- combination of bilayer and monolayer
which type of archaeal lipid membrane is extremely resistant to heat
lipid monolayers
which type of archaeal lipid monolayer are widely there in hyperthermophilic archaea
lipid monolayer
what is hyperthemophilic
organisms that can live in extreme hot environments. they can grow best at more than 80 C
in permeable membranes what portion of the membrane is a tight barrier for difussion of substances
hydrophobic portion
can water pass through the phospholipid molecules
No its too small to pass
Why cant water pass through phospholipid membrane
water is a polar molecule (charged) and the head of the phospholipid molecule is non polar molecule (uncharged) . A polar molecule cannot diffuse/dissolve through a non polar molecule. Anything that can diffuse through the bilayer has to be similar to a non polar
How is water transported into the cell
through membrane proteins called aquaporins
What are the 3 transport mechanisms in prokaryotes (to and fro the phospholipid bilayer)
- simple transport
- group translocation
- abc transporter
what is simple transport in prokaryotes
passive diffusion of substances - without using energy - typically driven by the proton motive force (?)
what is group translocation in prokaryotes
when a subtance is diffused through the bilayer wile being chemically modified
What is ABC transporter in prokaryotes
they are membrane bound proteins that pump substances in and out of cells
What does ABC transportation need
- substrate protein
- membrane transporter
- ATP Hydrolyzing protein
What is the proton motive force
When there is an abundance of H+ (protons) on one side [of the cell] compared to the other side, there is force that is created, and they want to come to the other side where is a net negative charge - thats proton motive force
what is an ATP hydrolyzing protein
Hydrolyzing means breakdown. The hydrolyses of ATP powers cellular activities. The proteins that hydrolyze ATP are called ATP hydrolyzing proteins (like ATP Synthase)
2 main purposes of the cell wall
- protects against lysis (breaking of or disintegration)
- gives shape and rigidity to the cell
What is difference between gram-positive and gram-negative bacteria
differ in staining due to cell wall structure difference
What are gram-positive bacteria
thick cell wall. have thick layer of peptidoglycan (envelope around the cytoplasmic membrane aka the phospholipid bilayer) + inner cytoplasmic membrane
what are gram negative bacteria
thin cell wall. Thin layer of peptidoglycan + inner cytoplasmic membrane + outer membrane
when staining, what color are gram positive bacteria. what is the name of the stain
purple. A basic fuchsin stain is used.
when staining, what color are gram negative bacteria. what is the name of the stain
pink. basic fuchsin stain
do gram postive bacteria has an outer membrane
no
what is the chemical structure of peptidoglycan
repeating subunits of glycan tetrapeptide
What is there in a glycan tetrapeptide
- 2 Sugar derivatives
- amino acids
What are the 2 sugar derivatives in glycan tetrapeptide
- N-acetlyglucosamine
- N-acetlymuramic acid
what amino acids are there in glycan tetrapeptide
- L-Alanine
- D-Alanine
- D-Glutamic Acid
- L-lysine OR a lysine derivative (like, Diaminopimelic acid)
what enzyme can weaken the cell wall
lysozyme
Examples of where lysozyme is present
- Tears
- saliva
- other bodily fluids
what do B-1,4-glycosidic bonds connect
sugars in a long chain
what do peptide bonds connect
one glycan chain to another
What is main feature of glycosidic bonds
create rigidity and strength in one direction (X)
What is the main feature of peptide bonds
give strength in other direction (Y)
How do glycosidic and peptide bonds work together
work together in peptidoglycan. Imagine an axis, peptide bonds work in Y direction and glycosidic bonds work in X direction
in gram negative bacteria, where do peptide bonds occur
between DAP of one chain and D-Alanine of another chain
In gram positive bacteria, how are connections formed
through a short string of peptides, an interbridge, whose form varies from species to species
what is a glycine residue
unique amino acid chain where all side chains are hydrogen atoms
gram positive cell walls contain up to _____ % of peptidoglycan
90
what are the “cables” in gram positive cell walls
“cables” are basically cross linked glycan strands, about 50 nm wide and the these cables itself can cross link to form an even stronger structure
What are teichoic acids
polymers in gram positive bacteria. They help to regulate cell morphology and cell divisions
are teichoic acids found in gram positive or negative acids
only in gram positive bacteria
what is the chemical structure of techoic acids
polymers of glycerol or ribitol joined by phosphate groups
to what are techoic acids connected in gram positive bacteria
to the peptidoglycan or plasma membrane lipids
are teichoic acids positively or negatively charged
negatively. bacterial cell walls are also negatively charged. and teichoic acids is in the bacterial cell wall
In gram - negative bacteria what is the outer membrane
it is a lipid bilayer
in gram negative bacteria, what is the composition of the inner membrane
thin peptidoglycan layer
what does the outer membrane in gram negative bacteria contain
- phospholipids
- lipopolysaccharides or LPS
How abundant is LPS (lipopolysaccharide) in the outer membrane
it covers most of the phospholipids in the outer half of the outer membrane
what connects the peptidoglycan layer (inner membrane) to the outer membrane
lipoproteins `
What does the structure of LPS consist of
- Lipid A
- Core Polysaccharide
- O-Specific polysaccharide
what is the chemical structure of lipid A in LPS
Disaccharide of glucosamine phosphate linked to fatty acids through amine groups
what is the periplasm
region between two membranes
What happens in the periplasm
very high conc of proteins:
1. hydrolytic enzymes, these degrade food molecules
2. binding protiens, used for transport
3. chemoreceptors, which aid cell movement
what is porins
Proteins that function as channels for entrance and exit of solutes
why is the outer membrane relatively permeable to small molecules
due to the presence of porins
Which bacteria (negative / positive) cells are nearly invisible until stained with 2nd dye
gram negative
What happens to the CV-Iodine complex in gram positive and negative cells during the staining process
gram-negative cells: alcohol goes into the cells and extract CV-Iodine, leaving it colorless
gram-positive cells: alcohol dehydrates, causing pores to close and trapping the CV-Iodine complex, leaving it purple
can most prokaryotes live without a cell wall
no
Examples of prokaryotes that naturally lack cell walls
- Thermoplasma and its relatives
- Mycoplasma
How do prokaryotes without cell wall survive
- have tough cell membranes
- Or live in strict osmotic regulated environment
What does it mean to have a osmotic regulated environment
it is a homeostatic mechanism that regulates the optimum temperature of water and salts in the tissues and body fluids
Do archaea cell walls contain peptidoglycan `
no
do archaea contain an outer membrane
no
What kind of cell walls do archaea have
pseudomurein cell walls
What are pseudomurein cell walls
- similar to peptidoglycan
- contains N-acetylglucosamine linked to N-acetylalosaminuronic acid
some archaea that live in _______ environment have polysaccharide walls
high salt
The cell walls of archaea that live in high salt environments have a high amount of —-
They’re highly sulfated. SO4^2-
what is the most common type of cell wall in archaea
S-Layer
Are S-layer cell walls found in bacteria
in some bacteria, yes
How is the S-Layer formed
interlocking layers of:
- Protein/Glycoprotien
That form a paracrystalline structure
What does S-Layer do
- protects from osmotic lysis
- Acts as a selective sieve
- retains proteins near surface
What is the S - Layer present with (sometimes?
Polysaccaride-based layer
what are cell inclusions
granules, crystals or globules of a substance in the cytoplasm, usually partitioned off from the rest of the cell
What can cell inclusions be used for
used as store substances when in excess for later use
What are some examples of substances that can be stored in cell inclusions
- Carbon
- Inorganic Phosphate
- Sulfur
where are gas vesicles present?
in many planktonic prokaryotes
What are gas vesicles made of
protein
What are gas vesicles shaped like
Spindle-shaped
What are gas vesicles permeable to
gases
what are gas vesicles impermeable to
water
Advantages of gas vesicles
- Increases buoyancy
- Allow cells to adjust vertical position in a water column
what are slime layers
sticky or slimy materials on cell surface that have secreted polysaccaride or protein
what is the structure of bacterial capsules?
consist of tight matrix that adheres firmly to the cell wall
how are slime layers attached to the cell surface
loosely attached, so they can be lost from the cell surface
what is the function of capsules and slime layers
- Help in attachment
- protect immune invasion
- protect from dehydration
difference between fimbriae and pilli
Fimbriae are bristle-like short fibers occurring on the bacterial surface, Pili are long hair-like tubular microfibers found on the surface of bacteria.
What are fimbriae and pilli
filamentous proteins extending from surface of cell
What is the function of fimbriae
helps enable cells to stick to surfaces
What are the functions of pilli
- facilitate genetic exchange by conjugation
- adhesion to specific host tissues
- twitching motility
what is flagella
Threadlike locomotor appendages extending outward from the plasma membrane and cell wall
What is the function of flagella
Swimming and motility
what are the 4 different forms of flagella arrangements
- Polar
- Lophotrichous
- Amphitrichous
- Peritrichous
What is the polar arangement of flagella
Flagella attached at one or both ends
What is the lophotrichous arrangement of flagella
A tuft (group) of flagella at one end
What is the amphitrichous arrangement of flagella
Tufts at both ends
what is the peritrichous arrangement of flagella
Many locations around the cell
What are the 3 main components of flagella
- Basal Body
- Hook
- Filament
What is the basal body in flagella
The base & “motor” of the flagella
what is the function of the basal body in flagella
Anchors the flagella in cytoplasmic membrane & cell wall
What is the hook in flagella
links basal body and filament
What is the filament in flagella
Extends from the cell surface to the tip
What is the structure of the filament in flagella
- Composed of a hollow rigid cylinder of flagellin protein
- Helical
How does the basal body move the flagella
rotates the flagella much like the propeller on a boat motor
what powers the rotation done by the basal body in flagella
protons, through Mot proteins
How is the flagella in archaea used
power swimming motility
Compared to bacterial flagella, what is the size of the archaea flagella
its thinner in diameter
How does a thin diameter affect swimming on archaea
slower swimming
what are archaea flagella made of
different flagellin proteins, similar to bacteria flagellin
what powers the swimming done by flagellla in archaea
ATP. and not proton motive force
Did flagellar motility evolve together for bacteria and archaea
no, they evolved separately
Flagella rotational speed is related to ______
strength of the proton motive force
Why do different archaea species have different swimming maximum speeds
because swimming speed is genetic, hence different for each species
How does different flagella arrangements, affect swimming
the swimming motions differ with flagella arrangement
What type of flagellated cells move slowly in a straight line
peritrichously flagellated cells
What type of flagellated cells move more rapidly, spinning around and dashing from place to place
polarly flagellated cells
