Lecture #2 - Cell Structure & Function PART 2 Flashcards
Peptidoglycan make up…
bulk but not all cell wall structure
Species of _____ separated into two groups based on Gram stain
Bacteria
Gram +
- still has a (-) cell surface
- THICK peptidoglycan
Gram -
- has net (-) charge
- THIN peptidoglycan
Some bacteria are exceptions being neither Gram + or Gram -
Mycoplasma
Gram-positives and gram-negatives have different cell wall structure
• Gram-negative cell wall
- Two layers: LPS (lipopolysaccharide) and peptidoglycan (THIN)
• Gram-positive cell wall
- One layer: peptidoglycan (THICK)
Cytoplasmic membrane
NOT a component of the cell wall
- just the boundary that forms around cytoplasmic content
- for all living cells
Peptidoglycan
RIGID layer that provides strength to cell wall
- organism can handle itself under extreme conditions since it’s just 1 cell
Describe difference b/t human cells and bacteria cells (in terms of cell wall)
- humans have NO cell wall, just have a plasma membrane (have lots of cells)
- BUT bacteria cells are unicellular, therefore anything that happens to that 1 cell will be the end of the cell structure
- so using peptidoglycan it has this peptidoglycan so it can better handle these situations/withstand so it’s not dying easily
Polysaccharide
peptidoglycan is formed by polysaccharide which is a complex sugar structure
Polysaccharide composed of:
- N-acetyl glucosamine (NAG) and N-acetylmuramic (NAM) acid
- Amino acids
- Lysine or diaminopimelic acid (DAP)
- Cross-linked differently in gram-negative bacteria and gram-positive bacteria
- Form glycan tetrapeptide
The Polysaccharide is…
crosslinks made out of amino acids
- link top to bottom, in order to make the structure of the peptidoglycan chain nice & strong
The L & D on the polysaccharide is…
indicative of the stoichiometry
- uses a D form of an AA that we don’t see in our cell
NAG-NAM-NAG-NAM-NAG-NAM-etc.
disaccharide is the first 2 pieces
- polymerizes again & again to create a chain around the cell
- comprises peptidoglycan layer
The AA chain only comes out of the…
NAM
Crosslinks in the peptidoglycan…
makes lattice structure strong, so if you apply a horizontal force of any kind, it will to an extent be able to withstand that
What would you prefer if given the option on the arrangement of the polysaccharide?
LEFT one –> requires less GTP
- b/c attaching AA’s by peptide bonds is a massive GTP requiring process (v. expensive) & you also need all the Gly residues
- *total for right one will need 5 additional gly residues & have to form additional 5 peptide bonds (so more energy)
What does penicillin target?
the enzyme used to form the polysaccharide
If you’re taking penicillin to target an infection, what part of the cell structure will NOT be okay? Chains or crosslinks that reinforce structure?
CROSSLINKS
If you look at a micrograph of bacterium that’s trying to grow in the presence of penicillin, you literally see holes blown on the side of the bacterium. Why would this organism have holes blown on the side as a result of having this cross link inhibition that penicillin provides?
NO STRENGTH
- & water wants to move in
- when that happens, the organism will have no protection b/c the crosslinks are being inhibited
Penicillin is useful against gram + organisms NOT against gram -? Why?
- more peptidoglycan –> more crosslink
- more repercussion for that type of organism
- b/c gram - some only have 1 PD layer so penicillin is essentially useless
Describe the structure of peptidoglycan
- NAG & NAM
- N-Acetyl group - acetyl group linked with a N to C2 of the sugar (true for NAM & NAG)
- Peptide cross-links - perpendicular
- B(1,4)
- Lysozyme-sensitive bond
- Glycan tetrapeptide - 4 AA’s attached to a sugar
Lysozyme-sensitive bond
incorporate it in sweat, saliva, & tears
- destroys NAM/NAG linkages specifically b/t NAM & NAG
- when it breaks that bond, the linear chains are fragmented (disassembling the cell wall of the organism)
- in doing so it protects our eyes, skin, mouth against bacterial infection
- but has to have peptidoglycan & will have more of an impact on organisms that are gram + b/c they have thick layers of PD
More than 100 different PG/PD structures identified…
- have same core PD/PG arrangement & crosslinks provided that they have more than 1 layer but way they form this will be diff. depending on the species
Vary in peptide cross-links and/or interbridge
No ______ is present in gram-negative Bacteria (e.g. E. coli). Why?
INTERBRIDGE
- b/c can have 1 single layer of PD (therefore, nothing to crosslink to)
The interbridge in Staphylococcus aureus (gram positive) is made up of…
5 glycine residues
Gram - have…
- NO interbridge
- can have crosslinks - but if it’s just 1 layer than not
- THIN PD
- if more than 1 layer of PD it wouldn’t have interbridge but still crosslinks
Glycosidic bonds b/t…
NAM & NAG
Peptide bonds…
AA’s used to form chains
Gram-positive cell walls
• Contain up to 90% peptidoglycan –> very THICK
- forms a helic (3D)
• Common to have TEICHOIC acids
- LIPOTEICHOIC ACIDS
Teichoic acids
(acidic substances) embedded in their cell wall
- common in gram + cell walls
- like toothpick that puncture bread (PM) underneath
Lipoteichoic acids
teichoic acids covalently bound to membrane lipids
- toothpick penetrates through bread too (PM) underneath
Teichoic acids & Lipoteichoic acids…
DO NOT exist in gram - organisms which have LESS PD
Gram + only (i.e. may not be present, but if is will be in gram +)
1) Lipoteicholic acids
2) Endospores
3) Interbridges
Model of Peptidoglycan Surrounding the Cell
- Backbone formed of NAM and NAG connected by GLYCOSIDIC BONDS
- Crosslinks formed by PEPTIDES
• Peptidoglycan strand is HELICAL
- Allows 3-DIMENSIONAL CROSSLINKING
- E. coli has 1 layer
- Some cell walls can be 50 - 100 layers thick, e.g. BACILLUS SPECIES
Peptidoglycan strand is helical, allows…
Allows 3-dimensional crosslinking
E. coli has ___ layer
1
Some cell walls can be ____ layers thick, e.g. _______
50-100
Bacillus species
Bacillus species
- cell walls is 50 - 100 layers thick
- gram +
- purple
- they form endospore structures (indicator of gram +)
Prokaryotes that lack cell walls
Mycoplasmas
Mycoplasmas
• Prokaryotes that LACK cell walls (comparable to animal cell)
- v. small
- Group of pathogenic bacteria
- Have sterols in cytoplasmic membrane–adds strength and rigidity to membrane
Mycoplasmas have sterols in cytoplasmic membrane…
– adds strength and rigidity to membrane
sterols - cholesterol/other sterols which adds hot/cold stability (we also use cholesterol)
- better able to withstand temp flex’s
- usually a eukaryotic thing
Thermoplasma
- Prokaryotes that lack cell walls
- Species of Archaea (would never have peptidoglycan anyway - no cell wall here!)
- Contain LIPOGLYCANS in membrane that have strengthening effect
Gram negatives cell wall…
- total cell wall contains ~10% peptidoglycan (THIN)
* Most of cell wall composed of outer membrane, aka lipopolysaccharide (LPS) layer (still a bilayer)
Most of GRAM - cell wall composed of outer membrane, aka lipopolysaccharide (LPS) layer
- LPS consists of CORE POLYSACCHARIDE and O-POLYSACCHARIDE
- LPS replaces most of phospholipids in outer half of outer membrane
- ENDOTOXIN (lipidA): the toxic component of LPS
Endotoxin
toxic when RELEASED from dead cell (not toxic when attached)
Endotoxin (lipid A) is only in…
gram -
What does the outer leaflet of the outer membrane consist of?
- o-specific polysaccharide
- core polysaccharide
- Endotoxin (lipid A)
(LPS & phospholipids basically)
Gram (-) sepsis
- organism that’s everywhere growing & multiplying
- endotoxin dramatically activates the immune system b/c it’s gram -
- immune system does freak out & causes blood vessels to dilate (inflammation - okay in foot or throat b/c increases flow when you dilate a blood vessel & allows delivery of O2 & nutrients & immune cells for healing, immune responses to clear things out)
- BUT when its sestemic (sepsis), that inflammatory response causes all of arterial to vasodilate
Why might this be a problem (gram - sepsis) if all BV’s are dilating not just ones located in an infected tissue?
- BP drops dramatically LOW –> DON’T have enough pressure to force fluid to your tissues to deliver O2 & nutrients
- tissues start to die
- amputation b/c wasn’t enough pressure to feed the tissues
(like frost bite - vasoconstriction)
Why should you NEVER give an antibiotic that aggressively kills bacteria if you have sepsis?
b/c ENDOTOXIN gets RELEASED when you aggressively kill bacteria in really high [ ] in the cell structure
- can kill them
What should you use instead for gram - sepsis?
would want to use a BACTERIOSTATIC drug - keeps everything constant
- should be used to treat gram - sepsis b/c it interfers with growth
- prevent them from increasing # & immune system goes & cleans up the organisms that we’re there
- drug doesn’t do killing & need to have a functional immune system to do the destruction
Porins in the LPS/the outer membrane are…
NON-SPECIFC
- just providing a channel for polar material that’s size appro.
Things like ABC transport, group translocation etc. in the LPS/the outer membrane are…
HIGHLY specific
- allow organisms to enter through
Bacteriostatic drug should be used to treat…
gram - sepsis
Cytoplasmic membrane
highly specific with transmem. proteins that select for CERTAIN nutrients or ions to be able to enter the cell
LPS: The Outer Membrane
Periplasm:
space located between cytoplasmic and outer membranes
• ~15 nm wide
• Contents have gel-like consistency –> VISCOUS (lots of nutrients)
• Houses many proteins
ex: periplasmic binding proteins
- bring nutrients to the ABC transporters
think: yard
- just came through fence & is able to wonder around & if you meet specificity of the periplasmic proteins you can enter house (cytoplasmic envir. of cell)
Ex of proteins in the periplasm
ex) periplasmic binding proteins
- bring nutrients to the ABC transporters
LPS: The Outer Membrane
Porins:
channels for movement of hydrophilic low-molecular-weight
substances
- have Beta pleated sheets (unique secondary structure)
- non-specific entry
- water-soluble & hydrophilic, but small enough to meet size of the pore
- therefore, doesn’t serve as permeability barrier
LPS: The Outer Membrane
Porins:
channels for movement of hydrophilic low-molecular-weight
substances
- non-specific entry
- water-soluble & hydrophilic, but small enough to meet size of the pore
- therefore, doesn’t serve as permeability barrier
Porins have…
Beta pleated sheet (unique secondary structure)
Relationship of Cell Wall Structure to Gram stain
• In Gram stain reaction, insoluble crystal violet-iodine (CV-I) complex forms inside cell
- crystal violet sticks to (-) charge of cell
- iodine bulkens/increases structural size of the dye
• Complex is extracted by alcohol (decolourizing step) from gram-negative, not gram- positive bacteria
Reason:
• Gram-positive bacteria have thick cell walls consisting mainly of peptidoglycan
- Becomes dehydrated during alcohol step so pores in wall close
- Prevents CV-I complex from escaping –> cell remains purple
• Gram-negative bacteria – alcohol penetrates OM
- CV-I extracted from cell
- Cells appear nearly invisible (colourless) until counterstained with second dye (safarin - basic pink dye, stick to everything (-) charged (including gram +’s) but purple overpowers them)
- but now includes gram -‘s that were colourless, turning them pink
Archaeal Cell Walls
- NO peptidoglycan (prokaryotes)
- Typically NO outer membrane
- Pseudomurein
- Cell walls of some Archaea LACK pseudomurein
- S-Layers
Prokaryotes NEVER have…
peptidoglycan
Pseudomurein
Archeal don’t have PD but still have a cell wall:
• Polysaccharide similar to peptidoglycan
- not common among all archaea but some have it
• Composed of N-acetylglucosamine (NAG) and N-acetyltalosaminuronic acid (NAT) (REPLACES NAM of PD)
• Found in cell walls of certain methanogenic Archaea
- makes CH4 (methane)
Pseudomurein structure
- NAG & N-Acetyl-talosaminuronic Acid
- Lysozyme-INsensitive B (1,3)
- Peptide cross-links (b/t NAG & T for these - PD was b/t NAM residues M—M)
Describe B (1,3) lysozyme-INsensitive in Pseudomurein
NOT B (1,4), therefore WON’T work as a lysozyme substrate
- therefore, a lysozyme that we have in our sweat, saliva & tears WOULDN’T be effective agains the pseudomurein cell wall b/c it doesn’t have the B (1,4) linkage present b/t the NAM & NAG that was discussed for PD
- a lysozyme b/c it’s an enzyme & highly specific, WOULDN’T be able to cleave this & wouldn’t have effectiveness against the cell wall structure
B/c of the B (1,4) linkage, if archaea ever became pathogenic (b/c it can happen in future)…
our own defences in our sweat, saliva & tears WOULDN’T be effective in order to disturb the cell wall so we would have to rely on other means
Archaeal Cell Walls
S-Layers
• Most COMMON cell wall type among Archaea
- numerically dominants the pseudomurein
• Consist of protein or glycoprotein (protein that has sugar groups attached to the structure in order to create an alternative function)
• Paracrystalline structure
- crystallized structure –> ordered, firm
- SOME Archaea have ONLY S-layer (no other cell wall components)
- MOST have ADDITIONAL cell wall elements
Summary of Archaeal Cell Walls
- Variety of structures possible (diversity)
- SOME (pseudomurein) closely resemble peptidoglycan
• Others LACK polysaccharide (long chain of sugar - NOT just sugar units that are strategically placed onto a protein) completely
ex) S layer (protein or glycoprotein)
• Most Archaea contain some type of cell wall structure –
functions to prevent osmotic lysis and give shape (coccus, bacillus, etc.)
- EXCEPTION: thermoplasma spp. - archaea that has no cell structure
• Because they lack peptidoglycan, Archaea are resistant to lysozyme and penicillin
i.e. can’t use penicllin to target
How do Archaeal cell wall vary?
- pseudomurein, S-layer, add. components that could be added etc.
- compared to PD which is consist for almost all bacteria
Which Archaeal cell walls lack polysaccharide completely?
ex) S layer (protein or glycoprotein)
What is an exception to, “Most Archaea contain some type of cell wall structure?”
exception: thermoplasma spp. - Archaea that has NO cell structure
Because they lack peptidoglycan, Archaea are resistant to lysozyme and penicillin (explain)
i.e. can’t use penicillin to target
penicillin is not an effective chose B/C it TARGETS PD in partic., if you did gain an archeal infection when that would become pathogenic 1 day
- b/c it doesn’t have PD & PD crosslinks are specifically gonna be targeted by the penicillin drug
- therefore, can’t use penicillin to treat an archeal infection ever, b/c the target for that drug isn’t present in the archeal cell wall structure or in the archeal cell wall at all
- so you would need to use a protein syn. inhibitor for ex.
Cytoplasm
material bounded by plasma membrane (PM)
=CYTOSOL (FLUID) & ALL COMPONENTS WITHIN
EX) RIBOSOMES
Protoplast
PM + CYTOPLASM and everything within
• Macromolecules – amino acids, nucleotides, etc
• Soluble proteins ex) enzymes for glycolysis - allow metabolic pathways to happen with ease & simply b/c the enzymes can shift & find substrate & move things around
• DNA and RNA (nucleoid)
- RNA: transcripts produced for protein synthesis i.e. make a protein from a transcript thats come out
Proteins
• Serve many functions:
• Enzymes – Catalyze chemical reactions (rapid & efficient)
• Transport proteins – Move other molecules across membranes (that’s polar & of a partic. characteristic)
ex) porins, ABC transporters etc.
- Structural proteins – Help determine shape of the cell (morphological det)
- Involved in cell division
• Proteins are made of polypeptides
- think: hemoglobin - come together properly for function
• Polypeptide – a long polymer of amino acids joined by peptide bonds
Proks can have a cytoskeleton…
made out of protein (proteination - made out of protein, plays role in determining shape or morphology of cell), the same way euk’s have a cytoskeleton
Describe the peptide bonds of proteins
- partial double bond characteristics
- restricts rotation (shorter)
- plays role in determining shape that proteins can assume
The Nucleoid
• Region that contains the genome
- NOT a fenced off area but good chance you’ll find a chromosome there
- DNA
- Carries genetic info of all living cells
- Polymer of deoxyribonucleotides
The Nucleoid
The typical bacterial genome:
Single circular double stranded (ds) DNA chromosome (ALWAYS carries the genetic info in DNA b/c it’s a LIVING cell (prok, animal or plant cell)
MAY have one or more plasmids
• Smaller circular dsDNA
The typical bacterial genome, MAY have one or more plasmids:
- Smaller circular dsDNA
- Self-replicating –> autonomously!
- can photocopy themselves when rest of cell & chromosome are not duplicating & div.
- these bad bacteria hand out these copies v. generously to other bacteria & pass it along to another (to make someone sick) –> v. generous & like to share
- how antibiotics resis. is able to spread throughout community
• Carry non-essential genes
- BUT if an organism finds itself in a partic. envir. or under a partic. set of conditions, it’s def gonna BENEFIT from having them
- Selective advantage –> allow cell to produce a toxin or enzyme or a gene for penicillin resistance to allow a cell to survive presence of penicillin b/c it gives it the phenotype of resistance to that partic. drug
- if there, it will benefit from it - like ripping recipes that we don’t use
- Ex) Genes for antibiotic resistance
Genome =
TOTAL content of DNA in the cell!
If the plasmid was in the cell, would it be included in the genome?
YES
Is it guaranteed that the plasmid would be included in the cell tomorrow? Or can cell kick it out if don’t need?
NO it’s not guaranteed - it can come & go
- cells are v. genetically plastic (pick up/get rid of/moving around cellular comp. constantly)
What does the Genome include?
ESSENTIAL GENES
including: enzymes for glycolysis, ETC protein, transport proteins in mem. for ex
cell CANNOT live without - foundational for life & survival
What does the Plasmid include?
NON-ESSENTIAL GENES
- don’t need them - not necessary for energy production transporting nutrients in cell, but if cell has these plasmids it provides some kind of a selective advantage
Ribosomes in prok
Site of protein synthesis
70S ribosome (SMALLER than 80S euk)
• 2 parts
- 30S subunit (Small subunit) SSU
- Protein
- 16S rRNA - 50S subunit (large subunit) LSU
- Protein
- 23S and 5S rRNA
Cytoplasmic ribosomes
• Cytoplasmic proteins
PM associated ribosomes
• Membrane proteins
• Proteins to be exported from the cell
70S prok ribosome is _______ than 80S euk
SMALLER
What does the 16S, 23S or 5S rRNA mean?
how many nucleotides will comprise the piece
What ribosomes can a prok. ribosome have?
70S (50S + 30S)
& also could have 70S bound to PM - NOT all prok’s have but if there, they make protein that get exported (like rough ER) to outside of cell - could be toxin, signalling molecule that communicate with buddies nearby etc.
What are 2 differences b/t 23 rRNA & 16S rRNA?
1) 23 rRNA is LARGER - longer length
2) Nucleoid sequence is DIFF.
Ribosomes..
take a messenger rRNA piece & convert it to protein like a factory
- assembles AA’s forming peptide bonds by looking at what template is asking for in messenger rRNA, forming a polypeptide & then repeat
What ribosomes can a Euk cell have?
1) 80S ribosomes (40S + 60S)
2) Euks have 70S ribosomes too in mitochondria!
Do Euk’s have 70S CYTOPLASMIC ribos?
NO - b/c cytoplasmic ribo’s are 80S!
they do have 70S ribosomes but they are in the mitochondria!
Are Cell Surface Structures present on all bacteria or just some? Where are they?
Present on SOME bacteria
OUTSIDE of CELL WALL (1st thing you’ll see)
List the possible Cell Surface Structures that can be present on SOME bacteria:
- Capsules and slime layers
- Fimbriae
- Pili
List the Cell Surface Structures present on SOME bacteria:
- Capsules and slime layers
- Fimbriae
- Pili
What is the difference b/t Capsules and slime layers?
Capsules - VERY ORGANIZED
- & TIGHT to surface - provides a lot of contour dets to cell underneath
think: TIGHT sweatpants
- can see shape of person underneath
Slime layers - LOOSE
- think: BAGGY sweatpants
- still covering but DISORGANIZED & hanging off person - so you can’t see any of the shape dets underneath
Capsules and slime layers characteristics
BENEFICIAL
- Polysaccharide (sugar) / protein layers
- May be thick or thin, rigid OR flexible
What are 3 things that Capsules and slime layers do which are beneficial?
- Assist in ATTACHMENT to surfaces
- Protect AGAINST phagocytosis
- Resist DESICCATION
Describe how Capsules and slime layers, “Assist in attachment to surface.” By answering the q; what would happen after you come out of swimming pool of honey you jumped into?
- will be v. sticky!
- just like bacteria with capsule on outer layer - that sticks to things
- any bacteria that has a chance to stay inside your body must have some opp. to stick otherwise the organism won’t be able to last & will be ejected quickly
(cell surface structure that some bacteria have)
Describe how Capsules and slime layers, “Protect against phagocytosis” & what a phagocyte is
Phagocyte - immune cell used to bind to bacterium in order to get it to leave needs to have some kind of attachment spot
- if it doesn’t have that attachment site b/c its covered by a capsule for ex, it’s NOT gonna be able to be bound, taken in & destroyed - therefore, phagocytic process that our immune system uses is compromised b/c the organism has a capsule
Phagocyte
immune cell used to bind to bacterium in order to get it to leave needs to have some kind of attachment spot
Describe how Capsules and slime layers, “Resist desiccation”
organism is better able to keep water inside of the cell - rather than losing it to the envir., as a result of having this capsule layer on its outermost surface
If you have 2 bacteria that are genetically identical to 1 another (same genus, same species, same genetic comp.), but 1 has a capsule & the other does not. Which one are you worried about & why?
ENCAPSULATED BACTERIUM is what you’re worried about b/c it has the capacity to CAUSE DISEASE (contribute to virulent - ability of a bacterium to cause disease inside of the human body)
Other one isn’t a concern b/c it will just be flushed out or phagocytosis v. readily
Encapsulated bacterium…
has the capacity to CAUSE DISEASE
Fimbriae is typically a…
gram - feature
cell surface structure in some bacteria
Fimbriae
- also for adhersion
• Filamentous protein structures
- rather than a sticky layer (capsule)
• Enable organisms to stick to surfaces or form PELLICLES (like capsules)
- make contact with its surroundings
Pellicles
- formed by fimbraie
- like capsules
- layers (adhersion structures)
- can be everywhere or less numerous, therefore locations on outside of cell can be diff. depending on how bacterium choses to arrange them
Pilin protein
- indiv. circles
- is polymerized in order to create these pillicles
What can you think of fimbriae as?
think: sticking arms out on waterslide (fimbriae) so even though water is moving you out, having your hands adhered to your surfaces & immediate surroundings, you won’t get flushed away
Pili (pilus) features
- Filamentous protein structures (made out of same PILIN PROTEIN)
- Typically LONGER than fimbriae
What are 3 things that Pili do which are beneficial?
- Assist in surface ATTACHMENT
But mostly involved in the exchange (for sharing):
2. Facilitate genetic EXCHANGE between cells (CONJUGATION)
- Type IV pili involved in TWITCHING MOTILITY
Describe the Twitching motility that pili are involved in
gets shorter & taller - looks like a twitch
- point is that motility req’s attachment to the surface - the bacteria can’t just swim away
- pilus can DEpolymerize (release some pilus protein) so that it can be CLOSER to the surface, where it can FACILITATE more contact & can grab onto another receptor or you can exchange material etc.
Remember, PLASMIDS can…
replicate autonomously; by themselve, whether or not the rest of the cell is replicating
Describe the conjugation (genetic exchange b/t cells) due to pili
F+ cell (has fertility plasmid), contains F plasmid
- can use as a mode of exchange b/t members of the SAME or DIFF species (therefore diff. chromosomes)
- Replicates autonomously & copy goes through tunnel
- pilin protein polymerizes & creates a tunnel to an adjacent cell
- exchanging (conjugation) - F- (NO F plasmid) BECOMES F+ as a result of what happened with F plasmid
- so now this cell can do the same thing - grow a pilus & share genetic info with another organism present within the envir.
What is special about F- cell
NO F plasmid (but BECOMES F+ if conjugation with a F+ cell takes place)
- can’t form a pilus if F- initially
- b/c it didn’t have the gene to build the pilin protein & build the pilus
- so the other one (F+) forms it & sends some kind of material through, in order to change the phenotype - or what it has for the other organism
Conjugation (exchange that pili facilitate) doesn’t have to be…
F plasmid that’s passed - they can pass plasmids for antimicrobial resis, virulent factors like toxin, etc.
What is conjugation (exchange that pili facilitate) called?
MODE OF HORIZONTAL GENE TRANSFER
- b/c it’s not from mother cell to daughter cell - but it’s from buddy cells within the envir.
What to think of Cell Inclusion Bodies as
think: PANTRY - if you like spaghetti, you might have a lot of sauce in your pantry, you bought a lot on sale & store it so you have it in the long-term
produced by diff. species of bacteria - according to what it is that they like or what it is that they metabolize
- b/c at a given point in time (the same way you bought spaghetti sauce on sale), these organisms might find a lot of nutrients in their envir. that perhaps won’t be there at a certain point & time down the road
- so they decide to build this up so they have a lot of it, so in the later times when it may not be readily avail. they won’t be starving
Cell Inclusion Bodies
• Visible aggregates in cytoplasm
Come in diff. flavours:
- CARBON STORAGE POLYMERS
- Poly-β-hydroxybutyric acid (PHB): lipid
- Glycogen: glucose polymer - POLYPHOSPHATES: accumulations of inorganic phosphate PO42-
- SULFUR GLOBULES: composed of elemental sulfur - ENERGY
- cells need sulfur to be able to build cystein & methionine AA’s, which are imp. for protein syn. & have sulfur as apart of their R group identity - MAGNETOSOMES: magnetic storage inclusions
- gives cell magnetic property so it has opp. to align itself in a magnetic field (more back & forth according to that magnetic field depending on what it might need)
Cell Inclusion Bodies
Carbon storage polymers:
Can store:
• Poly-b-hydroxybutyrate (PHB)
- Lipid storage
• Glycogen granules
- Polymer of glucose
(carbon containing molecules could be catabolized to release energy!
- can take a glucose molecule or fat & see them in various locations in cell respir., to produce NADH & FADH2, which will be turned over to produce ATP in ETC
Cell Inclusion Bodies
Carbon storage polymers:
Poly-b-hydroxybutyrate (PHB)
• Lipid storage
gives opp…
to produce energy when you catabolize the molecule, but it also allows opp. to use it as carbon to build other structures (PL’s, glucose, AA’s etc.)
- anabolic material b/c C is so critical for all organic content of the cell
Cell Inclusion Bodies
Carbon storage polymers:
Glycogen granules
• Polymer of glucose
gives opp…
to hydrolyze in order to release free glucose which can be fed into cell respir. at the start of glycolysis & alternatively is a C building block that allows opp. to assemble other organic content
Why do we store glucose as glycogen in liver & muscles? What’s the reason we don’t store it as free glucose in our cells? Why do we bother to make a polysaccharide?
- glucose is osmotically ACTIVE, leaving free glucose lying around will create a HYPERTONIC that will serve to draw WATER IN - in order to avoid that, store it as glycogen!
- but glycogen is NOT osmotically active (doesn’t draw water in - good!)
think: leaving cash lying around will draw bad guys in but if stored it won’t have that affect
Cell Inclusion Bodies
Inorganic inclusions:
• Polyphosphate granules – VOLUNTIN (name given to granule that stores phosphate)
- Storage of phosphate and energy - used for energy b/c (-)ity of phosphate group causes it to affect energy production in beneficial ways
• Sulfur globules
- Storage of sulfur used in energy generation
What is PO42- used for inside a living cell?
1) ATP
2) Phospholipid structure
3) Nucleotides
Describe H2S –> S prime –> SO42-
H2S: FULLY REDUCED
- will give better energy yield
- can be OXIDIZED to release energy (same way glucose can be oxidized to release energy)
S prime: elemental
- PARTIALLY REDUCED
- can alsto be oxidized to release energy
SO42-: FULLY OXIDIZED (NO energy available)
- anaerobic respiration = terminal e- acceptor (would be the result of using sulphate as a sub)
Which of the 2 molecules, H2S or elemental sulfur, will have MORE energy if you catabolize them?
H2S - b/c it has MORE e’s
- will make more NADH, more FADH2 –> more ATP
Why might a cell be interested in SO42- if there’s NO energy avail?
can use SULPHATE as a substrate, if oxygen isn’t avail
- we use O2 to accept e’s in ETC during aerobic respir, but can use sulphate as a sub., for organisms (not humans b/c our energy demand is too high)
What might the energy yield look like if you compared O2 used versus sulphate used, when you talk about 1 molecule used when you catabolize?
LESS for SULPHATE - but still beats fermentation
- makes more energy than fermentation, but less energy than if you had used O2 as a terminal e- acceptor
SO42- has LESS of a + reduction potential - doesn’t want e-‘s as badly as O2 so its not as expulsive in e- transfer, meaning the energy yield is inevitably less
Cell Inclusion Bodies
Magnetosomes:
• Magnetic inclusions
- inclusion bodies with magnetic properties
• Intracellular granules of Fe3O4 or Fe3S4
- 2 magnetic particles that could be stored in the inclusion - giving the cell magnetic properties that allow it align itself in a magnetic field so that that organism orienting itself in that magnetic field can use that as a pathway for migration
Cell Inclusion Bodies
Magnetosomes:
Benefits/purpose:
• Gives the cell magnetic properties
- Allows it to orient itself in a magnetic field - can use that as a pathway for migration
- Bacteria migrate along Earth’s magnetic field – MAGNETOTAXIS
Magnetotaxis
- Bacteria migrate along Earth’s magnetic field
- riveals chemotaxin (moving in reference to a chemical) & phototaxis (moving in reference to light energy)
- can be displayed by organisms that specifically have these magnetic properties cause of the inclusion granules that contain magnetic molecules
Flagellum
ALLOWS MOTILITY
- can swim from 1 area to another (FREELY able to move)
- like drive car (go long distances)
Twitiching motility vs Flagellum
Twitching motility:
- twitching on the spot
- always in contact with surface & just adjusting proximity to the surface
Flagellum:
- can swim from 1 area to another (FREELY able to move)
- like drive car (go long distances)
Gas Vesicles
- CONFER BUOYANCY in planktonic cells
- Spindle-shaped, gas-filled structures made of protein
- Function by DECREASING cell DENSITY
- IMPERMEABLE to water
Describe purpose of Gas Vesicles in cyanobacteria for ex
- when you put something into a lake (with all interferences aside) it will sink when it drops into water
- but CYANOBACTERIA is PHOTOSYNTHETIC & the best exposure to sunlight is closer to the surface
- so they have a GAS VESICLE, which they INFLAT with gas which DECREASE there density so there tendency to want to sink is diminished & so it can hold its particular location within the water column & its impermeable to water
Why are Gas Vesicles in cyanobacteria impermeable to water?
b/c if that gas vesicle were to fill with water, it would just sink to the bottom (futile)
- want it to be impermeable to water, so when it fills with gas - it allows the organism to hold a particular spot within the water column - giving it ample access to sunlight which is a necessary material for photosynthesis
Describe Cyanobacteria form “blooms”
- using CO2 for C deems an organism autotrophic
- using sunlight deems an organism phototrophic
- b/c their photosynthetic - their having autonomous metabolism
- photoautotrophs
- perfect access to sunlight b/c of their gas vesicle
- plentiful supply of CO2 (b/c CO2 is a waste product from metabolism of all organisms that aren’t photosynthetic)
- things that would normally serve to limit growth, stop them from building new cells either
- *nitrogen & phosphorous - 2 things an organism will typically run out of, serving as a limiting factor
Describe Cyanobacteria form “blooms” in terms of Nitrogen or Phosphorous
*nitrogen & phosphorous - 2 things an organism will typically run out of, serving as a limiting factor
nitrogen - is used in fertilizer & as it rains comes it carries that water that now contains N, such that as run off it now goes into the lake
- N due to human activities (antropromorphic or anthropogenic activities) indicates that N is NOT LIMITING so then you turn to P since it is normally a limiting factor but in our landry detergent theres sometimes P so now that might be present in the runoff b/c of our waste (water supply will have components of our landry detergent that flushes away)
outcome: NOTHING limits cyanobacteria
- tons of sunlight, N, P, CO2 get them to GROW LOTS forming a BLOOM
- which are parasitic to all other organisms that are trying to live there b/c its so successful in taking over so much that all other organisms get choked out
- * also produce NEUROTOXINS - have toxic effects to fish & humans
- so we want to control this by controlling what we use in landry detergent & fertilizes to restore BALANCE
Endospores
GRAM + (species dependent - not all gram +’s)
bunkier that bacteria can put its genetic material inside, in order to ride out the store & when things become fav. it’ll then go back to a normal active state
Endospores benefits/functions:
- Highly differentiated cells RESISTENT to heat, harsh chemicals, and radiation
- DORMANT stage of bacterial life cycle
- nothing happening here with respect to metabolism
- NOT doing cell respiration, protein syn., DNA replication or anything relating to cell div. in spore form
- METABOLISM IS COMPLETELY INACTIVE
think: buying seeds at store (dormant), but if put in soil with an abundance of moisture it’ll germinate (in conditions it likes for success)
- but if not in those conditions, it choses to stay in its bunkier
- if you have apple seed a rabbit will eat it & then move away & deficate, so now you transferred that material to a new location where it can find success & also give fertilizer with the fecal matter (ideal for dispersal via wind, water, & animal gut - to help move it around to increase chances of bacterial success) - Ideal for dispersal via wind, water, or animal gut
Endospores benefits/functions:
- Highly differentiated cells RESISTENT to heat, harsh chemicals, and radiation
- DORMANT stage of bacterial life cycle
- nothing happening here with respect to metabolism
- NOT doing cell respiration, protein syn., DNA replication or anything relating to cell div. in spore form
- METABOLISM IS COMPLETELY INACTIVE
think: buying seeds at store (dormant), but if put in soil with an abundance of moisture it’ll germinate (in conditions it likes for success)
- but if not in those conditions, it choses to stay in its bunkier
- if you have apple seed a rabbit will eat it & then move away & deficate, so now you transferred that material to a new location where it can find success & also give fertilizer with the fecal matter (ideal for dispersal via wind, water, & animal gut - to help move it around to increase chances of bacterial success) - Ideal for dispersal via wind, water, or animal gut
- help move it around & increase success
Endospores produced only by…
some Gram positives
Ex) Bacillus sp. – aerobic Gram + rods (O2)
Clostridium sp. – anaerobic Gram + rods (no O2)
NO rule for O2 requirement –> independent on their state of O2 tolerance & utilization
Endospores
Vegetative cell:
Vegetative cell – capable of normal growth (when in vegetative state)
- doing protein syn, DNA replic, cell respir to produce ATP from ETC chain
• Metabolically active
Endospore
– dormant cell, formed inside of a mother cell (AKA vegetative cell)
• Metabolically INactive
• Triggered by LACK of nutrients
- b/c realize they won’t be able to survive this period of nutrient inability, so they come out in spore form & rid out the storm (until conditions become fav) to increase chances of success
• Takes about 8 - 10 hours
Mother cell (vegatative cell) ___ when spore is RELEASED
DIES
& mature spore comes OUT & waits until conditions are okay again
Endospores
Protective features of the endospore
- Layers
- Core
Endospores layers
• SPORE COAT and CORTEX – protect against chemicals, enzymes, physical damage, and heat
- hard shell-like structures that’ll provide protection against physical trama
- think: bullet proof vest - hard & protective, so delicate organs on inside won’t be subject to the harsh set of conditions
• TWO MEMBRANES – permeability barriers against chemicals
- b/c HYDROPHOBIC molecules are NOT freely able to pass
- unless theres a specific protein transporter/channel for those molecules
Endospores core
• DEHYDRATED – protects against heat
- b/c water does an excellent job of transferring heat to objects that its in contact with & this organism can be exposed to high temps
- want to get rid of water, otherwise those high temps can be transferred to DNA (delicate molecular structure that needs to be maintained if it’ll ever be vegetative again - instruction manual for life)
• Ca-DIPICOLINIC ACID and SASPs (chemicals to protect DNA)
- ioninc molecule with ionic bonds b/t Ca2+ & acid
• Protect against DNA damage
- if DNA is destroyed by high conditions of temp - it won’t be vegetative under fav. conditions
- organism protects it at all costs
Endospores can resist:
HARSH CONDITIONS
• Boiling for hours
• UV, g radiation
- SHORT wavelength means HIGH energy (damaging/dangerous)
• Chemical disinfectants
- meant to destroy things
- will be destructive, but the organism gets its protective shell with all the layers, so the chemicals can’t penetrate & cause any destruction
• Dessication
- b/c they have reduced water (dehydrated) & thick structure where water can’t escape & cause problems
• Age
- can grow old without experiencing (-) effects
Lifecycle of a spore forming bacterium STAGES
Stage I: Asymmetric cell division
• DNA replicates
• Identical chromosomes pulled to opposite ends of the cell
Stage II: Septation
• Divides cell into 2 unequal compartments:
• Forespore (prespore)
• Mother cell
Stage III: Mother cell engulfs the forespore
• Forespore surrounded by two membranes
Stage IV: Formation of the cortex
• THICK layers of peptidoglycan form between the two membranes
- HIGHLY cross-linked layer – CORE WALL (rigid & tough)
- LOOSELY cross-linked layer – CORTEX (~ 1⁄2 of spore volume) - big component of the whole thing
Stage V: Coat synthesis (external structure)
• PROTEIN layers surround the core wall (everything before this point was carb)
- Spore coat
- EXOsporium - outside of spore
- Protect the spore from chemicals and enzymes (that can potentially take place from outside of structure)
Calcium, dipicolinic acid and small acid soluble proteins (SASPs) accumulate in the core
• Help stabilize DNA
- b/c as it becomes dehydrated - that DNA will lose a lot of its stability - so having these chemicals in place inside the structure are gonna help to make sure the DNA is strong - b/c without water it tends to be destabilized
Stage VI: Endospore matures (maturation)
• Core is dehydrated - water leaves inside of structure
• ~ 10 – 30% of a vegetative cell’s water content (is left over, but still enough to ensure its stable, a good chance of keeping its core components safe, so if it becomes vegetative later - it can be successful in doing so
- but don’t have full water content so high heat for ex won’t be transferred to the delicate DNA structure
- shed 70-90% of water that a normal cell has
Stage VII: Mother cell is lysed = dead • Mother cell disintegrates BUT: • Mature spore is released - in a good spot in order to make sure it has the best chance for survival
& then, when conditions become fav., germination occurs
- exists spore state & in doing so becomes vegetative (metabolically active)
- protein syn, cell respir, binary fission etc.
Lifecycle of a spore forming bacterium OVERVIEW
Organism senses a depletion of nutrients & that trouble is coming
I - so it divides (pinches) & you will have 2 separate mem. bound structures
II
1. Mother cell - destined to DIE when this is over
2. Prespore - released endospore when this is over
- septum in middle - b/c think gram + PD layer will go around all mem. bound components
III - mother cell engulfs or endocytosis the forespore
- but forespore continues to have its own mem. & will have endosomial mem. outside that
- membrane bound structure in its own regard, then you take it in by forming another mem. on outside of that, so you get 2 mem’s
Sporulation stages
- Mother cell (vegetative/metabolically active)
- asymmetric cell division; commitment to sporulation, Stage I
- Engulfment - PD goes around all components - thick b/c gram +
- endosomal membrane
- anything endocytosis happens, it’ll be mem. bound
- forespores mem.
- cortex formation
- spore coat, Ca2+ uptake, SASPs, dipicolinic acid
- cell division & growth
- germination
- maturation, cell lysis
Flagella and Swimming Motility
• HOLLOW protein filaments
- Impart motility - think: airplane or boat (in fluid media not touching ground, much like how flagella are in media)
- freedom to move from 1 location to another, BUT DON’T need contact with a surface (airplane doesn’t have to touch ground to move)
- filament has flagella protein polymerized to create a hollow structure
Flagella and Swimming Motility MUST BE
STAINED to view
• Flagella stain
req’s a MORDANT b/c the filament is SO THIN (it becomes v. difficult to view with just standard microscopy)
- when you apply stain with a mordant - it bulkens up the structure, making it easier to visualize with a light microscope
Flagella and Swimming Motility, can be used for…
IDENTIFICATION • Monotrichous • Amphitrichous • Lophotrichous • Peritrichous
Monotrichous
– single flagellum
• Polar or subpolar
- polarized to 1 end of the cell or can be at a diff. location (sub)
Amphitrichous
Flagella at OPPOSITE ends
- could be just 1 on each end or more than 1
Lophotrichous
Multiple flagella in a single TUFT
think: hair being grabbed & twisted into a tuft which is LESS FLEXIBLE - MORE RIGID
Peritrichous
Flagella distributed around cell.
- higher # of filamentous structures
3 components of the Flagellar structure:
- Filament
- Hook
- Basal Body (motor)
Flagellar structure
- Filament
has polymerized flagellin protein, AKA produce flagellin protein according to the sequence of the DNA & then once the polypeptide is assembled, you take multiple pieces of it (having multiple lego blocks that are identical) & then put them together in an organized sheath in order to create the filament
- Rigid helical protein ~ 20 μm long (opp. to generate a large amount of thrust/power, which will propel the organism forward)
- Composed of identical protein subunits – FLAGELLIN
Flagellar structure
- Filament
composed of…
identical protein subunits – FLAGELLIN
What does the 3-D filament have on the inside?
NOTHING in there –> hollow
Flagellar structure
- Hook
- like a HINGE in a door - so the door can move a great deal (as a free range of motion b/c of that hinge that’s attached)
- or think: shoulder joint - allows arm to move in sign. ranges of motion
• FLEXIBLE coupling between filament and basal body
Flagellar structure
- Basal Body (motor)
MOST COMPLEX comp. of flagella
- involved in motor & ANCHORS the flagellin filament & hook into the actual structure of the cell; so as its rotating with great force - it’s not going anywhere (makes sure its attached well & strong so it can make those movements)
think: pectoral gurdle –> part of skeleton that’s stationary or analogous to the door frame
Flagellar structure
- Basal Body (motor)
Consists of:
Consists of central rod that passes through series of rings:
- L ring – LPS layer
- P ring – Peptidoglycan
- MS ring – Membrane
- C – ring – Cytoplasm (associated with membrane).
Flagellar structure
- Basal Body (motor)
L ring
– LPS layer
GRAM - ONLY
Flagellar structure
- Basal Body (motor)
P ring
– Peptidoglycan
GRAM + & -, attached to PD
Flagellar structure
- Basal Body (motor)
MS ring
– Membrane
- imbedded in OUTER leaflet of the PM (farthest away from cytoplasm)
GRAM + & -
Flagellar structure
- Basal Body (motor)
C – ring
– Cytoplasm (associated with membrane).
- on the INNER leaflet of the PM - in contact with the cytoplasm of the cell
Would the L ring of the basal body be present in gram +?
NO - b/c gram +’s DON’T have LPS layer
Flagellar movement
• ENERGY to turn the flagella comes from the PROTON MOTIVE FORCE (PMF)
think: need to put fuel (in flagella case it’s a proton gradient) in car to get engine & parts to move to drive a car (for it to move)
- Gradient of protons (H+) across the cytoplasmic membrane
- - High [H+] outside
- - Low [H+] inside
Let H+’s flow in & release lots of energy &…
• MOT PROTEINS form a channel that allows H+ to move into the cytoplasm
• Provides the energy to turn the flagellum
• Flagellum TURNS like a propeller to drive the cell FORWARD
Energy to turn the flagella comes from the…
proton motive force (PMF)
Mot proteins…
form a channel that allows H+ to move into the cytoplasm
- pore that has specificity for H+’s
Provides the energy to turn the flagellum
Flagellum ____ like a _____ to drive the cell ____
TURNS
PROPELLER
FOWARD
*corkscrew rotation
If you don’t let protons from ETC flow into the ATP synthase to make ATP, then…
the proton gradient still stores energy, but rather than getting it out in the form of ATP - you can use MOT PROTEINS part of the flagellin filament
- let protons from ETC flow in down [ ] gradient
- protons releasing energy that was stored
- as energy that was stored gets released - it’s used to drive CW or CCW rotation of the filament
- corkscrew rotation (think: propellor) - big circular motions vs. sperm tail moves - L to R (whip like fashion)
- diff. ways to generate thrust
Flagellar movement is a…
corkscrew rotation
Flagellar synthesis
• SEVERAL GENES are required for flagellar synthesis and motility
- need lots of recipes to build this complex structure
- MS ring is made first
- Other proteins and hook are made next
- Filament grows from tip
think: toys with rings that go down plastic stick to be stacked
Flagellar synthesis STEPS
- MS/C ring - goes into cytoplasmic mem.
- Mot proteins added
- P ring - go into THICK PD for gram +’s & THIN PD for gram -‘s
- L ring - go into gram - LPS (NOT in gram +)
- Early hook
- hinge made out of protein
- allows for free range of motion of the filament once motility begins - Cap - END of filament structure BUT gets assembled BEFORE the filament
- so cap & hook attached rn - Filament synthesis - flagellin polymer
- extend filament in b/t, by polymerizing flagellin protein
- hollow & provides motility
What is unique about the cap in the flagellar synthesis?
Cap is at the END of filament structure BUT gets assembled BEFORE the filament
- cap is attached to hook initially, then filament gets formed in b/t and cap winds up on the end
Flagella and Swimming Motility
Differences in swimming motions:
PETRITRICHOUSLY flagellated cells move SLOWLY in a STRAIGHT line
POLARLY flagellated cells move more RAPIDLY and typically SPIN around
POLAR flagellated cells…
move more RAPIDLY & typically SPIN around
think: guy on motorcycle with mullet
- Bundled flagella (CCW rotation)
- all hair (flagella) is behind as he is driving - TUMBLE - flagella pushed apart (CW rotation)
- when he stops, all hair goes messy
- tumble = stopping; happens b/c flagella switches direction of rotation - all peritrichous filaments switch from CCW to CW rotation
- NECESSARY for change in rotation! - Flagella bundled (CCW rotation)
- redirects itself - resuming in another direction now (CCW rotation)
Peritrichous
Reversible flagella:
goes forward or reverse, based on direction of rotation (CW or CCW)
- CCW rotation
- allows FORWARD direction - CW rotation
- moves in REVERSE
Peritrichous
Unidirectional flagella:
NOT reversible
- 1 direction of rotation only
- can make a lot of widespread movement b/c its going CW or CCW (1 rotation only)
- CW rotation
- allows it to move forward - Cell stops, reorients
- & resumes same rotation (CW) in another direction BUT same rotation (CW) - CW rotation
NOT all polarized flagella will be…
REVERSIBLE
REVERSIBLE flagella does NOT…
display TUMBLE & RUN
Gliding Motility
think: a car on the road - must always have tires contacting road surface for motion
- Flagella-INdependent motility
- Slower and smoother than swimming
- Requires surface contact
Gliding Motility
Mechanisms (that requires surface contact)
- Excretion of polysaccharide slime
- Type IV pili
- Gliding-specific proteins
Gliding Motility
Excretion of polysaccharide slime mechanism:
provides a SLIPPERY surface, which means that the motility will be EASIER, than if it was just the bacterium touching a surface that had more friction
think: foot on rock that’s slimey (falls/slips off) vs non slimey (able to stay stationary)
Gliding Motility
Type IV pili mechanism:
have twitching motility
- polymerize & depolymerize - creates twitching appearance
think: dancing on the spot
Gliding Motility
Gliding-specific proteins mechanism:
- protein extending from OUTER membrane
- allows organism to move/walk from point A –> B
Why does the protein need to be in OUTER mem.?
has to be able to CONTACT the surface
Magnetotaxis
allows movement according to magnetic field
- inclusion bodies that contained iron oxide & iron sulphides that provided magnetic properties to the cell, so the cell could orient itself & use the magnetic field as incentive for movement
Taxis:
directed (intensional) movement in response to CHEMICAL or PHYSICAL GRADIENTS
Chemotaxis:
response to chemicals
ex) Glucose: ATTRACTANT
- think: smelling a cinnamon bun sending signals that will get you to migrate to that
ex) Erythromycin: REPELLANT
- think: smelling something bad or concerning will signal your receptors to move away from it
What is the movement with respect to GLUCOSE? Will the organism be moving TO the glucose or AWAY?
TOWARDS - b/c its a carbon & nutrient source for ATP producion
- therefore an ATTRACTANT
What is the movement with respect to ERYTHROMYCIN (an ANTIBIOTIC)? Will the organism be moving TO the antibiotic or AWAY?
AWAY - b/c it knows its a protein syn. that’ll kill them
- a REPELLANT
Phototaxis:
response to light
ex) CYANOBACTERIA - photosynthesis
Aerotaxis:
response to oxygen
TOWARDS O2:
- obligate aerobe - needs O2
- facultative aerobe - switch depending on O2 availability –> will move towards for more energy
AWAY FROM O2:
1. obligate anaerobe - poisoned by O2 so choose to stay away rather than die
Osmotaxis:
response to ionic strength
(Na+, Cl-, K+ etc.)
- when these electrolytes are present in higher [ ], will serve as an attractive stimulus
- BENEFICIAL –> provide energy for symporters & therefore active transport for ex
- brings Na+ inside cell, releasing energy that can be used to move nutrients from LOW [ ]’s to high [ ]’s
Hydrotaxis:
response to water
*60-80% of the cell is water
What does a cell do when they’re in an envir. with NOT a lot of water, does it die or go to sleep?
sleep/dormant - metabolically INactive, just waiting to restore its metabolic activity b/c it gets more water content
- BUT if there’s a way to avoid this, b/c you see there’s adequate amounts of water in the distance, you’ll take that & move towards it to benefit the cell b/c its able to continue doing life - rather than falling asleep
Chemotaxis is best studied in…
E. coli - gold standard to be able to study a lot of diff. things
- b/c its easy to grow in the lab (quickly on min. nutrients, can use it to grow quickly & study gram - cell structure & motility b/c it has a peritricous flagellier arrangement)
- can also use it as a genetically engineered organism to do something
Chemotaxis bacteria respond to…
TEMPORAL, NOT SPATIAL, difference in chemical concentration
- TEMPORAL = changes in TIME
- rn there’s nothing, but all of a sudden there is some, that’s what they’ll respond to & move forward
- SPATIAL = changes from point A to B
- don’t care if where they are now, has less than before & vice versa
- that’s not what they’re responding to our moving to
*move ONLY when there’s a change in time, when [ ] finds itself higher they will move there b/c that change is taking place IN THE MOMENT
Chemotaxis executes the…
“Run and tumble” behavior
- same that peritrichous movement used
Chemotaxis are sensed by…
Attractants and repellants sensed by CHEMORECEPTORS
- picking up on chemical [ ]’s in the envir.
- could be sensitive to an attractive or repellant based on what an organism encodes within there genetic makeup & whether that chemical is characterized as an attractant or repellant would be the motivation (ex: receptor for penicillin, glucose etc.)
No attractant present:
Random movement
think: rabbit - hops in diff directions for no reason
Attractant present:
(chemoreceptors providing a) Directed movement - NOT happening in random series of tumbles
If rabbit sees something its fearful of, it’ll run in a zig zag (no pattern), even though they got scared by us & are trying to run away
- going straight, but doing so in a NOT direct way
think: going to other cities on way to Calgary
Chemotaxis
DIRECTED movement toward an attractant or away from a repellent
• Biased random walk
- looks like its random, but its headed to attractant or away from repellant
• The cell still exhibits a series of runs and tumbles
Chemotaxis Ex)
E. coli shows biased random walk TOWARD glucose when there is a concentration gradient
- having an increased [ ] of attractant makes them realize theres none where they are (temporal diff) so they go toward it
Chemotaxis
If it senses that the [glucose] is increasing:
(i. e. senses that it’s getting closer)
- will stop screwing around with tumbles & changes of direction & start extending walk to get their sooner b/c are anticipating it
think: making way to kitchen for cinnamon buns
- The TUMBLE is DELAYED - not doing as much
- The RUN lasts LONGER - get there sooner
Measuring chemotaxis
- Measured by inserting a capillary tube containing an attractant or a repellent in a medium of motile bacteria
- Can also be seen under a microscope
a) nothing - 1st inserted
b) after some time, equilibrate with equal spacing in tube that it has in the media - less competition (CONTROL - what we can compare experimental conditions & results to, to validate them)
c) attractant is something they really want
- all want to be in tube but not everyone will get to front of line/a space so they will be present in normal nutrient mixture that’s not full of that attractant, so their chemoreceptors aren’t even responding
- think: free trip to Hawaii
d) organism is gonna space out & want nothing to do with it
- have defective or no chemoreceptors or area diff. species that don’t have it as a repellant
Cell Size
Eukaryotes have:
• LOWER surface area to volume ratio
- Need more sophisticated transport mechanisms
r = 1 microm
- fills quickier (think: small venue)
r = 2 microm
- fills slower & results in slower growth
- think: MTS center during Jets game
SA/V
- want SA to be HIGH
- want V to be LOW
- want # to be LARGER b/c we can better DISTRIBUTE NUTRIENTS!
• GROW SLOWER
What do we want the # to be for eukaryotes cell size in terms of SA/V?
want # to be LARGER b/c we can better distribute nutrients!
Eukaryote (true nucleus)
• Genetic material is housed in a NUCLEUS (chromosomes are fenced off - so you can efficiently & accurately reproduce them, from DNA replication & also segregate them in 2 piles to allow for cell division to occur (think: fenced off yard so kids don’t run off & you can keep an eye on them)
- organized & protective –> min. likelihood for chromosomal error during cell division
- Generally LARGER than prokaryotes
- COMPLEX internal structure
- Membrane BOUND organelles (compartmentalizes - does catabolism/anabolism etc. in DIFF organelles)
- 3 bedroom apartment - organization makes things like metabolism, digestion etc. happen easily)
• Intra-cytoplasmic membranes used for TRANSPORT
- Endoplasmic reticulum & golgi is used for IC transport through vesicles (opp. to send things to where they need to go)
- called ENDOMEMBRANE SYSTEM (together with nuclear mem.)
• CYTOSKELETON
- protein framework inside cell - allows for organelle motility, ability to fix things into position, & also cell structure
• Divide by MITOSIS (asexual - like prok. binary fission) and MEIOSIS (sexual - 1/2’s the chromosome #)
For a BACTERIAL cell, where would catabolism/anabolism take place?
all in CYTOPLASM –> b/c no options in a prok., everything has to take place there
- metabolic umbrella in a prok. is reduced
What is the “Intra-cytoplasmic membranes used for transport” in Eukaryotes called? & what are they?
called ENDOMEMBRANE SYSTEM
endoplasmic reticulum & golgi is used for IC transport through vesicles (opp. to send things to where they need to go)
Some Key Characteristics for PROKARYOTIC Cells
Size of cell: Typically 0.2 – 2.0 um diam.
Nucleus: NO nuclear membrane or nucleolus - for ribosome assembly (nucleoid)
- BUT has a NUCLEOID REGION - area where if you were to go there you’d have a good chance of seeing a chromosome
Membrane-enclosed organelles: Absent
Ribosomes: Smaller size (70S)
Chromosomal DNA: Singular, circular (just 1)
Cell division: Binary fission - used for GROWTH
- asexual - produce genetically identical daughter cells; provided there was no error in the division process
Some Key Characteristics for EUKARYOTIC Cells
Size of cell: Typically 10 -100 um diam.
~100x LARGER than proks
Nucleus: TRUE nucleus with nuclear membrane and nucleolus - ribosome assembly site (allows opp. for ribosome assembly)
Membrane-enclosed organelles: Present (e.g. Golgi, mitochondria, chloroplasts, etc.)
Ribosomes: Larger size (80S)
- characterize CYTOPLASMIC Euk ribosomes
- also have 70S in mitochondria (every Euk will have this) & chloroplast (if present)
Chromosomal DNA: Multiple linear chromosomes with HISTONES (unique to euk)
Cell division: Mitosis - used for GROWTH/REPAIR
- asexual - produce genetically identical daughter cells; provided there was no error in the division process
What is the purpose of histones in Euk cells?
- used to organize it, so DNA doesn’t get tangled & messy
- allow it to be compact b/c there is so much genetic info that needs to be stored in a tiny nucleus
- needs to have a really organized, tightly compacted structure which is super coild
think: DNA as hair
think: hairclips
What do we call DNA & histone proteins together?
CHROMATIN
Compare & contrast b/t the diff cell divisions
–> Binary Fission in Prok. & Mitosis in Euk
Binary Fission in Prok. - used for GROWTH
Mitosis in Euk. - used for GROWTH/REPAIR
BOTH ASEXUAL - both produce genetically identical daughter cells; provided there was no error in the division process
The Nucleus
• The nucleus holds the genetic information
• Multiple linear dsDNA chromosomes
- characteristic of ALL LIVING CELLS
3D
contains pores - essential to allow EXPORT of ribosomes from the nucleolus, EXPORT of mRNA (therefore can be used for translation), & IMPORT of proteins to allow for ribosome assembly, for DNA histone proteins to be entering etc.
Chloroplasts
- Site of photosynthesis
- Chlorophyll (concentrated in thylochoid mem’s of the grana - in order to allow for light absorption)
- Surrounded by 2 membranes
- DNA and ribosomes (70S)
Chloroplasts origin
= CYANOBACTERIA (that became trapped inside a larger cell which now has the opp. to do photosyn. inside of a Euk.)
associated with endosymbiotic theory
Mitochondria
site of catabolic rxn –> will do fat oxidation, TCA cycle, AA’s breakdown etc.
• Site of respiration and oxidative phosphorylation (AKA ETC)!!!
- where CO2 is produced & O2 is utilized - both requirements & wastes for respiratory gases will be produced & utilized in this structure
- through a series of redox rxns, you transfer e-‘s to O2, which produces a protein gradient to be used to stick a phosphate group on ADP forming ATP in bulk for the cell - oxidative phosph. (28 ATP/glucose)
- Surrounded by 2 membranes
- DNA and ribosomes (70S)
Mitochondria origin
= Ricketsia spp.
- obligate intracellular parasite
If mitochondria was at 1 point a bacterium, which of the 2 mem’s was the PM of that bacterium?
the INNER - b/c of the ETC
When mitochondria got internalized, how many mem’s were there actually?
3
How many mem’s are there in actual mitochondria organelle?
only 2 - so at somepoint 1 of them was lost
- but we know a bacterium uses its PM for its ETC & it has ETC in INNER mem. so inner mem. must be the PM
- the OUTER mem actually has porins inside
If mitochondria has porins inside of outer membrane, what does it mean in terms of which mem. was lost?
endospore mem.
So, in a mitochondria, there are 2 layers not 3 and they are…
- PM
- Outer membrane
- Endosome membrane - is GONE
What is the SA/V ratio in prok & euk, & which is better?
PROK:
- HIGH SA/V = better able to distribute nutrients
EUK:
- LOW SA/V = worse
- translates into SLOWER growth rate - harder to power the cell
Is there a diff. in function b/t prok & euk?
NO diff. b/t function of prok & euk
- both can catabolize glucose to produce ATP, both can produce protein, both can do anabolic rxns to build the molecules that are needed to assemble cell & keep it alive etc.
- just that 1 tends to be more complex!
- just increases cost, time to build & cost to maintain
Humans for ex (euk cell) have…
heightened complexicity which can allow for better compartmentalization
- b/c not only do we have to keep the 1 cell alive & functional, but we need to produce EC mediator (like cytokines for immune system, hormones which are necessary to control metabolism, Ca2+ balance etc.)
- therefore, having higher organization allows us to do more complex tasks in a more efficient manner
- whereas prok. cell is only 1 guy that stands alone, so he only needs to care for that 1 cell & there’s not really much complex communication or engagement with other cells that take place
Describe what membrane bound organelles like mitochondria allow for?
mitochondria is largely responsible for catabolic rxns
cytoplasmic location is anabolic rxns
therefore, membrane-bound organelles allows us to have diff. components for diff. things - makes it more efficient
What do intra-cytoplasmic membranes allow for?
allow opp. to ANCHOR organelles into position
- can tie a ribosome or mito onto protein framework so they can stay
- ER & golgi, lysosomes & PM
Imagine if you were standing with NO cytoskeleton to allow organelles to stick onto, what would happen if you’re in an upward position to all the cells & contents in your body?
gravity will make a puddle of organelles at bottom of the cell –> not good for function b/c needs organization, separation & space
What do the nuclear pores in the double mem. structure do there?
b/c needs to let mRNA out & proteins made by ribosomes
- provide permeability aspect
Chloroplasts 4 main points
- Photosynthetic
- Double mem. with 70S ribosomes within
- Circular piece of DNA
- Chlorophyll provides the capacity to do light absorption (to convert light into chemical energy in the form of ATP)
Chlorophyll
primary pigment that increases capacity for light absorption
- get more absorbed wavelength’s converted into chemical energy if you imploy more pigment that have diff. capabilities for absorption
