Cell Structure and Function in Bacteria and Archaea

Created by ritchelschultz 

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Cell Morphology

Key features of prokaryotic cell: "form follows function"
-shape and small size
-shape and arrangement

Cell Shape

-Coccus = Spherical shape
-Bacilli = Rod shape
-Coccobacilli =Short rod also looks like a sphere
-Vibrios = Curved rods (spiral)
-Spirilla = Helical and rigid
-Spriochetes = Helical and flexible

Cell Arrangement

-Diplo = Pair
-Strepto = Chain
-Staphylo =Cluster
-Palisades = Chain side by side
-Tetrad = packs of 4
-Sarcina = Packets of 8

Appendage Bacteria

Extensions of their cell as long tubes or stalks

Filamentous Bacteria

Form long thin cells or chain of cells

Pleomorphism

You expect a particular shape but get a different result because cells have been disrupted in shape and arrangement.
Many factors that take in place (old specimen, denatured, heat fixed too long)(ei. protein describes E.coli is a rod shape but you heat fixed it too long and you see
cocci.
DEFAULT is COCCI

Significance of Cell

Small cells with high surface to volume ratio.
-Lower limit: If a cell is too small it will not have enough space to house all of its organelles and other necessary materials.
-have higher surface-to-volume ratio support greater nutrient exchange p/ unit of cell volume
-Upper limit: if cell grows too large, it's surface area/volume ratio decreases and it will not absorb nutrients or release wastes efficiently

Sulfur Chemolithotroph (Thiomargarita)

-largest known prokaryote
-lg. cell size to store sulfur as source of energy

mutations

-changes in DNA that alter the expression of certain genes
-raw materials for evolution
-rapid growth and evolution

Prokaryotic Cell

External= Appendages/Flagella/Pili/Fimbriae
Glycocalyx/Capule/Slime Layer
Envelope= Outer membrane/Cell wall/Cell
membrane
Internal= Cytoplasm/Ribosomes/Inclusions/
Nuclioid/Chromosomes/Actin/Endospore

Cytoplasmic Membrane

=a thin barrier that surrounds the cell and separates the cytoplasm from the cell's environment
=highly selective permeability barrier, enabling
a cell to concentrate specific metabolites and excrete waste materials

Cell Membrane Permeability

are made mostly of lipids and
proteins. Phospholipids are found in the cell membrane and form two layers called the lipid
bilayer.
Active and passive systems;
1)Size of molecules
2)Solubility
3)Channels or carrier molecules

Selective Permeability

A property of biological membranes that allows some substances to cross more easily than others.

Composition of Membrane

Two major components are lipids and proteins. There is a lipid bilayer - two rows of phospholipids, each with their polar hydrophilic heads toward the outside of the membrane and their non polar hydrophobic tails toward the water free interior.

Phospholipid

-A molecule that is a constituent bilayer of cell membranes: having a polar(charged) hydrophilic head and a nonpolar, hydrophobic tail
-phosphate group attached to glycerol , two fatty acids (saturated and unsaturated)

Saturated Fatty Acid

-A fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thereby maximizing the number of hydrogen atoms that can attach to the carbon skeleton. Strait.
-Higher melting temp

Unsaturated Fatty Acid

-A fatty acid that has one or more double bonds between carbons in the hydrocarbon tail and thus lacks the maximum number of hydrogen atoms. Bent or Kinked.
-Low melting temp

Purpose of Lipid

To find balance
-too much fluid (no orientation)
-too solid (can't pass things in and out of cell)

Unit / Leaflet

One Phospholipid layer (top or bottom)
A membrane has two units or leaflets of phospholipid layer

SINGER 70's

Membrane is a FLUID MOSAIC MODEL

Membrane Proteins
-Core chemistry governed by lipids
-Proteins are embedded within
-Dynamic

Integral (Transmembrane or Intrinsic)
=firmly embedded in the membrane
Peripheral = firmly associated on the surface of
the membrane
Lipoproteins= (Lipid Anchored =peripheral)
contain a lipid tail that anchors the
protein into the membrane.
= important in energy metabolism
and transport

Freeze Fracture Technique

Freeze the cells. Membrane will split along the hydrophobic seam.

Transport Proteins

Integral = used as transport channels shipping
things in and out.
=It is amphipathic (hydrophilic and
hydrophobic areas)
Peripheral=located on one or the other leaflets.
Structural and anchoring, supply
energy
Lipid Anchored = sitting on top of membrane
anchored by a lipid. (Signaling in
membrane)

Dynamic Membrane

it is constantly changing because of fluid structure that response to situation
=change location of proteins content
=change location of fatty acids

Hapanoids

=Plasma membrane strengthening and rigidity in bacteria.
=adjust cell permeability and adaptation to extreme environmental conditions.

Archaeal Membrane (Extremophiles)

=Ether linkages of hydrocarbon side chains to glycerol Glycolipids
=Lipid monolayers Repeating Isoprene units resitant to peeling apart.
=Lipids lack fatty acid
=Non unit membrane cuz they are fused together

Proton Motive Force

Responsible for driving many energy-requiring function in cell including Transport, Motility and Biosynthesis of cell's energy currency ATP

Permeability Barrier (Membrane)

=Prevents leakage
=Functions as gateways for transport of nutrients in and out of cell

What is Permeable to Membrane?

=H2O freely penetrate membrane cuz it is accelerated by aquaporins(transport protein)

Transport Proteins

-taxi substances across the membrane
-accumulate solutes against the concentration gradient

=Saturation Effect (properties)

substrate is high enough to saturate transport. Rate of uptake is maximal and addition of substrate does not increase rate

=High Specificity (properties)

Carrier proteins only react with a single molecule,

=Regulated (properties)

Specific complement of transporters present in the membrane at any given time is a function of both the nutrients present in the environment and their concentrations

Transport Systems
-Simple Transport
-Group Translocation
-ABC System (ATP-binding cassette)

-Simple= run of concentration gradient
(driven by energy in the proton motive
force)
-Group translocation= involved as series of proteins in the transport event(move n transfer a phosphate (chemical modification of transported substance driven by phosphoenolpyruvate)
-ABC System=Substrate binding protein
=Membrane integrated protein
=ATP-hydrolyzing protein
(periplasmic binding proteins are involved and energy comes from ATP) ATP--ADP+P

Transport Events

=Uni-move one solute in one direction
=Antiport- one molecule goes in and one molecule go out at the same time(Na and K pump) in the intestine.
=Symport-transport a molecule along with another substance.

Not all prokaryotes have cell wall

-Eubacter(Mollicutes) have mycoplasms
-Archaea (paracnystalline)

Protein Export Out
(via Secretory enzyme Translocases)
-important to bacteria cuz many bact. enzymes function outside the cell wall
(exoenzymes)

SecYEG= transmembrane transporter
SecA=ATP hydrolizing enymes(provide energy)
SecB=prevent folding of proteins
SecD,F= assist in translocation process(consume energy from proton motive force)

Hydrolytic Amylase / Cellulase

=excreted directly into the environment where they cleave starch and cellulose w/c is used by cell as carbon and energy source.

Type III secretion system

=bacteria protein toxins excreted by a second translocase system

Cell Walls of Prokaryotes
gram-positive=much thicker and consist of entirely one molecule
gram-negative=multilayered structure and complex

Bacteria cell contain high concentration of dissolved solutes causing osmotic pressure

Osmotic lysis

When water flows into a cell and the plama membrane bursts due to pressure. The cell wall protects against this.

Cell Wall

=gives shape and rigidity to the cell
=helps regulate water movement

Gram stain reaction

Distinction between: positive = purple
negative = pink

Components of Gram-positive cell wall
(have up to 25 sheets of peptidoglycan)

=Peptidoglycan outer layer (protein n sugar)90%
=Cytoplasmic membrane

Peptidoglycan

A large polymer composed of long chains of alternating N-acetyl-glucosamine and N-acetylmuramic acid residues. The polysaccharides chains are linked to each other though connections between tetrapeptide chains attached to the N-acetylmuramic acids. It provides much of the strength and rigidity possessed by bacterial cell walls

Componets of Gram-negative cell wall

Outer membrane= Lipopolysaccharide n protein
Periplasm= Peptidoglycan in between outer n
inner (cytoplasmic )membrane
Cytoplasmic membrane

LPS (Lipopolysaccharide)

imbedded in between leaflets
O specific
Core polysaccharide
A specific {edotoxin

L-forms

organisms that normally would have cell wall but lost it in response to mutation in wall forming genes or artificial loss due to antibiotic or chemical: *still functional,
phase of a cell that it looses its cell wall, induced naturally or artificially

Teichoic Acids

=Include all cell wall, cytoplasmic membrane, and capsular polymers containing glycerophosphate or ribitol phosphate residue.,
= _____ are unique to Gram (+) species and impart an overall
negative charge to the cell. They are involved in structural support and
ion transport via the attraction of cations (Mg 2+ , Na + ) to the cell surface

lipoteichoic Acids

=some teichoic acids that are linked to the cytoplasmic membrane found in gram positive cell

Lysozyme

• Found in perspiration, tears, saliva, nasal secretions and tissue fluids
• Breaking down cells calls of gram + bacteria and, to lesser extent gram -
• Lysozyme breaks chemical bonds on peptidoglycan which destroys the cell wall

Protoplast

A bacterial cell whose cell wall is completely lacking and that is vulnerable to osmotic lysis.

Spheroplast

=Contain pieces of wall material attached to the membrane enclosed structure.
=A relatively spherical cell formed by the weakening or partial removal of the rigid cell wall component (e.g., by penicillin treatment of gram-negative bacteria). Spheroplasts are usually osmotically sensitive.

Mycoplasmas Group

=A group of pathogenic bacteria that causes a variety of infectious diseases in humans and other animals.

Thermoplasma Group

=Species of Archaea that naturally lack cell walls
=Prokaryotes are free-living protoplast that are able to survive w/o cell walls bec. of tough cytoplasmic membrane

Protoplast and their Formation

= In a Low Solute solution Lysozyme breaks the B-1,4 glycosidic bonds in peptidoglycan breaking down the cell wall and is immediately lysed bec. the cytoplasmic membrane is structurally weak.
=In an Isotonic solute solution such as sucrose, water does not enter the protoplast and it remains stable.

Outer membrane of Gram-negative Bacteria

=10% of cell wall consist of peptidoglycan
=Most of cell wall is composed of outer membrane

LPS lipopolysaccharide layer (outer membrane)

LIPID and POLYSACCHARIDE are linked to form a complex
Polysaccharide =O-polysaccharide specific(all hexoses)
Core polysaccharide (Ketodeoxyoctonate
KDO)
Lipid = Lipid A (endotoxin)

E.coli K12(used in lab)
E.coli O157(hemorrhagic bloody diarrhea)
What recognizes and come in contact with the bacteria from my immune system? The Antibody and will recognize the antigen(O-specific thus O157)

Determined by
O-specific region
LipidA (in the membrane and part of cell ENDOtoxin)

Lipoprotein

=Functions as an anchor bet. outer membrane and the peptidoglycan

Porins

=a type of protein in the outer membranes of gram negative bacteria that permits passage of small molecules such as nucleotides and amino acids

Non specific Porins

Form water channels through which small molecules of any kind can cruise freely

Specific Porins

Highly specific porins and have binding site specific for a single compound or group of closely related substances.

Periplasm

the space that lies just inside of the outer membrane and cytoplasmic membrane in gram-negative bacteria. it contains the cell's peptidoglycan wall within it. it is filled with gelatinous material, including two types of proteins. One is enzymes, which can pass through the cytoplasmic membrane, and the second protein are binding proteins....which bind cerain nutrients and facilitate their passage across both the outer membrane and the cytoplasmic membrane

Gram Stain

has four steps. 1. Primary stain: crystalline violet that stains all bacteria purple 2. mordant: Gram's iodine sets the stain 3. decolorizer: ethanol washes out the stain from gram negative bacteria only 4. counterstain: safranin stains gram negative bacteria pink

Pseudomurein (Archaea)

A modified peptidoglycan lacking D-amino acids and containing N-acetyltalosaminuronic acid instead of N-acetylmuramic acid; found in methanogenic archaea.

S-Layers (Archaea)

regularly structured layers of protein or glycoprotein; external to the cell wall in bacteria; may be only thing outside Archaeal plasma membranes

Capsule

=A sticky and sugary layer that surrounds the cell walls of some bacteria, protecting the cell surface and sometimes helping to glue the cell to surfaces.
=Helps to avoid detection/destruction by immune system

Slime Coats

=Helps to stabilize against loss of H2O(turgor) and nutrients
=thin and loose and can be lost from the cell surface

Biofilms

=Start as moist, sugary layers on substrate surface
=Surface coating colonies which secrete signalling molecules that recruit nearby cells causing the colony to grow. These cells also produce proteins that adhere to substrate and allow nutrients to reach the center and for wastes to be expelled.
=Plays some role in resistance of the cell to desiccation

Fimbriae

=Non-motile, sticky, short bristle like projections, cells (bacteria) use them to stick to eachoter & stuff around them (neisseria gonorrhea attches to membrane of reproductive tract)
=from membrane to cell wall for attachment(arrangement of staph attach together or even stick to our skin regardless of washing

Pili

=Tubular extension used for conjunction in facilitating genetic exchange bet. prokaryotic cell.
=Longer than the fimbriae.
=Only one or a few pili are present on surface of cell
=Pili IV twitching for movement

Storage Bodies
Inclusions (bacteria)

=Varying organic content (Glycogen storage of sugar polymer)
ex.
PHB(Poly-B-Hydrocxybuteric Acid C4-C18)
PHA(Poly-B-Hydrocxyalkanoate Acid =Carbon and energy
storage molecule break down to make ATP)

Storage Bodies
Granules-inorganic substance

=Energy reserves (Carbon)
=Polyphosphates - ATP
- Phospholipid bilayer of membrane
- DNA = phosphate in nucleotide
=Sulfur- elemental sulfur globules accumulate inside cell
=Magnetosomes - Magnetic storage (orients cell in direction)
= Aquatic bateria Fe3O4
=Gas vesicles
=Purple/Green bacteria(gas vesicles)
= Cyanobacteria
spindle shape granules carry 1amt pressure of gass is 5-20% of bacteria's volume it will make it float because it becomes buoyant

Gas Vesicle Protein (GVP)

=organisms can float bec. of gas vesicles
=common in aquatic bacteria and phototrophic bacteria.
=spindle shape granules carry 1amt pressure of gass is 5-20% of bacteria's volume it will make it float because it becomes buoyant

Endospore (Cell within a cell with protective layer)

=A small, rounded, thick-walled, resting cell that forms inside a bacterial cell
=survival structure is extremely resistant to heat, harsh chemical and radiation
=it has dna, membrane, cell wall, spore coat(won't allow us to stain it so it comes out clear) so we use a stain

Endospore forming bacteria

Bacillus & Clostridium

Bad stimulus for Endospore

=Chemical treatment
=Lack of nutrients / Waste (ph)
=Lack of water

Vegetative Cells

=cells that grow and reproduce, this is found when favorable condition return and they are the result of endospores
vegetative cell - endospore - vegetative cell

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