Chapter 3 lecture notes Flashcards
All prokaryotes don’t have?
Cytoskeleton.
A prokaryotes shell is made of?
Sugar and protein. The rigid structure works as exoskeleton to keep shape & cell from bursting
The pili on prokaryotes adhere to?
Substrates & glue to each other using capsules
Sperical round shape
Coccus
Rod shape
Bacillus
Short round rod
Coccobacillus
Curved rod
Vibrio
Spiral shape
Spirillus. Fiber in cell wall allows to curve on itself
Helical shape, tight coiling
Spirochete
Vary in shape
Pleomorphic. Can assume different forms
Diplobacilli=
2 bacilli
Streptobacilli=
String
Prokaryotic cells may form groupings
After cell division. Cells adhere together after cell division for characteristic arrangements. Arrangements depends on plan of division
Division along two or three perpendicular planes form
Cubical packets
Division along several random planes form
Clusters
General function of capsules and slime layer of glycocalyces
Protection and attachment.
Protection: Protects bacteria from host defenses
Attachment: Enables bacteria to adhere
Organized layer of sugar=
Disorganized layer of sugar=
Organized= capsule Disorganized= slime layer
Distinct gelatinous layer
Capsule
Irregular diffuse layer
Slime layer
Chemical composition of capsules & slime layers varies depending on bacterial species. Most are made of?
Polysaccharides
Glyco=
Calyx=
Glyco= Sugar Calyx= Shell
Cell wall of bacteria 6 main points
1) Rigid structure
2) Surrounds cytoplasmic membrane
3) Determines shape of bacteria
4) Holds cell together
5) Prevents cell from bursting
6) Unique chemical structure (distinguishes Gram + from -)
The rigidity of the bacterial cell wall is due to?
Peptidoglycan (PTG)
The basic structure of peptidoglycan
Peptido=protein
Glycan=sugar
Alternating series of two subunits; N-acetylclucosamine (NAG) and N-aceetylmuramic acid (NAM). Joined subunits form glycan chain and the chains are held together by string of four amino acids (tetrapeptide chain)
What are the sugars in peptidoglycan
N-acetylglucosamine (NAG)
N-acetylmuramic acid (NAM)
Gram-positive cell wall
1) Relatively thick layer of peptidoglycan (PTG)
2) As many as 30 layers of PTG chains
3) Teichoic acid component of PTG
4) Gives cells a negative charge
Main points about prokaryotes
1) Lack nucleus
2) Lack various internal structures bound with phospholipid membranes
3) Small ( ~ 1.0 micrometers in diameter)
4) Simple structure
5) Include bacteria & archaea
6) Do not have cytoskeleton
7) Shell is made out of sugar & protein
8) Capsules are important infector in disease
9) Flagellum responsible for motility, different than eukaryotic cells
10) Pili adheres to substrates & glue to each other using capsules
Gram-negative cell wall main points (4)
1) More complex than Gram +
2) Only contains thin layer of peptigoglycan (3-10)
3) PTG sandwiched between outer membrane and cytoplasmic membrane
4) Region between outer membrane and cytoplasmic membrane is called periplasm ( most secreted proteins are contained here, proteins of ABC transport system are located here)
Cytoplasmic membrane main points
1) Selectively permeable
2) Molecules pass through membrane via simple diffusion or transport mechanisms that may require carrier proteins & energy
Simple diffusion
Molecules move freely across the cytoplasmic membrane like H20, some gases & small hydrophobic molecules pass via simple diffusion
Facilitated diffusion main points (3)
1) Moves compounds in the direction of the concentration gradient (from greater concentration to lesser)
2) Molecules diffuse until equilibrium is reached (system can only eliminate concentration gradient; it cannot create one)
3) No energy required
* Example movement of glycerol into the cell
Some bacteria have protein appendages which are not essential for life. They aid in survival in certain environments. They include?
1) Flagella
2) Pili
Flagella are
Long protein structure that is responsible for motility.
- Use propeller-like movements to push bacteria
- Can rotate more than 100,000 revolutions/minute (Equivalent to a 6 ft man running 82 mile/hour)
- Some important in bacterial pathogenesis (H. pylori penetration through mucous coat)
3 basic parts of flagella
1) Filament- Extends to exterior. Made of proteins called flagellin
2) Hook- connects filament to cell
3) Basal body- anchors flagellum into cell wall
Bacteria use flagella for
Motility. Motile through sensing chemicals (chemotaxis) if the chemical compound is a nutrient it acts as attractant. If the compound is toxic it acts as repellent
Bacteria can have flagella and pili, the pili are?
Considerably shorter and thinner than flagella. They have a similar structure (protein subunits). They function to attach, which are called fimbriae, movement, and conjugation, mechanisms of DNA transfer.
Differences in cell wall account for differences in staining characteristics
Gram-positive bacterium retain crystal violet- iodine complex of Gram stain-purple
Gram-negative bacterium lose crystal violet-iodine complex-pink
Some bacteria lack cell wall
Called Mycoplasma.
- Causes mild pneumonia
- Sterols in membrane account for strength of membrane
If a bacteria doesn’t have a cell wall then what can happen?
Antimicrobial drugs directed against cell wall are ineffective
Bacteriain Domain Archaea
Have a wide variety of cell wall types
– None contain peptidoglycan but rather pseudopeptidoglycan in some
Cytoplasmic membrane proteins
Membrane is embedded with numerous proteins
– More than 200 different proteins
– Proteins function as receptors and transport gates
– Provides mechanism to sense surroundings
– Harvest light energy in photosynthetic bacteria
– Proteins are not stationary. Constantly changing position. Called fluid mosaic model
Osmosis is
Simple diffusion of H2O
– H2O flows freely across the cytoplasmic membrane
– H2O flows to equalize solute concentrations inside and outside the cell
– Inflow of H2O exerts osmotic pressure on membrane (Membrane rupture prevented by cell wall)
Two primary forms of energy
ATP & Proton motive force
3 mechanisms for active transport
– Uniport
– Antiport
– Coupled Transport (Uniport & Symport)
Alters the molecule
Group translocation
Movement of many molecules directed by
Transport systems:
– Transport systems employ highly selective proteins
– Transport proteins include permeases, channels, or ports
– These proteins span membrane
* Single carrier transports a specific molecule
* Most transport proteins are produced in response to need
Transport systems include:
Facilitated diffusion
Active transport
Group translocation
Storage granules / Inclusions is
Accumulation of polymers
- Synthesized from excess nutrients
Example is glycogen-excess glucose in cell is stored in glycogen granules
Gas vesicles main points
1) Small protein compartments
2) Provides buoyancy to cell
3) Allows organism to reach ideal position in environment
Endospores main points
1) Dormant cell types
- Produced through sporulation
- Theoretically remain dormant for 100 yrs
2) Resistant to damaging conditions
- Heat, desiccation, chemicals and UV light
3) Vegetative cell produced through germination
- Germination occurs after exposure to heat or chemicals
- Germination not a source of reproduction
4) Not affected by crenation
Essential for translation (proteins)
Ribosome
Site of protein synthesis, composed of large and small subunits, units make of riboprotein and ribosomal RNA
Ribosome
Prokaryotic ribosomal subunits
Large=
Small=
Total=
Large=50S
Small=30S
Total=70S
Eukaryotic ribosomal subunits
Large=
Small=
Total=
Large=60S
Small=40S
Total=80S
The difference in ribosomal subunits of prokaryotic and eukaryotic cells is often used as?
A target for antimicrobials
In a prokaryotic cell division along two or three perpendicular planes form?
Cubical packets, example Sarcina genus
In a prokaryotic cell, division along a single plane may result in?
Pairs or chains of cells
- Pairs= diplococci, example Neisseria gonorrhoeae
- Chains= streptococci, example species of Streptococcus
