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Functional Anatomy of Prokaryotes and Eukaryotic Cells
Terms in this set (61)
- have a prenucleus (nucleoid)
- are smaller, simpler
- DNA is usually one circular chromosome (not enclosed in a membrane)
- no histones
- no organelles
- peptidoglycan cell walls
- 70S ribosomes
- divide by binary fission
- e.g., bacteria
- have a true nucleus
- larger, more complex
- DNA is contained in multiple chromosomes and is surrounded by a nuclear membrane
- has histones
- has organelles
- cellulose, chitin cell walls (if they are present)
- 80S ribosomes + 70S in organelles
- divide by mitosis
- e.g., fungi, protozoa, algae, plants, animals (including us)
What are the 3 different shapes of bacteria cells?
- sphere shape
- can be oval, elongated, or flattened
- means "berries"
What are the 5 coccus formations after cell division?
1. diplococci (pairs)
2. streptococci (chains)
3. tetrad (groups of 4)
4. sarcinae (cubes)
5. staphylococci (clusters)
- spherical shaped bacteria in pairs
- spherical shaped bacteria in chains
- spherical shaped bacteria in groups of four
- spherical shaped bacteria in cube formation
- spherical shaped bacteria in clusters
- rod- shaped
- means "little staffs"
What are the 4 bacillus formations?
1. single bacillus
- one singular rod-shaped cell
- two rod-shaped cells joined together
- multiple rod-shaped cells attached together
- kind of an oval-shaped bacillus cell
- not a circle like coccus but not a rod like bacillus
- in the bacillus family though
What are the 2 ways that "bacillus" can be used?
1. as the shape of a bacterial cell (not capitalized, not italicized)
2. as a genus name (capitalized, italicized)
- cell shape
- have one or more twists (never straight)
What are the 3 types of spiral cells?
1. vibrios (curved rods)
2. spirilla (helical, rigid)
3. spirochetes (helical, flexible)
- spiral family
- called a "curved rod"
- spiral family
- helical and very rigid
- thicker than spirochetes
- spiral family
- helical and flexible (skinnier than spirilla)
What are the structures located outside the prokaryotic cell wall?
- axial filaments
- "sugar coat"
- external to cell wall
- viscous, gelatinous polymer
- polysaccharide and/or polypeptide
- made inside & secreted to cell surface
- if organized and firmly attached it is called a CAPSULE
- if unorganized and loosely attached it is called a SLIME LAYER (e.g., extracellular polymeric substance)
- seen by negative staining
- can contribute to bacterial virulence
- protects from phagocytosis
- about twice the thickness of the actual cell
Extracellular Polymeric Substance (EPS)
- a type of glycocalyx (slime layer) that helps cells in a biofilm attach to target environment and to each other
- a microbial community that usually forms as a slimy layer on the surface
- has medical significance
What is the medical significance of a biofilm?
- they can form on any surface, including the surfaces of medical devices
What is the job of the glycocalyx?
- permits survival as it enable bacteria to attach to diverse surfaces
- protects from drying and phagocytosis
- facilitates cell to cell communication
- protects from antibiotics
- allow/enable bacteria to move
- contribute to virulence of some pathogens
- may be peritrichous
- or may be polar:
- having flagella distributed over the entire cell
- having a single flagellum
- having two or more flagella at one end of a cell
- having flagella at both ends of a cell
What are the 3 types of polar flagella?
- prokaryotic cell flagella protein
- important clinically for identification of different types of gram-negative serovars (variations within a species)
- e.g., E. coli O157:H7 - the H7 = this particular strain has H antigen #7
- a variation within a species
- aka: serotype
- responsible for spirochete motility
- bundles of fibrils from ends of the cell will spiral around the cell & beneath the outer sheath
- rotation of these filaments produce corkscrew motion of the cell
- allows movement through body fluids
What kind of movement do axial filaments give?
- corkscrew motion
What shaped bacteria cells have axial filaments?
- just spirochetes (think, rigid, spiral-shaped bacteria)
Fimbriae & Pilli
- found on gram-negative bacteria
- are hair-like appendages
- tend to be shorter, straighter, and thinner than flagella
- consist of pilin protein
- occur at poles or are evenly distributed
- few to several hundred per cell
- attach to each other and to surfaces (PRIMARY FUNCTION)
- important in virulence
- longer than fimbriae and less numerous (1-2 per cell)
What are the two types of pili?
1. type IV pilli
2. conjugation pili
Type IV Pili
- provide motility
- bring cells together allowing transfer of DNA from one bacterium to another (bacterial conjugation)
- aka: sex pili
- contributes to antibody resistance
- complex, semi-rigid structure
- most bacteria have one of these (not always)
- animal cells (like ours) do not have one
- made up of peptidoglycan in bacteria
What are the 3 main jobs of the cell wall?
2. protection from bursting in hypotonic environments
3. anchors flagella
Why is it important to know if certain cells have cell walls when deciding on antibiotics?
- some antibiotics target cell wall synthesis and wouldn't be effective if there was no cell wall on the target cell!!
What is the cell wall made up of in bacteria?
- Polymer of N-acetyleglucosamine (NAG) and N-acetylmuramic acid (NAM) ("glycan" part)
- has attached polypeptides ("peptido" part)
Cell Wall Structure
- chains of NAG and NAM form carbohydrate "backbone"
- tetrapeptides (4 AAs) attach to NAMs
- cross-linkages form between tetrapeptide chains
- gram - : tetrapeptides joined directly
- gram + : tetrapeptides joined by peptide crossbridges
Gram Positive Cell Wall
- thick layer of peptidoglycan
- teichoic acids
- polymers made of an alcohol (e.g., glycerol) and phosphate
- bind cations (Ca2+, Mg2+) for eventual transport into cell
- give antigenic specificity that is good for identification
What are the two teichoic acids in a gram-positive cell wall?
1. lipoteichoic acids (anchored in plasma membrane)
2. wall teichoic acids (bound to peptidoglycan layer)
Gram Negative Cell Wall
- outer membrane (OM) made of lipopolysaccharide (LPS), lipoproteins, porins, and phospholipids (lipid bilayer)
- thin layer of peptidoglycan
- no teichoic acids
- gel-like fluid between outer membrane and plasma membrane
- contains enzymes and transport proteins
What is the outer membrane composed of in a gram negative cell wall?
- lipopolysaccharide (LPS)
Outer Membrane of Gram Negative Cell Wall
- strong negative charge helps resist phagocytosis
- barrier to certain antibiotics (e.g., penicillin), digestive enzymes (e.g., lysozyme), detergents, heavy metals, bile salts, and certain dyes
Lipoproteins of Gram Negative Cell Wall
- lipids covalently bonded to proteins
- function as anchor between OM and peptidoglycan
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