Anatomy of Prok and Euk Cells Flashcards
Briefly describe the functions of the flagella of a bacterial cell.
Flagella allow bacteria to move toward or away from stimuli (taxis)
Flagella rotate to “run” or “tumble”
Flagella proteins are H antigens and distinguish among serovars (e.g., Escherichia coli O157:H7)
Briefly describe the size and arrangement of bacterial cells.
- Average size: 0.2 to 2.0 μmeter diameter × 2 to 8 μmeter length
- Most bacteria are monomorphic (single shape)
- A few are pleomorphic (many shapes)
Briefly describe the possible arrangements of bacterial cells.
pairs: diplo-
clusters: staphylo-
chains: strepto-
fours: tetrads
cube/eights: sarcinae
Describe major features of the prokaryotic cell.
Prokaryote
* One circular chromosome, not in a membrane
* No histones
* No organelles
* Bacteria: peptidoglycan cell walls
* Archaea: pseudomurein cell walls
* Divides by binary fission
Briefly describe the physical form of the flagella of a bacterial cell.
Three parts:
Filament: outermost region
Hook: attaches to the filament
Basal body: consists of rod and pairs of rings; anchors flagellum to the cell wall and membrane
Briefly describe the model describing the cytoplasmic membrane.
Fluid mosaic model
Membrane is as viscous as olive oil
Proteins move freely for various functions
Phospholipids rotate and move laterally
Self-sealing
Describe major features of the eukaryotic cell.
Eukaryote
* Paired chromosomes, in nuclear membrane
* Histones
* Organelles
* Polysaccharide cell walls, when present
* Divides by mitosis
Briefly describe gram-positive cell walls.
thick peptidoglycan
has teichoic acids
Briefly describe the additional features of the gram-negative cell wall.
Protect from phagocytes, complement, and antibiotics
Made of lipopolysaccharide (L P S)
O polysaccharide functions as antigen (e.g.,
E. coli O157:H7)
Lipid A is an endotoxin embedded in the top layer
Porins (proteins) form channels through membrane
Briefly describe the cytoplasmic membrane.
Phospholipid bilayer that encloses the cytoplasm
Peripheral proteins on the membrane surface
Integral and transmembrane proteins penetrate the membrane
Briefly describe the cell walls of mycoplasmas.
atypical.
lack of cell walls
sterols in plasma membrane
Briefly describe axial filaments.
Also called endoflagella
Found in spirochetes
Anchored at one end of a cell
Rotation causes cell to move like a corkscrew
Briefly describe acid-fast cell walls.
Atypical cell wall
similar to gram-positive
waxy lipid (mycolic acid) bound to peptidoglycan
stain with carbolfuchisin
examples: mycobacterium, nocardia
Briefly describe fimbriae.
Hairlike appendages that allow for attachment.
Briefly describe the flagella of a bacterial cell.
Filamentous appendages external of the cell
Propel bacteria
Made of protein flagellin
Briefly describe the glycocalyx.
- External to the cell wall
- Viscous and gelatinous
- Made of polysaccharide and/or polypeptide
Two types:
* Capsule: neatly organized and firmly attached
* Slime layer: unorganized and loose
Briefly describe the effects of lysozyme on cell walls.
Lysozyme hydrolyzes bonds in peptidoglycan.
Briefly describe effects of penicillin on the cell wall.
Penicillin inhibits peptide bridges in peptidoglycan.
Briefly describe the functions of the cytoplasmic membrane.
The plasma membrane’s selective permeability allows the passage of some molecules, but not others
Contain enzymes for ATP production
Some membranes have photosynthetic pigments on foldings called chromatophores
Briefly describe the possible shapes of bacterial cells.
bacillus - rod-like
coccus - spherical
spiral (vibrio, spirillum, spirochete)
star-shaped
rectangular
Define Plasmids.
extrachromosomal genetic elements; carry non-crucial genes (antibiotic resistance, production of toxins)
Contrast some things between gram-positive and gram-negative cell walls.
Gram Positive
2 rings in basal body of flagella
Produce exotoxins
High susceptibility to penicillin
Disrupted by lysozyme
Gram Negative
4 rings in basal body of flagella
Produce endotoxins and exotoxins
Low susceptibility to penicillin
Briefly describe the purpose of the cell wall in bacteria.
Prevents osmotic lysis and protects the cell membrane.
Contributes to pathogenicity.
Define Bacterial chromosome
circular thread of DNA that contains the cell’s genetic information
Contrast flagella and cilia.
Projections used for locomotion or moving substances along the cell surface
Flagella-long projections; few in number
Cilia-short projections; numerous
Both consist of microtubules made of the protein tubulin
Microtubules are organized as 9 pairs in a ring, plus 2 microtubules in the center (9 + 2 array)
Allow flagella to move in a wavelike manner
List and describe some inclusions.
Metachromatic granules (volutin)-phosphate reserves
Polysaccharide granules-energy reserves
Lipid inclusions-energy reserves
Sulfur granules-energy reserves
Carboxysomes-RuBis C O enzyme for CO2 fixation during photosynthesis
Gas vacuoles-protein-covered cylinders that maintain buoyancy
Magnetosomes-iron oxide inclusions; destroy H2O2
Briefly describe endospores, sporulation, and germination.
Resting cells; produced when nutrients are depleted
Resistant to desiccation, heat, chemicals, and radiation
Produced by Bacillus and Clostridium
Sporulation: endospore formation
Germination: endospore returns to vegetative state
Briefly describe the membranes of gram-negative cell walls.
Periplasm between the outer membrane and the plasma membrane contains peptidoglycan
Outer membrane made of polysaccharides, lipoproteins, and phospholipids
Briefly describe how the glycocalyx contributes to virulence.
Contribute to virulence
* Capsules prevent phagocytosis
* Extracellular polymeric substance helps form biofilms
Briefly describe gram-negative cell walls.
thin peptidoglycan
has outer membrane
has periplasmic space
Porins (proteins) form channels through membrane
What are L forms?
L forms are wall-less cells that swell into irregular shapes.
Briefly describe pili.
Involved in motility (gliding, twitching).
Conjugation pili involved in DNA transfer between cells.
Briefly describe the composition of bacterial cell walls.
Peptidoglycan
Polymer of a repeating disaccharide in rows:
N-acetylglucosamine( N A G)
N-acetylmuramicacid (N A M)
Rows are linked by polypeptides
Briefly describe teichoic acids.
Found in gram-positive cell walls.
Lipoteichoic acid links cell wall to plasma membrane
Wall teichoic acid links the peptidoglycan
Carry a negative charge
Regulate movement of cations
Polysaccharides and teichoic acids provide antigenic specificity
Briefly describe the archaella of motile archaeal cells.
Archaeal motility structure
Made of glycoproteins archaellins
Anchored to the cell
Archaella (singular: archlaellum) rotate like flagella
Briefly describe the cell walls of archaea.
atypical.
wall-less, or
walls of pseudomurein
(and lack NAM, D-amino acids)
