Ch. 4 Functional Anatomy of Prokaryotic and Eukaryotic Cells Flashcards
Prokaryote
comes from the Greek words for prenucleus
Eukaryote
comes from the Greek words for true nucleus
Avg. size of bacterial cells
0.2 to 2.0 micro meters x 2 to 8 micro meter length
Most bacteria are
monomorphic ( single shape)
a few bacteria are
pleomorphic (many shapes)
Bacillus
rod shaped
coccus
spherical shape
Spiral
-Vibrio
-Spirillum
-Spirochete
Star-shaped
Rectangular
Pairs
diplococci, diplobacilli
Clusters
staphylococci
Chains
Streptococci, streptobacilli
groups of four
tetrads
cubelike groups of eight
sarcinae
Scientific name
Bacillus (Bold)
Shape
bacillus
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 - Contribute to virulence
– Capsules prevent phagocytosis
– Extracellular polymeric substance helps form biofilms
Flagella
- Filamentous appendages external of the cell
- Propel bacteria
- Made of protein flagellin
Three parts of Flagella
– 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
Taxis
Flagella allow bacteria to move toward or away from stimuli
Flagella rotate
to “run” or “tumble”
Archaella
- Archaeal motility structure
- Made of glycoproteins archaellins
- Anchored to the cell
- Archaella (singular: archlaellum) rotate like flagella
Axial Filaments
- Also called endoflagella
- Found in spirochetes
- Anchored at one end of a cell
- Rotation causes cell to move like a corkscrew
Fimbriae
hairlike appendages that allow for attachment
Pili
– Involved in motility (gliding and twitching motility)
– Conjugation pili involved in DNA transfer from one
cell to another
The cell wall
- Prevents osmotic lysis and protects the cell membrane
- Made of peptidoglycan (in bacteria)
- Contributes to pathogenicity
Composition and Characteristics
- Peptidoglycan
– Polymer of a repeating disaccharide in rows:
▪ N-acetylglucosamine(NAG)
▪ N-acetylmuramicacid (NAM) - Rows are linked by polypeptides
Gram-Positive Cell Walls
-Thick peptidoglycan
-Teichoic acids
Gram-Negative Cell Walls
-Thin peptidoglycan
-Outer membrane
-Periplasmic space
Teichoic acids
– 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 antigen specificity
Periplasm between the outer membrane and the plasma membrane contains
peptidoglycan
Outer membrane made of
polysaccharides, lipoproteins, and phospholipids
Gram-neg cell walls protect from
phagocytes, complement, and antibiotics
gram-neg cell walls are made of
lipopolysaccharide (LPS)
— 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
Cell walls and the gram stain mechanism
- Crystal violet-iodine crystals form inside cell
- Gram-positive
– Alcohol dehydrates peptidoglycan
– CV-I crystals do not leave - Gram-negative
– Alcohol dissolves outer membrane and leaves holes
in peptidoglycan
– CV-I washes out; cells are colorless
– Safranin added to stain cells
Gram-Positive Cell Walls
- 2 rings in basal body of flagella
- Produce exotoxins
- High susceptibility to penicillin
- Disrupted by lysozyme
Gram-Negative Cell Walls
- 4 rings in basal body of flagella
- Produce endotoxins and exotoxins
- Low susceptibility to penicillin
Acid-fast cell walls
– Like gram-positive cell walls
– Waxy lipid (mycolic acid) bound to peptidoglycan
– Mycobacterium
– Nocardia
– Stain with carbolfuchsin
Mycoplasmas
-lack cell walls
-sterols in plasma membrane
Archaea
- Wall-less
- Walls of pseudomurein (lack NAM and D-aminoacids)
Lysozyme hydrolyzes bonds
in peptidoglycan
Penicillin inhibits
peptide bridges in peptidoglycan
Protoplast
a wall-less gram-positive cell
Spheroplast
a wall-less gram-negative cell
- protoplast and spheroplasts are susceptible to osmotic lysis
L forms
wall-less cells that swell into irregular shapes
The Plasma (cytoplasmic) Membrane
- Phospholipid bilayer that encloses the cytoplasm
- Peripheral proteins on the membrane surface
- Integral and transmembrane proteins penetrate the
membrane
Fluid mosaic model
– Membrane is as viscous as olive oil
– Proteins move freely for various functions
– Phospholipids rotate and move laterally
– Self-sealing
Selective permeability
plasma membrane allows the passage of some molecules, nut not others
Chromatophores
photosynthetic pigments on foldings
Functions
- Damage to the membrane by alcohols, quaternary
ammonium (detergents), and polymyxin antibiotics
causes leakage of cell contents - Contains enzymes for ATP production
Passive Processes:
substances move from high concentration to low concentration; no energy required
Active processes:
substances move from low conc. to high conc.;energy expended
Simple diffusion
movement of a solute form an area of high concentration to an area of low concentration
*Continue until molecules reach equilibrium
Facilitated diffusion
solutes combines with a transporter protein in the membrane
*Transports ions and larger molecules across a membrane with the conc. gradient
Facilitated diffusion
solute combines with a transporter protein in the membrane
*Transports ion and larger molecules across a membrane with the conc. gradient
Osmosis
the movement of water across a selectively permeable membrane from an area of high water to an area of lower water conc.
- through lipid layer
*Aquaporins (water channels)
Osmotic pressure
the pressure needed to stop the movement of water across the membrane
Isotonic solution
solute concentrations equal inside and outside of cell; water is at equilibrium
Hypotonic solution
solute conc. is lower outside than inside the cell: water moves into cell
Hypertonic solution
solute conc. is higher outside of cell than inside; water moves out of the cell
Active transport
requires a transporter protein and ATP; goes against gradient
Group translocation
requires a transporter protein and phosphoenolpyuvic acid (PEP); substance is altered as it crosses the membrane
Cytoplasm
- The substance inside the plasma membrane
- Eighty percent water plus proteins, carbohydrates, lipids,
and ions - Cytoskeleton
The Nucleoid
- Bacterial chromosome:
- Plasmids
Bacterial chromosome
circular thread of DNA that
contains the cell’s genetic information
Plasmids
extrachromosomal genetic elements; carry
non-crucial genes (gram ., antibiotic resistance, production of
toxins)
Ribosomes
- Sites of protein synthesis
- Made of protein and ribosomal RNA
- 70S
– 50S + 30S subunits
Metaphoric granules (volition)
phosphate reserves
Polysaccharide granules
energy reserves
Lipid inclusions
energy reserves
Sulfur granules
energy reserves
carboxysomes
RuBis CO enzyme for CO2 fixation during photosynthesis
Gas vacuoles
protein covered cylinders that maintain buoyancy
magentosomes
iron oxide inclusions; destroy H2O
Sporulation
endospore formation
Germination
endospore returns to vegetative state
Flagella
long projections: few in number
Cilia
short projections; numerous
Cell wall
- Found in plants, algae, and fungi
- Made of carbohydrates (cellulose plants, chitin-fungi, glucan, and mannan-yeasts)
Glycocalyx
-Carbohydrates bonded to proteins and lipids in the plasma membrane
- Found in animal cells
Endocytosis
phagocytosis and pinocytosis
phagocytosis
pseudopods extend and engulf particles
Pinocytosis
membrane folds inward, bringing in fluid and dissolved substances
Cytoplasm
substance inside the plasma and outside the nucleus
Cytosol
fluid portion of cytoplasm
Cytoskeleton
made of microfilaments and intermediate filaments; gives shape and support
Cytoplasmic streaming
movement of the cytoplasm throughout the cell
Nucleus
- double membrane structure (Nuclear envelope) that contains the cell’s DNA
-DNA is complexed with histone proteins to form chromatin
-During mitosis and meiosis, chromatin condenses into chromosomes
Rough ER
studded with ribosomes; sites of protein synthesis
smooth ER
no ribosomes; synthesizes cell membranes, fats, and hormones
Golgi complex
- transport organelle
- modifies proteins from the ER
- Transports modified proteins via SECRETORY VESICLES to the plasma membrane
Lysosomes
-vesicles formed in the Golgi complex
-contain digestive enzymes
Vacuoles
-cavities in the cell formed from the Golgi complex
- bring food into cells; provide shape and storage
Mitochondria
- double membrane
-contain inner folds (cristae) and fluid (matrix)
-involved in cellular respiration (ATP production)
Chloroplasts
-locations of photosynthesis
-contain flattened membranes (thylakoids) that contain chlorophyll
Peroxisomes
oxidize fatty acids; destroy H2O2
Centrosomes
-network of protein fibers and centrioles
-form the mitotic spindle; critical role in cell division
life arose as simple organisms ___ to _ billion _____ ago
3.5, 4, years
First eukaryotes evolved ___ billion years ago
2.5
Endosymbiotic theory
-larger bacterial cells engulfed smaller bacterial cells, developing the first eukaryotes
- ingested photosynthetic bacteria becomes chloroplasts
- ingested aerobic bacteria became mitochondria
