ULTRASTRUCTURE Flashcards
Prokaryotes characteristics (8)
Ave 1-2 um in dia.
* No nucleus
* No membrane-bound organelles
* Circular, Naked DNA (nucleiod)
* Divides by fission
* Cytoskeletons absent
* Not capable of endocytosis & exocytosis
* 70S ribosomes
Prokaryotes examples
bacteria,archaea, cyanobacteria
(BGA), mycoplasmas
Eukaryotic characteristics (8)
- > 10-100 um
- With nucleus
- With membrane-bound organelles
- Packed in chromosomes
- Divides by mitosis & meiosis
- w/ cytoskeleton
- Capable of endocytosis &
exocytosis - 80S ribosomes
Eukaryotic examples (4)
yeasts, molds, algae, protozoa
Thin hairlike filament with helical shape extending from the
cytoplasmic membrane and cell wall
Flagella
Filament protein of flagella is called
Flagellin, hook, basal body
Flagella propel through liquid as fast as
100um/sec = 3000 body lengths
per minute
Flagella rotates in what fashion
corkscrewlike-fashion
Function of flagella
Motility
Chemotaxis
responses to other environmental stimuli
Chemotaxis
Arrangements of flagella and explain
Mono,Lipo,Amphi,Perittrichous
-also called fimbriae
- filamentous, hollow-like but not helical
Pilus/Pili
Pili/fimbriae found in
Gram negative bacteria
Function of Pili
for sexual reproduction, attachment or adhesion
layer of viscous material composed of polymers
- Require special stains for microscopic observations = appear as halo
Glycocalyx
2 types of glycocalyx and function
Capsule- firmly attached
Slime- loosely attached
Function of glycocalyx (4)
- adherence
- reservoir of stored food
- prevent attachment and lysis of cells by bacteriophages
- protect bacteria from phagocytosis.
-Thick rigid layer surrounding the cytoplasmic membrane
Cell wall
Cell wall is composed of
peptidoglycan (a.k.a. murein) 10-40%
Function of cell wall (4)
- gives shape to bacterial cells (spherical, rod like, or
spiral) - reaction to gram stain (positive or negative).
- protection from differences in osmotic pressure
- involved in normal growth & cell division
3 kinds of building
blocks cell wall
1) N-acetylglucosamine
(NAG)
2) N-acetylmuramic acid
(NAM)
3) Tetrapeptide- amino acids may differ from
one bacterium to another
formed by
cross-linkage of one
polypeptide chain with
another through the
tetrapeptides
Rigid framework
Lipid A can be toxic in humans, and if so, is referred to as
Endotoxin
O polysaccharides functions as
Antigens
Also called cytoplasmic membrane
Plasma Membrane
the only eubacteria without cell wall;
contain sterols in the cytoplasmic membrane
Mycoplasma
Function of plasma membrane (4)
Functions:
1) Transport of molecules in & out of the cell
2) Site of enzyme specific activity
3) Site for energy production & synthesis of cell wall
4) Involved in DNA replication & cell division
appearance of mycoplasma colonies on agar. The
colonies are about 0.5 mm in diameter.
Fried egg
Prevents leakage and gateway for transport nutrients into and out of cell
Permeability Barrier
Site of proteins
Protein anchor
Site of generation and use of the proton motive force
Energy Conservation
Site of many chemical reactions
Thick fluid
Cytoplasm
Cytoplasm is 80% water and contains (5)
containing amino acids, lipids, carbohydrates,
ions, and enzymes
Suspends other substances in cytoplasm such as. (4)
ribosomes sulfur granules volutin granulespoly-β-hydroxybutyrate(PHB)
for protein synthesis
ribosomes
in H2S-oxidizing bacteria (as energy
source)
sulfur granules
used for identification including
causative agent of diphtheria
volutin granules
as reserve C & energy source
poly-β-hydroxybutyrate(PHB)
nuclear material positioned near the
center of the cell
* Naked DNA
* Circular chromosome
Nucleoid
Functions Nucleoid
- it stores the cell’s hereditary material,
or DNA - coordinates the cell’s activities, which
include growth, intermediary
metabolism, protein synthesis, and
reproduction (cell division).
-are circular extrachromosomal DNA
Plasmids
Dormant forms of bacteria
*Thick-walled highly refractile, highly resistant to
environmental changes
Spores/Endospores
from spore during sporulation resulting
in dehydration process
expulsion of water
not found in
vegetative cells
large amount of dipicolinic acid (DPA)
Heat resistance could be due to:
1) expulsion of water from spore during sporulation resulting
in dehydration process
2) large amount of dipicolinic acid (DPA) – not found in
vegetative cells
Pose problem in the food industry
Clostridium botulinum – causes botulism (type of food
poisoning)
Produced one per cell
*Highly resistant to extreme heat (w/stand 80°C for 10 min),
drying & exposure to chemicals
Spores/ Endospores
Examples of Genera that are endospore-forming:
Clostridium, Bacillus = bacilli- shaped (more common)
Sporosarcina = cocci- shaped (exception)
bright
refractile structures) inside
the cells
presence of
endospores
Formation of Endospores
Vegetative cell, Sporulating, Mature spore
widespread in
dairy products and some are potent
pathogens.
Streptococcus
bacilli
* palisade arrangement
Arthrobacter
Stalked-bacterium
* rossete formation
Caulobacter
