prokaryotes -
small, "simple" cells that typically have a cell wall and cytoplasmic membrane surrounding their cytoplasm, which contains ribosomes and a nucleoid comprised of one or more chromosomes with DNA genes, but have no membrane surrounding their nucleoid
eukaryotes -
large, "complex" cells with a nucleus that contains multiple chromosomes (with DNA genes) surrounded by a membrane plus a cytoplasm containing ribosomes and membrane-bound organelles, such as mitochondria, endoplasmic reticulum, vacuoles, chloroplasts (plants only), Golgi bodies
viruses -
acellular (not cells) nonliving entities, made up of genetic material (DNA or RNA) enclosed in a protein coat (many also have a membrane called an envelope), which can reproduce themselves only by infecting cells and utilizing cellular materials and processes
morphology -
these prokaryotes are
typically ~0.2-2 x 1-5 um and may be cylindrical (bacilli), spherical (cocci),
helical (spirilla or spirochetes)
or polymorphic (many shaped or amorphous)
cell
wall - rigid structure (peptidoglycan +/- lipopolysaccharide) that protects
against osmotic pressure damage and provides cell shape - cylindrical (bacillus);
spherical (coccus); helical (spirillum)
cytoplasmic
membrane - this lipid/protein outer boundary of the cytoplasm regulates what
goes in and out of the cell (permeability)
ribosomes -
small RNA/protein particles required for protein synthesis
chromosome -
large single strand of DNA that contains the "blueprint" for all cell structure and activity
in regions called genes
plasmids -
DNA that contains only a few genes and is exchanged between bacteria (codes for antibiotic
resistance or virulence factors)
salts - no special requirements; pathogenic fungi grow well at salt
concentrations found in the human body
importance and habitat - mostly decomposers (saprophytes), but some are pathogens; prefer dark,
moist habitats containing organic material
Protozoa
morphology - these unicellular eukaryotes have
larger cells (10-100 um) than fungi or bacteria
cytoplasmic
membrane - this lipid/protein outer boundary of the cytoplasm regulates what
goes in and out of the cell (permeability)
cell wall - none, but many for a pellicle just "inside" the cytoplasmic
membrane
contractile
vacuoles - regulate osmotic pressure by water expulsion
ribosomes -
small RNA/protein particles required for protein synthesis
chromosomes -
multiple DNA-containing structures that contain the "blueprint" for all cell structure
and activity in regions called genes
pseudopodia or undilipodia (cilia, flagella)
provide motility
cyst - dormant form; protects against adverse conditions
growth - process of cell enlargement and proliferation (increase in number)
proliferate by:
binary fission - division of a cell into two cells of equal size
and composition
budding - division of a cell into two cells of unequal size, but
equivalent composition
zygote formation - during mating, gametes fuse to form a zygote, which develops
into a egg, then (when conditions are "right") matures to form offspring
nutritional requirements
chemical - they derive their energy and nutrition from organic compounds
that they digest intracellularly (holozoic) or from organic compounds that they
digest extracellularly using enzymes they secrete (saprozoic)
water - living biological entities are typically ~70% water
essential elements - C (carbon), H (hydrogen), O (oxygen), N (nitrogen),
P (phosphorus), S (sulfur)
trace elements - Ca (calcium), Mg (magnesium), Fe (iron), Na (sodium),
K (potassium), Zn (zinc), Co (cobalt), Mn (manganese), plus others
organic growth factors - vitamins and other essential organic nutrients
physical
temperature - pathogenic protozoa grow best between 20C and 40C
(human body temperature is 37C)
oxygen - most are aerobic, but some are anaerobic
pH - most infectious protozoa "prefer"
near-neutral conditions pH ~6-8
salts - no special requirements; pathogenic protozoa grow well at
salt concentrations found in the human body
importance and habitat - free-living protozoa (moist environments) are a basic part
of food chains and webs; parasites are major causes of infectious disease in
humans and other animals
Helminths
morphology
multicellular eukaryotes which
possess organs and organ systems made up of tissues that are made up of cells,
which have these characteristics:
cytoplasmic
membrane - this lipid/protein outer boundary of the cytoplasm regulates
what goes in and out of the cell (permeability)
cell wall - none
ribosomes -
small RNA/protein particles required for protein synthesis
chromosomes -
multiple DNA-containing structures that contain the "blueprint" for all cell structure
and activity in regions called genes
flatwormsvs.roundworms:
flatworms have flattened bodies that are:
slender and broadly leaflike flukes (Trematodes),
which are microscopic
long and ribbonlike tapeworms (Cestodes),
some of which may be 10 meters long
roundworms (Nematodes)
have round
elongated bodies and range in size from microscopic to several centimeters in
length
holdfasts (hooks,
suckers, etc.) attach parasitic forms to host tissues (adhesins)
growth - process of cell enlargement and proliferation (increase in number)
proliferate by:
zygote formation - mating leads to fertilized eggs (ova) which are released
into the environment, to mature into offspring; Cestodes and Trematodes are
generally hermaphroditic (one worm possesses both male and female reproductive
organs)
many have complicated life-cycles requiring more than one host
nutritional requirements
chemical - they derive their energy and nutrition from organic compounds
(roundworms ingest food, whereas flatworms absorb nutrients
water - living biological entities are typically ~70% water
essential elements - C (carbon), H (hydrogen), O (oxygen), N (nitrogen),
P (phosphorus), S (sulfur)
trace elements - Ca (calcium), Mg (magnesium), Fe (iron), Na (sodium),
K (potassium), Zn (zinc), Co (cobalt), Mn (manganese), plus others
organic growth factors - vitamins and other essential organic nutrients
physical
temperature - pathogenic helminths grow best between 20C and 40C
(human body temperature is 37C)
oxygen - aerobic (no known anaerobes)
pH - most infectious helminths "prefer"
near-neutral conditions pH ~6-8
salts - no special requirements; pathogenic helminths grow well
at salt concentrations found in the human body
importance and habitat - decomposers are found everywhere (especially
roundworms); parasitic forms cause disease in plants or animals
Viruses
morphology -
very small (10 nm to 0.2 um)
nucleocapsid
nucleic acid - viral genes are made up of either DNA or RNA
capsid - protein coat made up of subunits called capsomeres
envelope - (optional) membrane "stolen" from host cell
growth -
they do not grow; they proliferate, but only inside host cells (viruses
are obligate intracellular parasites) by a process called replication,
which includes these steps:
attachment - to receptor sites on host cell by spikes
(peplomers)
penetration - entrance into host cell
uncoating - removal of capsid(s); frees the viral genes
to be expressed
synthesis - formation of viral DNA or RNA and proteins
assembly - components assemble to form viral nucleocapsids
release - viral particles (virions) "emerge" from the
host cell by lysis or "budding"
importance and habitat - pathogenic; ubiquitous, function
only in living cells