TRAIT
Method of
reproduction?
VIRUS
 Viruses need the host cell in order to
reproduce
 Glycoproteins on the viral envelope of
animal viruses promotes entry into the
host
 Phages reproduce either through the
lytic or lysogenic cycle
Type of nucleic acid?  Contains either DNA or RNA, but
never both
 Usually RNA
 Can be single-stranded or doublestranded
Outer layer?
 Capsid (protein shell) determines the
shape of the virus, and protects the
viral genome
 Some viruses have viral envelopes,
(may be derived from host cell
membrane); helps facilitate entry into
host cell; glycoproteins from virus,
phospholipids from host
Independent
 CANNOT EXIST ON ITS OWN
existence?
 Lacks ability to make proteins,
reproduce, store/generate energy
 Needs host cell
Ability to generate
 Cannot store energy (ATP)
own energy?
 Must derive energy from host cell
 No metabolic functions either
Size?
 Much smaller than prokaryotic and
eukaryotic cells
 Tiniest are only 20 nm in diameter,
which is smaller than a ribosome!
Can they make their
own proteins?
 CANNOT SYNTHESIZE OWN
PROTEINS! Lacks ribosomes!
 Uses ribosomes of host cell to
translate viral messenger RNA into
viral proteins
CELL
 Eukaryotic cells go through the cell
cycle, which includes mitosis,
cytokinesis, etc.
 Prokaryotic cells go through a much
simpler process, binary fission
 Both generate identical daughter
cells
 CAN REPRODUCE ON ITS OWN
 DNA
 Phospholipid bilayer with proteins
makes up the plasma membrane
 Plant cells and prokaryotic cells
also have cell walls made of
cellulose
 Prokaryotic cells may have a
capsule (jellylike coating) on the
outside
 Can exist as one cell; for example,
Paramecium
 Cellular respiration!
 ATP!
 Able to harvest chemical energy
 Prokaryotic cells are much smaller
than eukaryotic cells, but still much
bigger than viruses
 Diameters range from 1-100
micrometers
 Ribosomes used for protein
synthesis