VIRUSES, VIROIDS, AND PRIONS Flashcards
are very tiny organisms that
can cause diseases in living things.
viruses
key components of virus
capsid, envelope, genome
general characteristics of virus
genetic material
host dependency
diverse shapes
or protein shell, of a virus
is made up of many protein molecules.
capsid
These capsids are
named after their
linear, thin, thread-like
appearance. They
called rod-shaped or
helical.
helical
have twenty faces, and
are named after the
twenty-sided shape
called an icosahedron.
icosahedral
These capsids are kind of a
hybrid between the helical and
icosahedral shapes. They
basically consist of an
icosahedral head attached to a
helical tail.
complex
A lipid bilayer that surrounds
some viruses, derived from the
host cell’s membrane.
viral envelope
s are infectious pathogens that
affect only plants, therefore are also
called plant pathogens.
viroids
general charcteristics of viroids
infectious rna molecules, no protein encoded, transmission via seeds
It refers to abnormal, pathogenic
agents that are transmissible and are
able to induce abnormal folding of
specific normal cellular proteins
prions
general characteristics of prions
proteinaceous, infectious
These prion proteins are found on the cell membrane and play
an important role in cell signalling and cell adhesion. More
research is being carried out to discover its functions.
PrPc
This is the disease-causing prion and is resistant to proteases. It
affects the confirmation of PrPc and changes it. They are
believed to have more beta sheets than the alpha helices.
PrPsc
the bacteriophage takes
over the cell, reproduces new
phages, and destroys the cell
lytic cyle
the phage genome
integrates into the bacterial
chromosome and becomes part of
the host.
lysogenic cycle
the first
stage in the infection process in which
the phage interacts with specific
bacterial surface receptors.
attachments
This occurs through contraction of the tail sheath, which acts like a hypodermic
needle to inject the viral genome
through the cell wall and membrane.
The phage head and remaining
components remain outside the
bacteria
penetration
After entering the host cell, the virus
synthesizes virus-encoded endonucleases to degrade the
bacterial chromosome.
biosynthesis
new virions are created. To liberate free phages, the bacterial cell wall is disrupted by phage
proteins such as holin or lysozyme.
maturation
Mature viruses burst out of the host cell
in a process called lysis and the progeny viruses are liberated into the environment to infect new
cells
release
lytic cycle
attachment, penetration, biosynthesis, maturation, release
life cycle of viruses with animal hosts
attachment, penetration, uncoating, biosynthesis, assembly, release
It occurs when a virus is not completely cleared from the system of the host but stays in certain tissues or organs of the infected person.
persistent infections
