General Characteristics of Viruses- Microbiology |ICDS Supervisor Exam Kerala PSC
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General Characteristics of Viruses |
General Characteristics of Viruses
The word virus, the Latin word for poison.
Viral Size
Viruses range from 20 to 1000 nm in length.
Different viruses vary
considerably in size.
Although most are quite a bit smaller than
bacteria, some of the larger viruses.
For Example: Adenovirus 90 nm
, Poliovirus 30 nm
General properties
Viruses are inert/crystaline outside the body of host as soon as they
come into the host they become living.
They are obligatory
intracellular parasites that is, they absolutely require livinghost cells
in order to multiply.
The truly distinctive features of viruses are.
- Contain a protein coat (sometimes itself enclosed by an
envelope of lipids, proteins, and carbohydrates) that surrounds
the nucleic acid.
- Multiply inside living cells by using the synthesizing machinery
of the cell.
-Cause the synthesis of specialized structures that can transfer
the viral Contain a single type of nucleic acid, either DNA or
RNA.
- nucleic acid to other cells.
-Viruses have few or no enzymes of their own for metabolism; for
example, they lack enzymes for protein synthesis and ATP
generation.
To multiply, viruses must take over the metabolic
machinery of the host cell.
Viruses are Host Specific
There
are viruses that infect
invertebrates, vertebrates,
plants, protists, fungi, and
bacteria.
However, most viruses
are able to infect specific types
of cells of only one host species.
In rare cases, viruses cross the
host-range barrier, thus
expanding their host range.
The particular host range of a virus is
determined by the virus’s requirements for its specific attachment to
the host cell and the availability within the potential host of cellular
factors required for viral multiplication.
For the virus to infect the
host cell, the outer surface of the virus must chemically interact with
specific receptor sites on the surface of the cell.
Viral Structure
Viruses may be Hexagonal, Octagonal or have any other shape and
have a 3D structure a virion is a complete, fully developed,
infectious viral particle composed of nucleic acid and surrounded by
a protein coat outside of a host cell, and is a vehicle of transmission
from one host cell to another.
Nucleic Acid
A virus can have either DNA or RNA—but never both. The nucleic
acid of a virus can be single-stranded or double-stranded.
There are viruses with the familiar:
- double-stranded DNA
x single-stranded DNA
x double-stranded RNA
x single-stranded RNA
Depending on the virus, the nucleic acid can be linear or circular.
In
some viruses (such as the influenza virus) the nucleic acid is in
several separate segments.
Capsid and Envelope
The nucleic acid of a virus is protected by a protein coat called the
capsid.
Each capsid is composed of protein subunits called
capsomeres.
In some viruses, the proteins composing the
capsomeres are of a single type; in other viruses, several types of
protein may be present. a particular type of virus.
In some viruses,
the capsid is covered by an envelope which usually consists of some
combination of lipids, proteins, and carbohydrates., that is derived
from the host cell membrane.
Some viruses are not covered by an
envelope are known as Naked Virus/non-enveloped viruses.
The
capsid of a non-enveloped virus protects the nucleic acid from
nuclease enzymes in biological fluids and promotes the virus’s
attachment to susceptible host cells.
Depending on the virus, envelopes may or may not be covered
by spikes, which are carbohydrate-protein complexes that project
from the surface of the envelope.
Some viruses attach to host cells
by means of spikes. Spikes are such a reliable characteristic of some
viruses that they can be used as a means of identification.
The ability
of certain viruses, such as the influenza virus to clump red blood cells
is associated with spikes.
Such viruses bind to red blood cells and
form bridges between them. The resulting clumping is called
hemagglutination.
Also Read;
Morphology of Bacteria
Anatomy of Bacteria
Vaccination -Types
This topic is important for the ICDS Supervisor Exam.Click HERE.
You can Go to more posts Regarding ICDS Supervisor Kerala PSC Here.
More ICDS Supervisor Kerala PSCSociology Notes Here
ICDS Supervisor Kerala PSC Homescience Notes Here
Microbiology Notes
ICDS Supervisor Kerala PSC Food ,Nutrition and Health Notes Here
Also Read;
Morphology of Bacteria
Anatomy of Bacteria
Vaccination -Types
This topic is important for the ICDS Supervisor Exam.Click HERE.
You can Go to more posts Regarding ICDS Supervisor Kerala PSC Here.
More ICDS Supervisor Kerala PSCSociology Notes Here
ICDS Supervisor Kerala PSC Homescience Notes Here
Microbiology Notes
ICDS Supervisor Kerala PSC Food ,Nutrition and Health Notes Here
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