Transcript Size and Shape of Viruses

Viruses
What do you think this is?
What do you Think These Objects
are? Are They Living?
Prion, Virus, and Viroid
Viroid – pathogen causes disease in a
plant. Protein but no capsid - RNA
Prion – pathogen made only of a protein.
Mutates your proteins! No DNA OR RNA
2. Plant Viruses(viroids)
First plant virus to be identified
was the tobaccomosaic virus
400 viruses that infect plants,
causing as many as 1000
diseases
Can be beneficial - flower
color,
Plant Virus Tobacco Mosiac
3. Prions:
Particles composed of proteins
and have no nucleic acids (still
infectious)
Influence how proteins fold into
their active shape
Example: Mad cow disease
(destroys brain damage).
Prions(cause mutations in
chromosomes or proteins)
Alzheimer's disease
Creutzfeldt-Jakob disease
Down's syndrome
Fatal familial insomnia
Gerstmann-Straussler syndrome
Kuru Leprosy
Prion crystalline protein structure
Viroids
So small; No real pictures!
Viroids Hepatitis D
Bacteria Vs Virus
VIRUSES
Virus: infectious particle that contains DNA or
RNA surrounded by a protein coat that can only
reproduce in a host cell.
Latin for “poison”.
Bacteriophage attacking a bacteria!
History of viruses
Martinus Beijerinck: Dutch scientist who said that
disease is caused by tiny particles in juice.
Called them viruses. Latin for poison.
Wendall Stanley: isolated crystals of the tobacco
mosic virus.
Dmitri Ivanovski: for tobacco mosiac in liquids
extracted from infected plants.
Are viruses alive? Scientists are still
arguing!!!
At the boundary of life, between the macromolecules
(which are not alive) and the prokaryotic cells (which
are), lie the viruses and bacteriophages (phages).
These twilight creatures are parasites responsible for
causing many diseases in living things (herpes and
HIV in humans, for example).
Viruses are found everywhere.
In isolation, viruses and
bacteriophages show
none of the expected
signs of life. They do not
respond to stimuli, they
do not grow, they do not
do any of the things we
normally associate with
life.
Characteristics of Living Things
Respond to stimulus: virus respond when a cell is
near and attaches.
Cells: Not cells as we know them
Adapt: The viruses do mutate to become stronger but
only in a host cell.
Reproduces: only in a host cell
Energy: Uses energy of the host
DNA: Yes they do have their own
Grow and develops: Only in host
Viruses are parasites that can only perform certain
characteristics in host cells.
Host: The cell that the virus attaches and uses their
DNA and resources.
How do They Name Viruses
1. After the disease they cause.
2. After the organ or tissue they attack
3. Today, they are given a genus name
ending in the word virus. Code numbers
are given to similar viruses
PARTS OF A VIRUS
Viruses consist of a core of nucleic acid,
either DNA or RNA, and a protective coat of
protein molecules and sometimes
lipids(capsid).
CAPSID: Protein coat
Surrounding the DNA.
Why is Capsid Important?
It is the protein coat around the virus that
protests its DNA or RNA.
IT IS WAY THEY ARE SO HARD TO KILL!!!!!!
How Do Viruses Attack Their
Host
Host - Cell the virus attacks.
Attaches to the host cell and interlocks
with the protein of the host cell.
Viruses are very specific to the cells
they attack. This helps in the spread
of the disease.
The outside envelope matches the cell
that it attacks. Viruses are specific!
Attacking Host
The virus will attach itself to the host cell. It will then shoot
its DNA into the host cell. The virus is a parasite that uses
the host cell for its energy and reproduction. It is a little
different if it is a bacteria cell or eukaryotic cell.
Attacking the host
The size and shape of a virus determines which
cells or host they can attack.
Virus Attached to Host
Size and Shape of Viruses
Viruses come in all shapes sizes. You can only
see them with a microscope.
3 shapes of viruses
1.Enveloped – round with spikes( flu viruses)
2.Helical – Long narrow coiled shape( rabies)
3.Polyhedral- many sides(foot and mouth disease)
The different proteins that make up the
capsid determines the shape of the virus.
Difference between a bacteriophage and a
virus
Bacteriophages attack bacteria (prokaryotes)
viruses attack eukaryotic cells(have a nucleus).
Viruses and bacteriophages invade cells and use the
host cell's machinery to synthesize more of their own
macromolecules.
Once inside the host the bacteriophage or virus
will either go into a Lytic Cycle destroying the host cell during
reproduction.
or
It will go into a Lysogenic Cycle - a
parasitic type of partnership with the cell
Lytic Cycle
In the lytic cycle, the virus takes over the hosts DNA and
grows its own. It grows its own DNA and new viruses.
The virus uses the energy of the host cell. When it is full,
the host cell explodes and releases new viruses.
Lysogenic Cycle
The virus COMBINES its DNA with the host DNA producing a
Prophage. The cell is not destroyed. As new cells are made, it
will be the virus and not host cell. Cell not destroyed.
The Lytic Cycle
The Lysogenic Cycle
4 types of Viruses
Retroviruses
Viruses that contain RNA as their nucleic acid
Once inside a host cell, the retrovirus makes DNA
from its RNA
Use reverse transcriptase (enzyme) to do thislocated inside capsid
The double-stranded DNA is then inserted into
the host cell’s chromosome and becomes a
provirus
Example: HIV (Human Immunodeficiency Virus)
infects white blood cells, which are used in
fighting off infections and disease
A retrovirus injects the enzyme, reverse transcriptase into the cell
to copy viral RNA into DNA.
HIV Virus
HIV is a retrovirus injecting the enzyme, reverse
transcriptase into the cell to copy viral RNA into DNA.
HIV doesn’t target just any cell, it goes right for the cells that
want to kill it. “Helper" T cells are HIV's primary target. These
cells help direct the immune system's response to various
pathogens.
HIV undermines the body's ability to
protect against disease by depleting T
cells thus destroying the immune system.
The virus can infect 10 billion cells a day,
yet only 1.8 billion can be replaced daily.
After many years of a constant battle, the body
has insufficient numbers of T-Cells to mount an
immune response against infections. At the point
when the body is unable to fight off infections, a
person is said to have the disease AIDS.
It is not the virus or the disease that ultimately
kills a person; it is the inability to fight off
something as minor as the common cold.
Viruses are host specific – a protein on the surface of the virus
has a shape that matches a molecule in the plasma membrane
of its host, allowing the virus to lock onto the host cell.
How Do Vaccines Work
A vaccine contains a killed or weakened part of a
germ that is responsible for infection. Because the
germ has been killed or weakened before it is used
to make the vaccine, it can not make the person
sick. When a person receives a vaccine, the body
reacts by making protective substances called
"antibodies". The antibodies are the body's
defenders because they help to kill off the germs
that enter the body. In other words, vaccines
expose people safely to germs, so that they can
become protected from a disease but not come
down with the disease.
Jenner was operating on the now widely
accepted principle that once a person catches
a certain disease, he or she is immune to it for
the rest of their life. For example, once you've
had the chickenpox, it's extremely unlikely that
you'll ever catch it again. This is because your
body, when exposed again, will recognize the
disease and fight it off. The beauty of vaccines
is that they help the body develop diseasefighting abilities without making you sick.
Vaccines accomplish this amazing feat by
tricking the body into believing it already has
the full-blown disease. Here are the steps in
this process, known as the "immune
Vaccine-preventable Diseases
Anthrax
Cervical Cancer
Diphtheria
Hepatitis A
Hepatitis B
Haemophilus influenzae type b
Human Papillomavirus
Influenza
Japanese encephalitis
Lyme disease
Measles
Meningococcal
Monkey pox
Mumps
Pneumococcal
Polio
Rabies
Rotavirus
Rubella
Shingles
Smallpox
Tetanus
Typhoid
Tuberculosis
Varicella
Yellow Fever
Common Cold
Swine Flu
Bird Flu
Bacteria
1.Organelles
2.Kill with antibiotic
3.Reproduces on own
4.Needs energy
5. Cell
6.Responds
7.Adapts
8.Grows
Virus
DNA
Reproduces
Energy from
host
Mutates
hard to kill
Capsid