1 viruses. 2 are viruses living or non-living? viruses are non living they have some properties of...
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Viruses
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Are Viruses Living or Are Viruses Living or Non-living?Non-living?
Viruses are non livingThey have some properties of
life but not othersThey can’t maintain a constant
internal state (homeostasis) or reproduce without a host cell.
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What are What are Viruses?Viruses?
A virus is a non-cellular particle made up of a nucleic acid and protein coat (capsid) that can invade living cells.
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SmallpoxSmallpoxEdward Jenner
(1796) developed a smallpox vaccine using milder cowpox viruses
Deadly viruses are said to be virulent
Smallpox has been eradicated in the world today
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Viewing VirusesViewing Viruses
Viruses are Viruses are smaller than the smaller than the smallest cellsmallest cell
Viruses Viruses couldn’t be seen couldn’t be seen until the until the electron electron microscopemicroscope was was invented in the invented in the 2020thth century century
What is a Nanometer?
A nanometer is a unit of measure. Just like inches, feet and miles. By definition a nanometer is one-billionth of a meter. A meter is about 39 inches long. That is a big number and when you divide a meter into one billion pieces, well that is very small.
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Size of VirusesSize of Viruses
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Viral Viral StructureStructure
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CharacteristicsCharacteristicsNon living NoncellularContain: 1. a protein coat called the
capsid 2. nucleic acid core
containing DNA or RNACapable of reproducing only
when inside a HOST cell
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CharacteristicsCharacteristics
Some viruses are enclosed in an protective envelopeSome viruses may
have spikes to help attach to the host cellMost viruses infect
only SPECIFIC host cells
CAPSID
ENVELOPE
DNA
SPIKES
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CharacteristicsCharacteristics
Outside of host cells, viruses are inactive
Lack ribosomes and enzymes needed for metabolism
To be able to reproduce they use the raw materials and enzymes of the host.
EBOLA VIRUS
HIV VIRUS
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CharacteristicsCharacteristics
Some viruses cause disease
Smallpox, measles, mononucleosis, influenza, colds, warts, AIDS, Ebola
Some viruses may cause some cancers like leukemia MEASLES
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Viral ShapesViral Shapes
Viruses come in a variety of shapes
Some may be helical shape like the Ebola virus
Some may be polyhedral shapes like the influenza virus
Others have more complex shapes like bacteriophages
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Helical VirusesHelical Viruses
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Polyhedral VirusesPolyhedral Viruses
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Complex VirusesComplex Viruses
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Herpes VirusHerpes Virus
SIMPLEX I and II
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AdenovirusAdenovirus
COMMON COLD
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Influenza VirusInfluenza Virus
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Chickenpox VirusChickenpox Virus
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Papillomavirus – Papillomavirus – Warts!Warts!
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Bacteriophages
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PhagesPhages
Viruses that attack bacteria are called bacteriophage or just phage
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BacteriophageBacteriophage
They infect E. coli , an intestinal bacteria
Six small spikes at the base of a contractile tail are used to attach to the host cell
Viral DNA is injected into the host cell
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Escherichia coli Bacterium
T - EVEN PHAGES ATTACK THIS BACTERIUM
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Bacteriophages
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Retrovirus Retrovirus
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Characteristics of Characteristics of Retroviruses/LatentRetroviruses/Latent
Contain RNA, not DNAContain enzyme called
Reverse TranscriptaseWhen a retrovirus infects a
cell, it injects its RNA and reverse transcriptase enzyme into the cytoplasm of that cell and it is able to make DNA
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Retroviruses Retroviruses HIV, the
AIDS virus and human T cell leukemia virus are retroviruses
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Viral Viral ReplicationReplication
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Viral AttackViral Attack
Viruses are very specific as to which species they attackHOST specificHumans rarely share viral
diseases with other animalsEukaryotic viruses usually
have protective envelopes made from the host cell membrane
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BacteriophageBacteriophage Replication-Lytic CycleReplication-Lytic CycleBacteriopha
ge inject their nucleic acid
They lysis (break open) the bacterial cell when replication is finished
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Attachment Phage attaches by tail fibers to
host cell Entry Tail sheath contracts to
force tail core and DNA into cellReplication Production of phage DNA
and proteinsAssembly Assembly of phage particlesLysis/Release Phage breaks cell wall and releases new viruses
Lytic Cycle ReviewLytic Cycle Review
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Viral LatencyViral LatencySome viruses have the ability
to become dormant inside the cellCalled latent virusesThey may remain inactive for
long periods of time (years)Later, they activate to produce
new viruses in response to some external signal
HIV and Herpes viruses are examples
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Lysogenic CycleLysogenic CyclePhage DNA or
genome injected into host cell
Viral DNA joins host DNA forming a provirus
When an activation signal occurs, the phage DNA starts replicating
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Lysogenic CycleLysogenic CycleViral DNA (part of
provirus) may stay inactive in host cell for long periods of time
Provirus Replicates during each binary fission in bacteria and Mitosis in Eukaryotic Cells
Over time, many cells result which contain the provirus
Lytic and Lysogenic Cycle
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Viral LatencyViral LatencyOnce a provirus cell is activated, host cell enters
the lytic cycle
•New viruses form and the cell lyses (bursts)
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Latency in Latency in EukaryotesEukaryotesSome eukaryotic
viruses remain dormant for many years in the nervous system tissues
Chickenpox (caused by the virus Varicella zoster) is a childhood infection
It can reappear later in life as shingles, a painful itching rash limited to small areas of the body
SHINGLES
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Latency in EukaryotesLatency in EukaryotesHerpes viruses also
become latent in the nervous system
A herpes infection lasts for a person’s lifetime
Genital herpes (Herpes Simplex 2)
Cold sores or fever blisters (Herpes Simplex1)
SKIN TO SKIN CONTACT
PASSED AT BIRTH TO BABY
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Interferon are naturally occurring proteins made by cells to fight viruses
Strange and Unusual VirusEpidermodysplasia Verruciformis.
Dr Gaspari, of the University of Maryland, concluded Dede’s affliction was caused by the Human Papilloma Virus (HPV), a fairly common infection usually causing only small warts.Caused by an extremely rare immune system deficiency Leaves body unable to fight the warts. The virus was therefore able to “hijack the cellular machinery of his skin cells” causing them to produce tree-like growths known as “cutaneous horns”.
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“Tree Man” of Java
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The End
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