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Virus – structure & function Viruses are microscopic particles which Do not grow / mature Are parasitic, onlyreproducing within a living organism
Where do Viruses Come From? They’ve been around for at least4000 yeas. Small Pox First virus in recordedhistory Pharoah Ramses V (1196B.C.) had the pot marks associatedwith small pox.
(1) Evolved from Cells Some cells evolved into viruses: By losing their genetic materials, thus requiring thegenetic material of host cells When fragments of a cell’s DNA combined to makesomething new (a virus)(2) Evolved with Cells Simple molecules on earth evolved into: Cells which have self-replicating abilitiesor Viruses which have parasitic abilities, using cells to reproduce.Three Theories on Viruses
Three Theories on Viruses Idea that viruses came to Earth via a meteor Why sucha strange idea? Viruses are so different from everything else onEarth.(3) Alien Theory
• Viruses are simple structures consisting of1. Capsid• A protein coat made of individual protein subunitscalled capsomeres.• Provides the virus with its shape• Makes up 95% of a virus’s sizeVirus – structure & function2. Genetic Material• Genetic material is located inside the capsid.• Can be DNA or RNA
1. Spikes• Located on capsid• Helps viruses attach to cells• Not present on all viruses2. Envelope• Above capsid• A protective coat on somevirusesVirus – structure & function
Viruses & Human Health Many serious diseases are causedby viruses Symptoms are caused bydestruction of the cell the virusesinfect Antibiotics are not effective againstviruses Viral diseases can be prevented with vaccines The body reacts to the vaccine as though it were the realdisease and produces antibodies
How are viruses transmitted? Breathing in air-bornedroplets contaminatedwith a virus. Eating food or drinkingwater contaminated witha virus. Having sexual contactwith a person who isinfected with a sexuallytransmitted virus. Indirect transmission from person to person by a virushost, such as a mosquito, tick, or field mouse. Touching surfaces or body fluids contaminated with a virus.
Diseases caused by viruses Smallpox This variola virus had many forms andcontinues to be a required vaccination. Smallpox in its worse forms– hemorrhagic–flat – had the highest fatality rates withonly a 10 percent or less chance of survival. Cancer Viral cancers only occur in a minority ofinfected persons (or animals). Cancer viruses come from a range of virusfamilies, including both RNA and DNAviruses.
Diseases caused by viruses AIDS has been categorized as an epidemicby the CDC and the life expectancy hasbeen extended despite the lack of avaccination or cure. The Ebola virus is much more deadly in theshort term. Polio or infantile paralysis is a viraldisease that is transmitted through thefecal-oral course HIV / AIDS Human immunodeficiency virus (HIV) leads to acquired immunedeficiency syndrome (AIDS), which cripples a human’s immunesystem.
Vaccines This is a prepared virus that has been HEATED tokill/destroy the genetic material while leaving the capsid(protein coat) intact. Vaccine is injected into a host, to trigger the immunesystem. Immune system builds antibodies specific to that virus.
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