chapter 19 notes viruses characteristics of viruses prokaryotic or eukaryotic: neither (no...
TRANSCRIPT
CHAPTER 19 NOTES
VIRUSES
CHARACTERISTICS OF VIRUSES
Prokaryotic or Eukaryotic: Neither (no organelles or membranes)
Unicellular or Multicellular: Neither (nucleic acid covered by a protein)
Autotroph or Heterotroph: Neither (food is not metabolized for energy)
Which Kingdom do they belong to? None
CHARACTERISTICS OF VIRUSES
2 MAIN PARTS OF A VIRUS:
1. PROTEIN COAT (CAPSID): PROTECTS THE NUCLEIC ACID CORE
2. CORE OF NUCLEIC ACID (CAN BE DNA OR RNA)
An envelope is found in some viruses (usually those that infect animal cells). It is an additional protective coating.
Many viruses have projections on their surface that allow it to enter a host cell.
EXAMPLE OF A BACTERIOPHAGE
VIRAL DNA
SHEATH
TAIL FIBERS
PROTEIN COAT (CAPSID)
HOW DO VIRUSES MULTIPLY?
Viruses perform replication in other cells called hosts.
The two replication cycles that viruses go through are the lytic and the lysogenic cycles.
The two cycles differ because in the lytic cycle a virus immediately replicates after entering the cell and in the lysogenic cycle the viral DNA replicates itself in a way that doesn’t kill the host cell immediately.
See next page for drawings of the cycles.
LYTIC CYCLE
LYSOGENIC CYCLE
HOW ARE VIRUSES CLASSIFIED?
VIRUSES CAN BE CLASSIFIED BY:
– A. SHAPE
– B. HOST
– C. FUNCTION
Examples of Different Types of Human Viruses
Influenza (Flu)
Examples of Different Types of Human Viruses
HIV
Examples of Different Types of Human Viruses
Smallpox & Hanta virus
Examples of Different Types of Human Viruses
Marburg & Lassa
Examples of Different Types of Human Viruses
Ebola
THREE TYPES OF HOSTS
A. PLANTEx. Tobacco Mosaic Virus
B. ANIMALEx. Rabies, Foot & Mouth Disease
C. HUMANEx. Common cold, measles, chicken pox,
mumps, HIV
TREATMENT OF VIRAL DISEASES
Viral diseases cannot be cured by antibiotics.
Generally with viral infections you are limited to relieving symptoms while your immune system battles the virus.
HUMAN USES FOR VIRUSES
1. VACCINES When you inject a person with a harmless –
weakened or dead form of a virus This stimulates the immune system to produce
cells and proteins that will destroy that type of virus, if it enters the body again
This helped to end epidemics of smallpox, polio and measles
HUMAN USES FOR VIRUSES
2. GENETIC ENGINEERING Viruses can help correct genetic defects by
carrying desirable genes from one cell to another
3. AGRICULTURE Help control pests that destroy human food
crops They eliminate harmful insects without creating
pollution
Virus Video Clips
http://ed.ted.com/lessons/how-pandemics-spread
http://www.youtube.com/watch?v=Rpj0emEGShQ
http://www.youtube.com/watch?v=gf2bObJGFkg