1. Viruses & other Pathogens

2. The 8 characteristics of Living things
Everything is made of cells
Reproduction
Metabolism
Homeostasis
Heredity
Responsiveness
Growth & Development
Change over time/adapt

3. A virus is a tiny, nonliving particle that enters and then reproduces inside a living cell.
No organisms are safe from viruses.

4. Most biologists today consider viruses to be nonliving because viruses do not have all the characteristics essential for life.
Viruses are not cells and do not use their own energy to grow or to respond to their surroundings.
Viruses also cannot make food, take in food, or produce wastes.

5. Almost all viruses destroy the cells in which they multiply.

7. All viruses have two basic parts: a protein coat that protects the virus and an inner core made of genetic material.

8. The Structure of a Virus
Protein Capsule
Surrounds genetic material
DNA
RNA
No means of independent metabolism or growth
No means of independent reproduction
Dependent on host life form
Can evolve or change over time

9. The three ways of Entry into Host Cell
Plants – through tear in cell wall of cell
Bacteria – punches hole and injects DNA or RNA
bacteriophage
Animals – Endocytosis – cell engulfs bacteria

10. Virus as Pathogen – disease causing agent
Mumps
Measles
Chicken Pox
AIDS Rabies Cold Hanta
Hepatitis Flu Polio SARS
Hemorrhagic Fever Yellow Fever
Small Pox

11. Mode of Transmission Insects – ticks, mosquitoes
Exchange of body fluids – sex, kissing, even oral sex, sometimes sweat
Airborne – coughing, sneezing puts viral particles out in aerosols
Direct contact – touching; many viruses such as flu and cold are long lived on surfaces

12. Host Cell Specificity
Many can only infect certain tissues or types of cells (must have proper receptors)
Hepatitis – liver cells
Many cancers – human papilloma virus –
Influenza, Hanta virus – lung tissue
Tobacco Mosaic Virus – only plant cells

13. Combating Viral Pathogens
Vaccines – A substitute host such as fertilized chicken egg is infected
Eggs produce antibodies to combat virus
Virus is heat killed & antibodies are injected in a vaccination
Jenner – cowpox injected to combat small pox
Class of drugs called interferons work by hindering the uptake of viral particles in cells – commercial - Tamaflu

14. Uses for Viruses Non – pathogenic viruses Pathogenic viruses
Used in genetic engineering to transfer genetic material
Pathogenic viruses
Biological Warfare
Smallpox
Ebola and other hemorrhagic fevers

15. Prions – mad cow disease - bse
Bovine spongiform encephalopathy
Incorrectly folded proteins
Cause normal proteins to fold in such a way as to be not functional

16. Do viruses have the characteristics of living things?
Cellular organization NO
Reproduction with help from host cells
Metabolism NO
Homeostasis NO
Heredity with help from host cells
Responsiveness limited
Growth & Development NO