VIRUSES!! Biology

Is a virus Alive?!? Virus – (def) segments of nucleic acids contained in a protein coat Not cells Smaller than prokaryotes (20 nm – 250 nm) Do not grow, do not have homeostasis, do not metabolize, use living cells to reproduce NOT Alive… but can kill us!

Discovery of Viruses Tobacco mosaic disease (1890’s) Determined cause to be smaller than bacteria (called it a virus – “poison”) 1935 – Wendell Stanley determined TMV is a chemical rather than an organism (RNA + protein) …. No cells

Viral Structure Made of two-three parts Capsid – protein coat Nucleic acid RNA – HIV, Influenza, Rabies DNA – HPV, Chickenpox, Mononucleosis Envelope – membrane outside capsid that helps virus enter cells easier

Shapes Helical

Shapes Spherical

Shapes Filaments (Ebola)

Human Immunodeficiency Virus (HIV) First infects macrophages (no cell destruction) Years later infects T cells (cells destruct  AIDS)

Epidemics Spanish Influenza 18 month period 22 million Americans/ Europeans died ~40% of world’s population got sick

Epidemics Smallpox Last known case in 1977 Eradicated in 1980 Samples are still stored in various labs

Epidemics West Nile = 1999 – current Carried by birds, transferred by mosquitoes Flu like symptoms, only deadly to weakened immune systems

Epidemics H1N1 – Current Cannot be transferred by eating pork or chicken

Epidemics Zika – Current May be linked to birth defect (micro- cephaly) Can be transmitted sexually

Hollywood fears? Outbreak Extreme measures are necessary to contain an epidemic of a deadly airborne virus. But how extreme, exactly? View movie segment View movie segment