Living or Not?

 Living organisms must… Be made of :carbon, hydrogen, oxygen, nitrogen cells Be able to:reproduce grow and develop, repair self eat or produce food exchange material with environment move respond to stimuli

 Maintain homeostasis  Reproduction  Cellular organization  Metabolism (use energy)  Contain genetic information

Virus (latin for poison) Technically not considered to be living since they do not display most of the characteristics of living things Outside a living cell, a virus is a lifeless chemical carrying out no life function on its own Once inside it is able to “hijack” the cell to reproduce

 Viruses are extremely small  measured in nanometers (nm) = of a metre  Cannot be seen without electron microscopes  They are made of biological particles but are not arranged in cell structures. Biological Molecules: Protein nucleic acids Χ carbohydrates Required to form Χ lipids cell membrane

protective protein coat + nucleic acid core capsid contain either DNA or RNA = 95% of total virus gives its shape Ex) bacteriophage

 The History of Prions The History of Prions

 No fossil evidence  Speculations: 1) once cellular organisms that lived as parasites that gradually lost their own cellular components 2) once free-living, pre-cellular forms that later became parasites of cellular organisms 3) arose from detached fragments of the genetic material of cellular organisms

 Lifeless chemical  Carries out no life functions on its own  Made of a protein coat and nucleic acid

 Not every virus is considered to be a disease-causing agent  Ex) tobacco mosaic virus do not appear to destroy plant tissue  Viruses are generally selective affecting only specific hosts’ cells

 Disease causing agent  Virus (prion/viroid), bacteria, protist, fungi  Responsible for triggering symptoms  Refers to an observable behavior or state.  Symptoms are the infected individual’s response to a foreign object in the body  Fever/chills  Headache  Rash  nausea

 Infection  Foreign organism present in/on an individual  Disease  The set of symptoms that result from an infection by a pathogen having a characteristic set of signs and symptoms  Extrinsic factors/cause  Disorder  Abnormality of function that has a cluster of symptoms  Intrinsic factors/cause  Condition  Perhaps the least specific, often denoting states of health considered normal or healthy but nevertheless posing implications for the provision of health care  Syndrome  The recognizable set of features, signs, symptoms, phenomena or characteristics that together are characteristic of a specific disorder, disease, or genetic condition  the presence of one feature alerts to the presence of the others.

 Medical?  How to treat?  No cure; only influence the symptoms  Employ for patient benefit  Genetic “engineering”  Societal?  How are human behaviour & interactions affected?  Ethical?  Replace need for embryonic stem cells  Use in warfare

 Vehicles for virus (pathogen) transmission

Vector – disease transmitter/carrier ex. Animal saliva Pathogen – Disease “causer” ex. Virus or bacteria

Electron micrograph of Ebola Zaire virus. This is the first photo ever taken,on 10/13/1976 by Dr. F.A. Murphy, now at UC Davis, then at CDC. Diagnostic specimen in cell culture at 160,000 x magnification. [brettrussell.com]