Living or Not?

Living organisms must…Be made of :carbon, hydrogen, oxygen,

nitrogencells

Be able to: reproducegrow and develop, repair selfeat or produce foodexchange material with

environmentmoverespond 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) = 10-9 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 acidsΧ 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

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]