Viruses Viroids and Prions 1

Good Essays
Viruses, Viroids, and Prions copyright cmassengale

1

Are Viruses Living or
Non-living?
Viruses are both and neither
They have some properties of life but not others
For example, viruses can be killed, even crystallized like table salt
However, they can’t maintain a constant internal state (homeostasis). copyright cmassengale

2

What are
Viruses?
A virus is a noncellular particle made up of genetic material and protein that can invade living cells.

copyright cmassengale

3

Viral
History
copyright cmassengale

4

Discovery of Viruses
Beijerinck (1897) coined the Latin name “virus” meaning poison
He studied filtered plant juices
& found they caused healthy plants to become sick copyright cmassengale

5

Tobacco Mosaic Virus
Wendell Stanley
(1935) crystallized sap from sick tobacco plants
He discovered viruses were made of nucleic acid and protein copyright cmassengale

6

Smallpox
Edward Jenner
(1796) developed a smallpox vaccine using milder cowpox viruses Deadly viruses are said to be virulent
Smallpox has been eradicated in the world today copyright cmassengale

7

Viewing Viruses
Viruses are smaller than the smallest cell
Measured in nanometers Viruses couldn’t be seen until the electron microscope was invented in the
20th century copyright cmassengale

8

Size of Viruses

copyright cmassengale

9

Viral
Structure
copyright cmassengale

10

Characteristics
Non living structures
Noncellular
Contain a protein coat called the capsid
Have a nucleic acid core containing DNA or RNA
Capable of reproducing only when inside a HOST cell copyright cmassengale

11

Characteristics
Some viruses are enclosed in an protective envelope
Some viruses may have spikes to help attach to the host cell Most viruses infect only SPECIFIC host cells copyright cmassengale

CAPSID
DNA

ENVELOPE

SPIKE
S
12

Characteristics
Viral capsids
(coats) are made of individual protein subunits
Individual
subunits are called capsomeres copyright cmassengale

CAPSOMERES

13

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