VIRUSES21 SEP 1224 SEP 12

How did scientists come up with the term VIRUS?

In the 1890s, two scientists independently investigate the cause of the disease.

How did scientists come up with the term VIRUS?

The scientists extracted sap from unhealthy leaves and put it on the leaves of normal, healthy plants

How did scientists come up with the term VIRUS?

They filtered the sap to remove bacteria and then repeated the tests.

How did scientists come up with the term VIRUS?

Their conclusion was that something smaller than bacteria were causing the disease.

VIRUS

Latin – Slime; poisonous liquid

Modern – Agent that causes

infectious disease

If viruses are smaller than bacteria, how big do you think they are?

PREFIX SYMBOL FACTORyotta Y 1024

zetta Z 1021

exa E 1018

peta P 1015

tera T 1012

giga G 109

mega M 106

kilo k 103

hecto h 102

deka da 101

deci d 10-1

centi c 10-2

milli m 10-3

micro µ 10-6

nano n 10-9

pico p 10-12

femto f 10-15

atto a 10-18

zepto z 10-21

yocto y 10-24

What are the main components of a virus?

Viruses are simple agents

Capsid – Protein Shell

Nucleic Acid Core

Envelope –Outer Membrane

Surface Receptors

CapsidsPROTEINS

IsoleucineIle, I

Asparagine, Asn, N

Serine, Ser, S

Proline, Pro, P

Glutamic acid, Glu, E

Threonine, Thr, T

Amino Acids

Helical Viruses

Tobacco Mosaic Virus

Polyhedral Viruses

Adenovirus

Complex Viruses

Bacteriophages

T4

CapsidHead

Tail sheath

DNA

T4 Bacteriophage Tobacco Mosaic Virus

Influenza Virus

RNA

Tail fiber

RNA

Capsid proteins

Surface proteins

Nucleic Acid CoreDNA Deoxyribonucleic acid

AdenineGuanineThymineCytosine

Nucleic Acid CoreRNA Ribonucleic acid

AdenineGuanineUracilCytosine

Nucleic Acid Core

Viruses genomes can be either double stranded or single

stranded.

Nucleic Acid Core

Viruses can only have one type of

nucleic acid. It must be DNA or RNA,

not both!

Envelope

Helps get the virus into the host cell.

Envelope

Acquired from the host cell.

Envelope

Is sensitive and can be disrupted by desiccation, heat, and exposure to

detergents.

Receptors

Help the virus recognize the

host cell.

Receptors

Are very specific – have a key and lock relationship.

Envelope

Protein ShellCapsid

Nucleic Acid

Receptors

DNA or RNA

Membrane around virus

Proteins that help virus get into proper host