VIRUSES
21 SEP 12
24 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
yotta
zetta
exa
peta
tera
giga
mega
kilo
hecto
deka
deci
centi
milli
micro
nano
pico
femto
atto
zepto
yocto
SYMBOL
Y
Z
E
P
T
G
M
k
h
da
d
c
m
µ
n
p
f
a
z
y
FACTOR
1024
1021
1018
1015
1012
109
106
103
102
101
10-1
10-2
10-3
10-6
10-9
10-12
10-15
10-18
10-21
10-24
What are the main components of a
virus?
Capsid –
Protein Shell
Viruses are
simple
agents
Nucleic Acid
Core
Envelope –
Outer Membrane
Surface
Receptors
Capsids
PROTEINS
Proline, Threonine,
Pro, P
Thr, T
Glutamic
acid,
Glu, E
Isoleucine Asparagine,
Asn, N
Ile, I
Amino Acids
Serine,
Ser, S
Helical Viruses
Tobacco Mosaic
Virus
Polyhedral Viruses
Adenovirus
Complex Viruses
T4
Bacteriophages
T4 Bacteriophage
Head
Tail
sheath
DNA
Tobacco Mosaic
Virus
RNA
Influenza Virus
RNA
Capsid
Tail
fiber
Capsid
proteins
Surface
proteins
Nucleic Acid Core
DNA
Deoxyribonucleic acid
Adenine
Guanine
Thymine
Cytosine
Nucleic Acid Core
RNA
Ribonucleic acid
Adenine
Guanine
Uracil
Cytosine
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.
Capsid
Protein Shell
Nucleic Acid
DNA or RNA
Envelope
Membrane around virus
Receptors
Proteins that help virus
get into proper host