VIRUSES
GIVE
THE WORKSHEET A TRY!!
ANSWERS CAN BE FOUND IN
CHAPTER 19 SECTION 2 on VIRUSES
(you need to look at the WHOLE
SECTION).
HELPFUL START PAGE= 474
Bacteria & Viruses
WHAT’S THE DIFFERENCE??
A little review…
A little review…
Prokaryotes are DIVERSE
• shape,
• the chemical nature
of their cell walls,
• the way they move,
• and the way they
obtain energy.
A little review…
ARCHEABACTERIA

Live in EXTREME
conditions.

Do NOT have
PEPTIDOGLYCAN in their
cell walls


Their DNA is so similar to
Eukaryotes – possible
ancestors
Example: Methanogens
EUBACTERIA

NEWER bacteria

It’s all around YOU
 In
our intestines
 Water
systems
 Land

Has PEPTIDOGLYCAN
in its cell wall
E. coli
Eubacteria come in all shapes…
Bacilli (Rods)
E. coli
Cocci (Spherical)
Streptococcus
Spirilla (spiral)
Spirillum volutan
Eubacteria also differ in their…
Cell Walls
 Have really thick
peptidoglycan
covered
OR
 Thinner walls
surrounded by a
lipid layer
Movement

Non movers

Move slowly in their
own secretion

Have flagella that
propel them along
quickly!
Eubacteria also differ in the way
they eat…
 Chemoheterotrophs-
 Photoheterotrophs-
consumers
consumers
photosynthetic &
 Chemoautotrophs-
use carbon
compounds to make food w/out sunlight.
 Photoautotrophs-
do photosynthesis like
green plants; no chloroplasts but have
chlorophyll a
Eubacteria have different forms of
release of energy
 Obligate
aerobes- have to have
oxygen; do cell respiration
 Obligate anaerobes- do
fermentation; “allergic” to oxygen
 Faculatative anaerobes- can do
either one.
Can
live just about anywhere.
IMPORTANCE OF BACTERIA
 Producers
that capture energy by
photosynthesis.
 Decomposers—breaking down nutrients
 Ex.
Nitrogen fixation
 Human
uses-
 Remove
poisons, break down petroleum, used
to make yogurt, mine minerals, syntesize
drugs
 E.coli in our lower intestines, make vitamins we
can’t get, further break down our food
Viruses: “Poison” – RNA or DNA
surrounded by protein coat
INFECTS
BACTERIA
How viruses infect
 Lytic
Infection-
 Virus
“tricks” its way into cell- CAPSID
 Cell
replicates viral DNA
 Cell
assembles new viral proteins
 Cell
bursts or lyses from too many viruses.
 Lysogenic
infection-
 Viral
DNA is inserted into the DNA of the host cell,
then just sits there until something triggers the lytic
cycle.
When
with it.
host cell replicates, the viral DNA is replicate
Retroviruses
Nucleic
acid is RNA instead of DNA
Some retroviruses cause cancer in
animals (including humans).
HIV is a retrovirus (causes AIDS).
HIV

Human Immunodeficiency Virus

Why is it so dangerous?
 No
cure, only treatment
 Attacks/Disables
 Host

key cells in immune system (helper T cells)
no longer able to fight off infection
May remain latent for long periods.
 Infected
person may appear healthy but is contagious.
 Lysogenic
Phase (latent stage)- Viral DNA inserted into host
cell’s DNA and copied prior to cell division.
 Lytic
Phase (active stage) – Viral Proteins rapidly reproducing
and infecting many cells
Viruses vs Cells
VIRUSES
 Are
not made up of
cells
 Can’t
live without host
 Don’t
respond to
environment
 Don’t
obtain or use
energy
CELLS
 Reproduce
 Grow
 Can
live without host cells
 Respond
to their environments
 Obtain
energy (autotrophs or
heterotrophs
 Release
energy (aerobic or
anaerobically).
Viruses and cells both
Reproduce
Have
a genetic code (DNA or RNA)
Evolve
Common Viral Diseases
 Rhinoviruses
cause the common cold
 HPV
(Human papillomavirus) can cause cervical
cancer in women
 Herpes
simplex viruses cause mouth and/or genital
sores, lesions, and ulcers.
 Influenza
 HIV
viruses cause the flu
(Human Immunodeficiency Virus) causes AIDS and
weakens the immune system
Rabies
Chicken pox
Hand, foot and mouth disease
shingles
Controlling Viruses
PREVENT
– with vaccines
http://www.pbs.org/wgbh/nova/teachers/body/genetic-engineer-avian-flu.html
TREAT – with rest and hydration for most viral
infections
Antiviral drugs available for some viral
infections (limited success)
Antibiotics DO NOT work on viruses.
Controlling Viruses
 Vaccines
stimulate the immune system to create
antibodies that recognize a certain virus.
 Vaccines
 These
will NOT cure you if you are already sick.
antibodies patrol your body and if they
recognize that virus…they call in reinforcements
and your immune system goes to battle!
How do we fight Illness?
 Immune
system- cells that inactivate or
destroy pathogens
Nonspecific
Skin,
mucus, sweat, tears
Inflammatory
response
Fever
Specific
Hummoral
Acquired
Immunity
Immunity
Nonspecific Immunity
 Skin
 Mucus,
 Break
saliva, tears contain lysozymes
down cell walls of bacteria
 Inflammatory
 White
Response –happens if tissue damage
blood cells: granulocytes that engulf (EAT) pathogens
 Infected
tissue becomes painful and swollen
 Fever
 Chemicals
released by immune system raise body temperature,
so that pathogens can’t survive.
 Heart
rate increases, producing more white blood cells
Specific Immunity
 Antigens
trigger the response
 Viruses,
 “Self”
bacteria, and other pathogens that trigger immune response
and “Non-self”
 Lymphocytes
 Tag,
(T Cells and B Cells)
destroy and remember foreign bodies including pathogens
Acquired Immunity
 The
production of immunity against diseases
Vaccination
Injection
of a weakened form of a pathogen to
stimulate immune system
Antibiotics
Compounds
that kill bacteria without harming
host cells (prevent bacterial reproduction)
No
effect on viruses