Download Virus PPT Pre-AP 14-15

1/24
• Grab: Orange Virus Booklet 
• Reminder: if you missed test, make-ups will be
– after school 2:45 – 3:30 p.m.
– tomorrow morning 6:45 a.m.
– Enrichment today (but finish after school)
• https://www.youtube.com/watch?v=ugM1nIhfIA&index=13&list=PL0CB02BD6E00
EEB09
Viruses are not classified in any
kingdom. They show no traits
like the living things in the 6
kingdoms we will be studying.
WHAT IS A VIRUS?
A. General Characteristics
1. A virus is an infectious agent made up of – nucleic
acid (DNA or RNA), wrapped in protein coat
a. they have no nucleus, no organelles, no
cytoplasm or cell membrane – non-cellular particle
b. viruses have either – DNA or RNA, but not both
vs
c. viruses with RNA that transcribes into DNA (using enzyme
reverse transcriptase) are called – retroviruses
Ex: HIV, flu (influenza), cold
RNA viruses have a high rate of mutations – replication of
RNA does not involve proofreading step (as in DNA
replication)
HIV Infected Cell
(This is the reason why HIV is so incurable.)
2. Viruses are - parasitic - organism that depends
entirely upon another living organism (host) for its
existence in such way that it harms that
organism.
A flea is a parasite to a dog
and is harmful to the dog.
B. Examples
1. Bacteriophage—viruses that infect a bacteria
Capsid (protein coat)
2. Flu (influenza), HIV
DNA
Tail
fibers
Envelope—has marker
proteins + carbs
derived from host cell
RNA
Capsid
Capsid
Nucleic Acid
Bacteriophage—a virus that infects
bacteria (bacteria is the host)
C. Replication (reproduction): How a virus spreads.
***A virus CANNOT reproduce by itself—it must invade a host
cell and take over its activities.
1. Virus (bacteriophage) invading a bacterium (E. coli)
Virus attaches
DNA of virus
to cell
enters cell
Virus uses what it
needs from cell +
makes more virus
Virus DNA becomes part of
cell’s DNA
Lytic = split
Cell bursts, new
viruses are
released
Cell divides, replicating
DNA of virus
2. During Lysogenic Cycle, it is possible for viral DNA to separate
from host cell DNA and cause cell to enter Lytic Cycle and
replicate new viruses
Virus attaches
DNA of virus
to cell
enters cell
Virus uses what it
needs from cell +
makes more virus
Virus DNA becomes part of
cell’s DNA
Lytic = split
Cell bursts, new
viruses are
released
Cell divides, replicating
DNA of virus
3. Virus invading an animal cell:
Ex: HIV invading human cell
Virus DNA becomes part of cell’s DNA
Virus particle
enters human cell
by endocytosis
RNA
replicates
Envelope of HIV
contains marker
proteins + carbs
derived from host
cell
New virus
buds off
4. Capsid proteins of a virus bind to receptors on cell
surface and “trick” cell into allowing it inside.
5. Because of this fit between virus and cell receptors,
most viruses are specific for cells they infect.
Ex: the rabies virus only infects brain or nervous
cells
Virus
Cell
Receptor
Sites
D. Importance:
1. Harmful
a. Causes disease—pathogenic
Disease producing agent—pathogen
b. Human Diseases:
DNA: chicken pox, mono, cold sores,
genital herpes, warts, hepatitis,
smallpox
RNA: cold, influenza, polio, AIDS,
rabies, Ebola
c. Viruses disrupt the body’s normal
equilibrium/balance (homeostasis)
d. Viruses can be prevented with
vaccines, but NOT treated with
antibiotics.
2. Beneficial
a. genetic engineering – harmless virus carries
good genes into cell
Structure
Reproduction
Genetic material (DNA or
RNA) + capsid
Copies itself only inside
host cell
Cell membrane, cytoplasm,
genetic material, organelles
Cell division --Asexual or Sexual
DNA and RNA
Genetic Material
DNA or RNA
Growth and
Development
NO
YES
NO
YES
NO
YES
YES
YES
Obtain and
Use Energy
Response to
Environment
Change over time
How many characteristics
of life do viruses possess?
*contains Genetic Material
*change over time
Are viruses living?
1/29
• Pick up:
– HIV evolving Menace + w.s.
• Get out Dr. Virus
– DO NOT TURN IN, WE WILL GRADE IN CLASS!
• REMINDER – QUIZ MOVED TO THURSDAY!
1/30
•
•
•
•
Reminder QUIZ this Friday over virus notes
I have your TEST GRADES so STOP ASKING!
WARM-UP, Paper needed
Get out Virus notes
Warm-Up
• Get out a spare sheet of paper. YOU MAY NOT
USE NOTES!!!!!
1. What is a Bacteriophage?
2. Why are Retroviruses so hard to kill? What is
an example of a Retrovirus?
3. Describe the Lytic and Lysogenic Cycles.
4. How do viruses invade Animal Cells?
Warm-up
1. Describe the structures of the HIV virus
to the right 
2. Are all viruses bad? If not, explain a positive use for Viruses
3. After you are given a cell and surface marker find your match
and go visit Ms. Lust for some “medicine”.