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Unit 6 notes
Viruses and Immune System
What is a Virus?
- Infectious particle made of only a strand of DNA or RNA surrounded by a
protein coat
- Cannot reproduce on their own
- Size: 50- 200nm
What is a prion?
- Infectious particle made only of a protein that can cause other proteins to
fold incorrectly.
- NO GENETIC MATERIAL
- Size: 2-10nm
What is a viroid?
-
Infectious particles that cause diseases in plants.
Single stranded RNA without a protein coat.
Passed through seeds or pollen
Can stunt the growth of plants
Size: 5-150 nm
18.2 Viral structure and reproduction
MAIN IDEA
Tobacco Mosaic Virus
SUPPORTING DETAILS
- Researched by Dmitri Ivanovsky
- Thought the disease was caused
by bacterium
- Filtered extract of diseased leaves
through pores small enough to
filter out bacteria but still found
extracts of the disease
- Martinus Beijerinck passed the
disease causing agent through an
agar gel and proposed this is what
caused the disease
- Name them viruses, which is
Latin for “poison”
Structure of viruses
- A single viral particle is called a
virion
- The genetic material is
surrounded by a protein shell
called a capsid
- May have a protective outer layer
called a lipid envelop
- This can have glycoproteins
attached to the outer layer
Enveloped Virus
Ex: Influenza
Helical Virus
Ex: Rabies
Polyhedral Virus
Ex: Foot and Mouth
Disease
Lytic and Lysogenic Cycle (Page 516) Know this very well
18.3 Viral Diseases
Main Idea
First Defenses
Supporting Details
- 1st obstacle a virus must get
through is the skin, outer
skeleton, or cell wall of an
organism
- Can penetrate the skin through a
cut or a scrape. Or it can enter
through a mucous membrane
- Most common points of entry are
the mouth, nose, genital area,
eyes, or ears
Types of infections
Example of viral infection
Common Cold
Influenza (Flu)
SARS ( Severe Acute Respiratory
Details
- Over 200 viruses can cause this
- Can mutate as it goes from one
person to another
- Last about a week
- Spreads quickly and can become
a local epidemic
- Infects about 20% of Americans
each year
- 3 subtypes effect humans
- Can jump from one species to
another (Bird flu effecting
humans)
- Very similar to the flu
- 1st appeared in Asia in 2002
- Spread quickly and became a
pandemic
- Has been very rare since 2003
- Retrovirus
- Takes RNA and makes DNA
through reverse transcriptase
- Infects the host as a Lysogenic
infection
- Becomes Lytic as it kills WBC
- Very high mutation rate
Syndrome)
HIV (Human Immunodeficiency Virus
Vaccines
Definition:
A substance that stimulates the body’s
own immune response against invasion
by microbes
How do they work:
Will cause the body to have an immune
response against the weakened virus that
has entered the organism. This will
allow the organism to fight off a true
attack
How are they made:
Made from a pathogen of the same virus
that is weakened
Examples of disease that have vaccines:
- Chicken Pox
- Hepatitis A
- Mumps
- Rabies
- Flue
REMEMBER THAT A VIRUS IS THE ONLY THING THAT A VACCINE WILL
AFFECT. THEY CAN NOT EFFECT BACTERIA.
18.4 Bacteria and Archaea
Plasmid- Small piece of genetic material that can replicate separately from the
prokaryote’s main chromosome
Cell Wall- Barrier for the organism from the outside world. Very rigid
Chromosome- Contains the bacteria’s DNA
Plasma Membrane- Flexible barrier that helps regulate what enters and exits the
organism
Pili- Helps organism to stick surfaces and other organism
Flagellum- Whip-like structure that helps the organism to move
Be able to label these parts of a bacteria and tell the function to illustration is on
page 523
18.6 Bacterial Diseases and Antibiotic
WAYS BACTERIA CAUSE ILLNESS TO A HOST
1. By invading tissues and attacking cells.
- Tuberculosis- invades host WBC and kills them
2. Making poisons/ and toxins
-Ex. Staphylococcus aureus and Clostridium botulinum
Staph can’t be destroyed by high temps and usually isn’t fatal
C. botulinum caused by endospores in canned food and can be fatal
MAIN IDEA
Antibiotics are used to fight bacterial
disease
SUPPORTING DETAILS
- Viruses cannot be treated with
antibiotics
- Bacteria can be treated with
antibiotics
- Antibiotics are chemicals that
slow or stop the growth of
bacteria by destroying the cell
wall
- Can be produced naturally from
bacteria or fungi
- Do not harm animals b/c no cell
wall and that is why viruses are
not effected as well
- Antibiotics if abused can cause
sickness by wiping out colonies
of intestinal microbes
CAUSE OF ANTIBIOTIC RESISTANCE
OVERUSE: Create a selective pressure that benefits the bacteria they are trying to
destroy. Bacteria will become resistant
UNDERUSE: Leads to drug resistance, only kills the weakest bacteria. In doing
this, the strongest bacterial become resistant
MISUSE: Used to help animals grow larger. Bacteria and pathogens can become
resistant to this
Antibiotics are not the primary way to treat bacterial infections. The best way to
treat infections is by preventions. Take care of your body and you will notice you
less sick.