Name: ___________________
SCIENCE – CLASSIFICATION
CL-8
March 27/8, 2008
Section #/color: __ / ________
SCIENCE – CLASSIFICATION
What is a virus? How do we prevent disease and infection?
Mrs. P’s NOTES and PRACTICE
1. HOW DO PATHOGENS ENTER OUR BODY? (INCLUDE A PICTURE!)
 Through your eyes.
 Through your respiratory canals.
 Through the genital/excretory openings.
 Through the mouth.
 Through the skin (injections, cuts, bites).
2. HOW DO PATHOGENS END UP HURTING US?
1. The pathogens attach themselves to cell at specific sites on the cell membrane
(receptor sites).
2. If the pathogens are certain forms of bacteria (e.g. strep), they may reproduce
OUTSIDE the cell and make toxins (poisonous chemicals) that kill the cell
FROM THE OUTSIDE.
3. If the pathogens are other forms of bacteria OR a virus, they will enter the
cell and reproduce. Their presence makes the cell weak and eventually kills it.
The newly “born” microbes will then leave the cell and move on to attack other
healthy cells.
3. HOW DO OUR BODIES FIGHT PATHOGENS?
NATURAL DEFENSES:
1. 1st line of defense – skin and mucous membranes in nose and throat – act as a
filter/barrier to pathogens.
2. Macrophages (a type of white blood cell) will recognize foreign bacteria and
kill it.
3. After the extended presence of pathogens in the body, the immune system will
make other types of white blood cells to help attack the pathogen:
 Antigens – molecules on the surface of a pathogen that the body
recognizes as foreign; OR molecules that get produced on the surface of
infected cells as a way for the body to recognize they are infected.
 B cells – (white blood cells) produce tagging devices (antibodies) that are
trained to recognize specific antigens on infected cells; they attach
themselves to the antigen so that the body recognizes that the cell they
are attached to needs to be destroyed.
 T cells – (white blood cells) attack and destroy infected cells that have
antigens on their surface.
DRUGS:
1. Antibiotics (e.g. Penicillin – a type of FUNGI!) – drugs used to TREAT a
bacterial infection; they work by killing bacteria, stopping bacteria from
functioning correctly (inhibit cell wall or DNA production), or weakening
bacteria enough so that the immune system is able to kill the bacteria fully.
2. Vaccines – live/dead microbes, parts of microbes, etc. that are added to the
body so that it can build up the proper antibodies to PREVENT any possible
full-fledged infection (bacterial or viral) in the future.
4. WHAT ARE THE MAJOR TYPES OF PATHOGENS and HOW DO PATHOGENS “FIGHT BACK?”
 Pathogens can be bacteria, fungi, parasites, or viruses.
 Pathogens can alter the form of the antigen on their surface so the immune
system has a hard time recognizing them and fighting them.
 Genetic mutations (i.e. changes) in the DNA of the pathogens allow them to
become resistant to (even attack!) antibiotics and other drugs.
PRACTICE.
Place the letters from the statements in COLUMN B in the blanks next to the corresponding terms or ideas in
COLUMN A. Use the attached notes and your memory of your experience in class today to help you do this.
COLUMN A
___ 1. Vaccine.
___ 2. Skin, Respiratory, Genital/Excretory,
and Eyes.
COLUMN B
A. Pathogen attaches to cell, reproduce outside or
inside, weakens and kills cell, and moves on to
other cells.
B. Special molecules produced by white blood cells
that help the body to recognize and destroy
pathogens.
___ 3. T-Cell, B-Cell, Macrophages.
C. What microbes will do to fight and/or reverse
the effects of our immune system and drugs.
___ 4. Virus, Fungi, Bacteria, Parasite.
___ 5. Antibody.
___ 6. Alter their genetic material and/or
antigens.
D. A drug used to PREVENT bacterial OR viral
infections.
E. Different types of white blood cells.
F. The four pathogens that cause disease and
infection.
___ 7. Skin and mucous membranes.
G. A type of medicine used to FIGHT bacterial
infections ONLY.
___ 8. How our cells become “sick” and die
due to pathogens.
H. Our body’s first line of defense against disease
and infection.
___ 9. Antibiotics.
I. The avenues through which pathogens can get
into our bodies.