Download U8-Topic3_Protecting against disease

Grade 11A
Name:______________________________ Class: _________________
Active reading 11A – Microbiology and Biotechnology
Topic 3: Protecting against disease
What is the body’s first line of defense?
A pathogen is a microorganism, virus, or protein that can cause a disease. The
body’s first defense against pathogens is two typical barriers that prevent
pathogens from entering the body: the skin and mucous membranes.
The skin is the first barriers. Oil makes the skin surface acidic and inhibits the
growth of many pathogens. Sweat contains enzymes that kill bacteria. Mucous
membranes are a second barrier. They cover internal body surfaces, such as the
digestive, respiratory, and reproductive tracts. Mucous membranes produce a
thick, sticky fluid, called mucus. Mucus traps pathogens before they can cause
infection.
What is the body’s second line of defense?
Pathogens can sometimes cross the body’s physical barriers. When this occurs,
the body responds with a second line of defense, called nonspecific immune
responses. These responses, described in the table below, are general. That is,
they occur in response to any type of invading pathogen. Therefore, the
responses depend on the body’s ability to distinguish its own cells from invaders.
Response
Fever
Protein activation
Inflammation
Description
Body temperature often rises to fight a pathogen. High body
temperature, or fever, is harmful to many bacterial pathogens.
The body also produces proteins that attack pathogens.
Complement proteins create holes in bacterial cell membranes.
Proteins called interferones prevent viruses from functioning.
An injury or infection in the body causes inflammation. During
inflammation, chemicals and cells gather at the site of infection to
destroy pathogens. See the diagram below
Grade 11A
Name:______________________________ Class: _________________
What is the body’s third line of defense?
Pathogens have unique proteins, called antigens, on their surfaces. Antigens help
the body identify pathogens as invaders. A macrophage is a white blood cell that
ingests and destroys general pathogens. After a macrophage destroys a pathogen,
it displays the pathogen’s antigens on its surface.
This display alerts the immune system to an invader and activates the specific
immune response. This response occurs when general responses fail and when a
pathogen infects a cell. It involves white blood cells, or immune cells, that target
particular pathogens.
Immune cells have receptors that only recognize certain antigens. The shape of
these receptors exactly matches the shape of specific antigens. As shown below,
these receptors bind to antigens. Such binding produces many more specific
white blood cells to fight the infection.
Grade 11A
Name:______________________________ Class: _________________
Key words
Pathogen
Nonspecific immune response
Inflammation
Macrophage
Specific immune response
Mucus
A. Write one or more sentences to answer the following questions
1. What two physical barriers make up the first line of defense?
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2. What is one way mucous membranes prevent infections?
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3. What three defenses occur when a person breaths in a virus that crosses
the mucous membranes in the respiratory tract?
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4. Does fever only result from a bacterial infection? Explain your answer.
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5. What does a macrophage do after it ingests a pathogen?
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Grade 11A
Name:______________________________ Class: _________________
B. How are the nonspecific immune responses different from the specific
immune responses?
nonspecific immune responses
Difference
C. Complete the graphic organizer:
The body’s
second line
of defense
responses
specific immune responses
Grade 11A
Name:______________________________ Class: _________________
D. Circle the letter of the phrase that best answers the question.
1. What does our body target as pathogens?
a.
b.
c.
d.
all bacteria
cancerous cells
disease-causing bacteria
microorganisms responsible for decay of dead material
2. What causes the production of interferons?
a.
b.
c.
d.
bacteria
chemicals
viruses
vaccines
3. An antigen is __________.
a. a specific example of an antibody produced to eliminate a harmful
microbe
b. a white blood cell in your body that engulfs and eliminates foreign
particles
c. an organism or substance that creates a response by your
immune system
d. a type of chemical given as medicine to patients with allergies