Download Defense against infectious disease

Instructions: Read Pages: 162-168 n your IB Biology Textbook. Then define the below vocabulary
words & address the below learning objectives.
TOPIC 6.3 STUDY GUIDE SL Defense against infectious disease
Define the following vocabulary words:
Pathogen
Disease
Virus
Metabolic pathway
Antibiotics
Phagocytes
Leucocytes
Antigens
Antibodies
Immune system
HIV
lymphocytes
Address the following Learning Objectives:
6.3.1
6.3.2
6.3.3
6.3.4
6.3.5
6.3.6
6.3.7
6.3.8
Define pathogen. Pathogen: an organism or virus that causes a disease.
Explain why antibiotics are effective against bacteria but not against viruses. Antibiotics block
specific metabolic pathways found in bacteria. Viruses reproduce using the host cell’s metabolic
pathways, which are not affected by antibiotics.
Outline the role of skin and mucous membranes in defence against pathogens.
Outline how phagocytic leucocytes ingest pathogens in the blood and in body tissues. Details of the
subdivisions and classifications of phagocytes are not required.
Distinguish between antigens and antibodies.
Explain antibody production. Many different types of lymphocyte exist. Each type recognizes one
specific antigen and responds by dividing to form a clone. This clone then secretes a specific
antibody against the antigen. No other details are required.
Outline the effects of HIV on the immune system. The effects of HIV should be limited to a reduction
in the number of active lymphocytes and a loss of the ability to produce antibodies.
Discuss the cause, transmission and social implications of AIDS.
Helpful Websites:
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B Cell Animation
o http://www.bio.davidson.edu/courses/immunology/Flash/Bcellmat.html
HIV Infection
o http://www.aegis.com/topics/virus/
o http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter22/animation__hiv_replication.html
o http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter22/animation__how_the_hiv_infection_cycle
_works.html
Immune System Overview:
o http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter22/animation__the_immune_response.html
Antigens & Antibodies:
o http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter22/animation__antigenic_determinants__epi
topes_.html
Practice Questions:
1. Define pathogen.
“An organism or virus that causes disease.” (1 p. 49)
2. List some examples of illness which are pathogenic and non-pathogenic.
Pathogenic:
Non-pathogenic:
3. Outline one example of an infection by each of the following types of pathogens:
Type of pathogen
BACTERIA
Example disease
Cholera
Pathogen
Vibrio cholerae
Method of
transmission
Contaminated
drinking water
or food
Symptoms
Severe diarrhea
and vomiting
Treatment
Urgent oral
rehydration,
antibiotics
Dangers
Death by
dehydration
VIRUS
FUNGI
PROTOZOA
4. Explain why antibiotics can be used to treat bacterial infections but not viruses.
Link thought: how does overuse of antibiotics lead to antibiotic resistance?
5. In the space below, draw and annotate two simple line graphs to distinguish between the action of
bacteriostatic and bacteriocidal antibiotics:
Link thought: how does overuse of antibiotics lead to antibiotic resistance?
6. Outline the role of skin and mucous membranes in primary defense (acting as barriers against pathogens):
Skin is a tough barrier
Hairs, e.g. nose
Mucous, such as in
nose, airways
Acidic conditions (e.g.
stomach and vagina)
Lysozymes
Natural organisms
7. State the functions of the following components of the blood:
Lymphocytes
Immune response – e.g. B-cells and T-cells
Phagocytic leukocytes
(macrophages)
Erythrocytes
Platelets
Plasma
8. Outline how phagocytic leukocytes ingest pathogens in the blood and body tissues.
Method of membrane
transport:
How does it work?
9. Distinguish between antibodies and antigens.
A globular protein. (revise levels of protein structure)
Antibody
Produced as part of the immune response.
Specific to the antigen on the pathogen – the antigen binding
site is analogous to the active site of an enzyme.
Link thought: how is this important in ABO blood typing and how is that an example of codominance?
10. Explain how antibodies are produced.
There are many different types of lymphocytes in
the immune system.
Link thought: antibodies are globular proteins produced by lymphocytes. Explain how the final antibody is
produced from the genetic information in the lymphocyte nucleus, to a level of detail appropriate to your level
of study.
11. State the role of memory cells following an infection.
12. Define the terms HIV and AIDS
HIV =
AIDS =
13. Outline the effects of HIV on the immune system.
Effect on lymphocytes
Effect on antibody production
Effect on health
14. Discuss the cause, transmission and social implications of HIV/AIDS.
Cause
Methods of transmission
Social implications
15. Outline some of the economic impacts of HIV in the developing world.
16. The graph below shows the progression of a typical case of HIV. CD4 cells are those attacked by the HIV virus.
Once levels of these lymphocytes drop below a critical value, the immune system is no longer able to fight
infection and AIDS is diagnosed.
a. State the CD4 cell count at which AIDS is likely to be diagnosed.
b. Deduce, with a reason, the period in which a person infected with HIV is most likely to pass it on to
someone else.
c. Describe the effects of HIV on the immune system over time.
d. Identify the period in which other illnesses are most likely to result in death.
Works Cited
1. Allott, Andrew. IB Study Guide: Biology for the IB Diploma. s.l. : Oxford University Press, 2007. 978-0-19-915143-1.
2. Mindorff, D and Allott, A. Biology Course Companion. Oxford : Oxford University Press, 2007. 978-099151240.
3. Clegg, CJ. Biology for the IB Diploma. London : Hodder Murray, 2007. 978-0340926529.
4. Campbell N., Reece J., Taylor M., Simon. E. Biology Concepts and Connections. San Fransisco : Pearson Benjamin
Cummings, 2006. 0-8053-7160-5.
5. Taylor, Stephen. Science Video Resources. [Online] Wordpress, 2010. http://sciencevideos.wordpress.com.
6. Burrell, John. Click4Biology. [Online] 2010. http://click4biology.info/.
7. IBO. Biology Subject Guide. [Online] 2007. http://xmltwo.ibo.org/publications/migrated/productionapp2.ibo.org/publication/7/part/2/chapter/1.html.