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IB Biology Review Immune System Immune System Vocab Pathogen

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Title: IB Biology Review Immune System Immune System Vocab Pathogen


1
IB Biology Review
  • Immune System

2
Immune System Vocab
  • Pathogen
  • An organism or virus that causes a disease
  • Antigen
  • Any foreign macromolecule (either proteins,
    polysaccharides or structures on the surface of
    bacteria) that triggers an immune response
  • Antibody
  • Antibodies are proteins that bind to particular
    antigens and mark them for elimination from the
    body
  • Antibiotics
  • Any substance that is able to kill or inhibit a
    microorganism such as bacteria

3
Passive versus Active Immunity
  • Passive immunity is due to the acquisition of
    antibodies from another source
  • Such as
  • when a developing fetus acquires antibodies from
    its mother
  • when they are artificially injected into a person
  • Active immunity is when antibodies are produced
    by the person themselves after his or her immune
    system is triggered by antigens

4
Immune System Vocab cont.
  • Virus
  • An infective agent consisting of a protein coat
    surrounding an RNA or DNA core
  • Are not cells and do not possess membranes or
    organelles.
  • They cannot manufacture their own proteins and
    must invade living cells to take over their
    protein production machinery
  • Leucocytes
  • White blood cells
  • Phagocytic leucocytes
  • Specialized white blood cells that engulf
    foreign/invading pathogens and destroy them

5
Different Types of Leucocytes
  • The only ones we need to know are monocytes and
    macrophages, and lymphocytes

6
Why are antibiotics effective against bacteria,
but not viruses?
  • Most antibiotics dont kill bacteria
  • Antibiotics disrupt their reproduction (binary
    fission) by preventing formation of the bacterial
    cell wall in the daughter cells (a part of the
    cells metabolism)
  • Since viruses arent cells and dont produce cell
    walls, antibiotics are not effective against them

7
What are the different components of the immune
system?
  • Skin
  • Mucous membranes
  • Phagocytic leukocytes
  • Antibodies

8
Skin and Mucous Membranes
  • These are a form of external defense preventing
    pathogens from entering the body
  • Skin forms a physical barrier
  • Mucous membranes surround invading pathogens
  • Body senses excess mucous, induces coughing
  • Coughing expels the mucous and the trapped
    pathogen

9
Phagocytic Leucocytes
  • A type of white blood cell
  • Float around the body in blood
  • Phagocyte surrounds the pathogen by endocytosis
  • A vacuole containing the pathogen travels to a
    lysosome
  • The membranes of the vacuole and lysosome fuse
  • Digestive enzymes in the lysosome destroy the
    pathogen
  • The pathogen debris is released by exocytosis

10
Phagocytic Leucocyte Diagram
11
Antibodies
  • Proteins that recognize one kind of antigen
  • Similar to enzymes (lock and key)
  • Lock and key called epitope
  • React by binding to the antigen
  • Destroys antigen
  • Or
  • Inactivates antigen

12
Antibody Production
  • Pathogen is in the body
  • Phagocytic leucocytes called macrophages ingest
    the pathogens
  • Phagocytes present the antigens from the
    pathogens on their cell surface.
  • T-helper cells (another type of leucocyte that is
    specific to that antigen) bind to the antigen
    presented by the macrophages and are
    activated/stimulated
  • Meanwhile, B-cells bind to the antigen, and
    present the antigen as the phagocytes did

13
Antibody Production cont.
  • The activated T-helper cells then bind to B-cells
    and activate them
  • This triggers the B-cells to undergo mitosis to
    form memory cells and plasma cells
  • Short-lived Plasma B-cells secrete antibodies
    quickly that neutralize the pathogen
  • Memory B-cells stay in the blood for a long time
    and enable a more rapid response by the immune
    system if the same pathogen invades in the future

14
HL Only Monoclonal Antibodies
  • Monoclonal antibodies
  • large quantities of a single type of antibody
  • produced in a laboratory
  • Hybridoma cell
  • memory B cell fused with a tumor cell
  • divides uncontrollably, producing a large amount
    of antibodies

15
HL Only Monoclonal Antibody Production
  • 1. Antigens that correspond to a desired antibody
    are injected into an animal
  • 2. B-cells producing the desired antibody are
    harvested
  • 3. Tumor cells are obtained from another source
    (tumor cells grow and divide endlessly)
  • 4. B-cells are fused with tumor cells, producing
    hybridoma cells that divide endlessly, providing
    the desired antibodies
  • 5. The hybridoma cells are cultured and the
    antibodies they produce are extracted and
    purified

16
HL Only Application of Monoclonal Antibodies
Rabies Treatment
  • Rabies usually causes death in humans before the
    immune system can control it.
  • Injecting monoclonal antibodies when a person
    gets infected will control the virus
  • At the same time, the person's body begins making
    its own antibodies
  • Triggers two-fold immune response
  • Passive through injection
  • Active through bodys production

17
HL Only Application of Monoclonal Antibodies
Malaria Diagnosis
  • 1. Monoclonal antibodies are made to bind to
    antigens in malarial parasites
  • 2. A test plate is covered with antibodies
  • 3. The sample is left on the plate long enough
    for malaria antigens (if present) to bind to
    antibodies
  • 4. The sample is rinsed off
  • Any bound antigens are detected using more
    monoclonal antibodies with attached
    color-changing enzyme

18
HL Only Challenge and Response, Clonal
Selection, and Memory Cells
  • B-cells make antibodies
  • The immune system can make 1015 different types
    of antibodies (but not all at once)
  • A few of each type of B-cell are produced and
    they wait until the body is infected with an
    antigen
  • When this occurs, they multiply to form many
    clones
  • This is called clonal selection
  • A clone of B-cells can produces large amounts of
    antibodies quickly and give immunity to a disease
  • Only after the immune system is challenged by a
    disease
  • This is called the challenge and response system

19
Vaccination
  • A weakened or dead version of a pathogen is
    injected into the body, causing the immune system
    to mount a primary response
  • This results in the production of B memory cells
  • The B-cells "remember" the antibodies to produce
    in response to the pathogen
  • When the real pathogen strikes, a secondary
    response occurs, aided by the memory cell
    production of pathogen-specific antibodies
  • This response is much stronger than the primary
    response and prevents any ill effects

20
HL Only Benefits and Dangers of Vaccines
  • Benefits
  • prevent disease and epidemics
  • results in a healthier society
  • reduces long-term medical costs
  • speed up the body's response to a future disease
    by memory B-cells
  • Dangers
  • possible allergic reactions
  • danger of side-effects

21
HIV and the Immune System
  • HIV virus kills Helper T-cells
  • Helper T-Cells tell B-cells there is a pathogen
  • Immune system cannot mount an effective defense
    against invading pathogens
  • Patients then succumb to secondary infections

22
Blood Clotting
  • Damaged cells in the blood vessel release
    compounds called clotting factors
  • These factors trigger the formation of the
    enzyme thrombin
  • Thrombin catalyzes the conversion of soluble
    fibrinogen in the blood to the fibrous protein
    fibrin
  • Fibrin forms threads which create an interwoven
    net
  • Platelets and blood cells get caught in the net
    and plug up the wound

23
Blood Clotting Diagram
24
1. Which is not true of active immunity? (1
mark)
IB Exam Question
  • A. It can be produced by exposure to a disease
    causing organism.
  • B. It can be produced artificially.
  • C. It can be produced by a virus.
  • D. It can be transferred via the colostrum.
  • Correct answer D
  • If youve never heard of it, its probably a
    trick question!

25
2. Describe how human skin and mucous membranes
act as barriers to pathogens.(4 marks)
IB Exam Question
  • To receive full marks, responses must have two
    answers for each.
  • Skin
  • lower pH / acid to keep bacteria from growing /
    chemical barrier
  • fatty acids / waxes antimicrobial
  • physical barrier to prevent entry / dry skin
    inhibits bacterial growths
  • bacteria on skin / mucous membranes prevent other
    bacteria from growing
  • antimicrobial / lysozyme in sweat and saliva
    (mucous membrane) to keep bacterial growth in
    check
  • Mucous membranes
  • mucous traps bacteria / sticky / mucus slightly
    acidic i.e. vagina
  • cilia sweep mucous up to be swallowed to kill
    bacteria
  • contain macrophages / phagocytes

26
3. Outline how phagocytic leucocytes ingest
pathogens in the blood and in body tissues.
IB Exam Question
  • The phagocytic cell surround the pathogen by
    endocytosis
  • A vacuole containing the pathogen travels to a
    lysosome and the membranes of the vacuole and
    lysosome fuse
  • Digestive enzymes in the lysosome destroy the
    pathogen
  • The pathogen debris is released by exocytosis

27
4. Which of the following represents the correct
sequence of events when the body is responding to
a bacterial infection?
(1 mark)
IB Exam Question
  • I. Antigen presentation by macrophages
  • II. Activation of B-cells
  • III. Activation of helper T-cells
  • A. I, II, III
  • B. I, III, II
  • C. III, II, I
  • D. II, III, I
  • Correct answer B

28
5. Explain antibody production.
IB Exam Question
  • A vaccine is injected into body
  • This vaccine contains killed / weakened pathogen
    or fragments of pathogens
  • Phagocytic leucocytes called macrophages ingest
    the pathogens and present the antigens from the
    pathogens on their cell surface.
  • Helper-T cells (another type of leucocyte that is
    specific to that antigen) bind to the antigen
    presented by the macrophages and are
    activated/stimulated
  • Meanwhile, B-cells bind to the antigen, and
    present the antigen as the T cells did
  • The activated T-helper cells then bind to B-cells
    and activate them
  • This triggers the B-cells to undergo mitosis to
    form memory cells and plasma cells
  • Short-lived Plasma B-cells secrete antibodies
    quickly that neutralize the pathogen
  • Memory B-cells stay in the blood for a long time
    and enable a more rapid response by the immune
    system if the same pathogen invades in the future

29
6. Which type of cell is responsible for
secondary immune responses to a pathogen?
(1 mark)
IB Exam Question
  • A. Cytotoxic T-cells
  • B. Phagocytes
  • C. Macrophages
  • D. Memory cells
  • Correct answer D

30
HL Only 7. Outline the principles of challenge
and response, clonal selection, and memory cells
as the basis of immunity.
IB Exam Question
  • B-cells make antibodies
  • The immune system can make 1015 different types
    of antibodies (but not all at once)
  • A few of each type of B-cell are produced and
    they wait until the body is infected with an
    antigen
  • When this occurs, they multiply to form many
    clones this is called clonal selection
  • A clone of B-cells can produces large amounts of
    antibodies quickly and give immunity to a
    disease, only after the immune system is
    challenged by a disease
  • This is called the challenge and response system

31
8. Which type of immunity usually results from
vaccination? (1 mark)
IB Exam Question
  • A. active, natural
  • B. active, artificial
  • C. passive, natural
  • D. passive, artificial
  • Correct answer B

32
9. Discuss the benefits and dangers of
vaccination.
(8 marks)
IB Exam Question
  • Benefits 5 max
  • prevent disease
  • eliminate diseases like smallpox
  • prevent epidemics
  • healthier society
  • reduce medical cost
  • disease free cattle / more food
  • Dangers 3 max
  • allergic reactions / anaphylactic shock
  • weakened virus becomes virulent / causes the
    disease
  • harmful side-effects

33
10. Which curve shows the response of the immune
system to a vaccine, followed by an infection?

(1 mark)
IB Exam Question
  • Correct answer B

34
HL Only 11. Describe the production of
monoclonal antibodies along with one use of them
in diagnosis and one use in treatment.
IB Exam Question
  • Monoclonal antibodies - large quantities of a
    single type of antibody, produced using the
    procedure outlined below.
  • 1. Antigens that correspond to a desired antibody
    are injected into an animal.
  • 2. B-cells producing the desired antibody are
    extracted.
  • 3. Tumor cells are obtained from another source
    (tumor cells grow and divide endlessly).
  • 4. B-cells are fused with tumor cells, producing
    hybridoma cells that divide endlessly, providing
    the desired antibodies.
  • 5. The hybridoma cells are cultured and
    antibodies they produce are extracted and
    purified.

35
HL Only 11. Describe the production of
monoclonal antibodies along with one use of them
in diagnosis and one use in treatment. cont.
IB Exam Question
  • Treatment of rabies
  • Rabies usually causes death in humans before the
    immune system can control it.
  • Injecting monoclonal antibodies when a person
    gets infected will control the virus and at the
    same time, the person's body begins making its
    own antibodies.
  • Diagnosis of malaria
  • 1. Monoclonal antibodies are made to bind to
    antigens in malarial parasites.
  • 2. A test plate is covered with antibodies.
  • 3. The sample to be tested is left on the plate
    long enough for malaria antigens (if present) to
    bind to antibodies.
  • 4. The sample is rinsed off and any bound
    antigens are detected using more monoclonal
    antibodies with attached color-changing enzyme.

36
12. Outline the effect of HIV on the immune
system.
IB Exam Question
  • The HIV virus results in the death of Helper
    T-cells
  • Therefore, the immune system of the infected
    individual cannot mount an effective defense
    against invading pathogens
  • Patients can then succumb to secondary infections

37
13. Describe the process of blood clotting.
IB Exam Question
  • Damaged cells in the blood vessel release
    compounds called clotting factors
  • These factors trigger the formation of the
    enzyme thrombin
  • Thrombin catalyzes the conversion of soluble
    fibrinogen in the blood to the fibrous protein
    fibrin
  • Fibrin forms threads which create an interwoven
    net. Platelets and blood cells get caught in the
    net and plug the open cut

38
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