IB Biology 2015 Curriculum

1. Essential idea: The human body has structures and processes
that resist the continuous threat of invasion by pathogens.
6.3 and 11.1 Immune System HL Biology
The forgotten plague
By the dawn of the 19th century, the most deadly
killer in human history, tuberculosis, had killed one
in seven of all the people who had ever lived.

2. Understandings
Statement Guidance
6.3 U.1
The skin and mucous membranes form a
primary defense against pathogens that cause
infectious disease.
Diagrams of skin are not required.
6.3 U.2 Cuts in the skin are sealed by blood clotting.
6.3 U.3 Clotting factors are released from platelets.
6.3 U.4
The cascade results in the rapid conversion of
fibrinogen to fibrin by thrombin.
6.3 U.5
Ingestion of pathogens by phagocytic white
blood cells gives non-specific immunity to
diseases.
Subgroups of phagocyte are not required
6.3 U.6
Production of antibodies by lymphocytes in
response to particular pathogens gives
specific immunity.
Subgroups of lymphocyte are not required but
students should be aware that some lymphocytes
act as memory cells and can quickly reproduce to
form a clone of plasma cells if a pathogen carrying
a specific antigen is re-encountered.
6.3 U.7
Antibiotics block processes that occur in
prokaryotic cells but not in eukaryotic cells.
6.3 U.8
Viruses lack a metabolism and cannot
therefore be treated with antibiotics. Some
strains of bacteria have evolved with genes
that confer resistance to antibiotics and some
strains of bacteria have multiple resistance.

3. Applications and Skills
Statement Guidance
6.3 A.1
Causes and consequences of blood clot
formation in coronary arteries.
6.3 A.2
Florey and Chain’s experiments to test
penicillin on bacterial infections in mice.
6.3 A.3
Effects of HIV on the immune system and
methods of transmission.
The effects of HIV on the immune system
should be limited to a reduction in the number
of active lymphocytes and a loss of the ability
to produce antibodies, leading to the
development of AIDS.

4. Understandings
Statement Guidance
11.1 U.1
Every organism has unique molecules on the
surface of its cells.
11.1 U.2
Pathogens can be species-specific althoughothers
can cross species barriers.
11.1 U.3
B lymphocytes are activated by T lymphocytes in
mammals.
Limit the immune response to mammals.
11.1 U.4
Activated B cells multiply to form clones ofplasma
cells and memory cells.
11.1 U.5 Plasma cells secrete antibodies.
11.1 U.6 Antibodies aid the destruction of pathogens.
11.1 U.7
White cells release histamine in responseto
allergens.
11.1 U.8 Histamines cause allergic symptoms.
11.1 U.9 Immunity depends upon the persistence of memory
cells.
11.1 U.10 Vaccines contain antigens that trigger immunitybut
do not cause the disease.
11.1 U.11 Fusion of a tumour cell with an antibody-producing
plasma cell creates a hybridoma cell.
11.1 U.12 Monoclonal antibodies are produced byhybridoma
cells.

5. Applications and Skills
Statement Guidance
11.1 A.1
Smallpox was the first infectious diseaseof
humans to have been eradicated by vaccination.
11.1 A.2
Monoclonal antibodies to HCG are usedin
pregnancy test kits.
11.1 A.3
Antigens on the surface of red blood cellsstimulate
antibody production in a person with a different
blood group.
11.1 S.1
Analysis of epidemiological data relatedto
vaccination programmes.

6. Pathogens are disease causing organisms

7. Bacteria
• Prokaryotes (no real nucleus)
• Divide by binary fission
Can cause:
• Food poisoning (e.g. Salmonella)
• Ear and eye infections
• Cholera, diarrhea http://en.wikipedia.org/wiki/File:Ericson_Type_II_Conjunctivitis.JPG

8. The 1918 flu epidemic killed between 50 and 130 million
people. http://en.wikipedia.org/wiki/1918_flu_pandemic
Viruses
• Acellular (non-living?)
• Need a ‘host’ cell to carry out functions of life, including reproduction
• Can have DNA or RNA
• Mutate, evolve and recombine quickly
Cause:
• Flu, HIV/AIDS, smallpox, measles, common cold, ebola, herpes,

9. Fungi
• Eukaryotes, reproduce with spores
Cause:
• Athlete’s foot, mold, ringworm
• Allergic reactions and respiratory problems
Image from: http://en.wikipedia.org/wiki/Athlete's_foot

10. Protozoa
• Simple parasites
Cause:
• Malaria
• Leishmaniasis
• Toxoplasmosis
Leishmaniasis image from:
http://en.wikipedia.org/wiki/Leishmaniasis

11. Methods of disease transmission
Method of transmission Examples Types
Air Droplets in the air or dust Chicken pox
Water Contaminated water Typhoid
Food Contaminated food Food poisoning
Insect/Animal Mosquito Malaria
Sexual Sexual intercourse HIV
Touch (Direct Contact) Skin or saliva Polio

12. Defense Mechanisms
• Defense can be non-specific or specific (B cells and T cells)
• Non-specific mechanisms provide a general barrier to infection
and is the first line of defense.
Immune System defense against pathogens

13. 6.3 U.1 The skin and mucous membranes form a primary defense against pathogens
that cause infectious disease.
Mucous membrane
• Sticky trapping invaders
• pH that is not favorable to
pathogens
• Lysozyme an enzyme that
breaks down pathogens
• Symbiotic organism that aid in
or protection
Skin
• A continuous structure
without many openings
• Multiple layers
• Dry
• pH levels that are unfavorable
to pathogens
• Lysozyme an enzyme that
breaks down pathogens
• Symbiotic organism that aid in
or protection
1st Line of Defense (non specific)

14. 6.3 U.1 The skin and mucous membranes form a primary defense against pathogens
that cause infectious disease.

15. 6.3 U.2 Cuts in the skin are sealed by blood clotting. 11.1 U.2 Pathogens can be species-
specific although others can cross species barriers.
• Wounds such as cuts to the skin causes opening through which pathogens can potentially
enter the body
• Blood clots at the site of a wound to prevent blood loss and the entry of pathogens.
• Platelets (small cell fragments) along with damaged tissue release clotting factors in
response to a wound.
• Clotting factors cause a series of reactions which end with fibrin (a protein) fibers forming
a mesh across the wound site
• The fibrin fibers capture blood cells and platelets forming a clot. In the presence of air the
clot dries to form a scab with shields the healing tissues underneath

16. Clotting Mechanism
a) Platelets or damaged cells are
stimulated to release a group of
proteins called clotting factors.
These clotting factors are released
into the plasma at the wound site
b) Clotting factors activate the
enzyme Thrombin from its inactive
form prothrombin
c) Thrombin turns the soluble
plasma protein fibrinogen into its
insoluble fibrous form Fibrin
d) Fibrin binds together platelets
and blood cells to form a solid
'plug' for the wound. This plug is
called a clot
U.3 Clotting factors are released from platelets.

17. ClottingArteriosclerosis
• Occlusions in an arterial wall are cause by a
hardening and thickening of the walls of the
arteries.
• The condition can occur because of fatty
deposits on the inner lining of arteries
(atherosclerosis).
• Calcification of the wall of the arteries, or
thickening of the muscular wall of the
arteries from chronically elevated blood
pressure occurs.
• As the deposits of fat and plaque begin to
build the lumen of the arteries become
reduced. If the plaque frees itself from the
wall a blood clot may form. This may lead
to coronary thrombosis (reduced blood
flow to the heart).
• When coronary arteries that supply blood
to the heart muscle are effected a shortage
of oxygen delivered to the heart itself may
lead to a heart attack.
6.2 A.3 Causes and consequences of occlusion of the coronary arteries.
6.3 A.1 Causes and consequences of blood clot formation in coronary

18. • Ingestion of a smaller cell or cell fragment, a microorganism, or foreign
particles.
• These cells fold around the pathogen until it has been surrounded and
engulfed by closure of the membrane and formation a vacuole.
Phagocytosis (white blood cells/leukocyte)
2nd Line of Defense (non specific)
6.3 U.5 Ingestion of pathogens by phagocytic white blood cells gives non-
specific immunity to diseases.

19. 6.3 U.5 Ingestion of pathogens by phagocytic white blood cells gives non-
specific immunity to diseases.

20. 11.1 U.8 Histamines cause allergic symptoms.
Histamine is a second line non-specific defense: consisting
of small organic molecules produced by two types of leukocyte: basophils
and mast cells
The lose of fluid from capillaries into the surrounding tissue cause
the response symptoms:
Inflammation / hives
Itching
Sneezing
Watery eyes

21. 11.1 U.7 White cells release histamine in response to allergens.
Allergies are a group of conditions caused by hypersensitivity of the
immune system to something in the environment that causes little or no
problem in most people. The result is a unneeded release of histamines. This
can cause any of the following: Inflammation / hives, Itching, sneezing and
watery eyes. People with allergies often take anti-histamines to counter there
immune systems response

22. The Specific Immune Response
http://life9e.sinauer.com/life9e/pages/42/422003.html
http://highered.mheducation.com/sites/0
072507470/student_view0/chapter22/ani
mation the_immune_response.html
http://web.biosci.utexas.edu/psaxena/MicrobiologyA
nimations/Animations/HumoralImmunity/micro_hu
moral.swf

23. Lymphocytes
• Is a response designed for a specific pathogen antigens.
There are 2 types of lymphocytes.
1. B cells
2. T cells
3rd line of defense (Specific)
11.1 U.3 B lymphocytes are activated by T lymphocytes in mammals

24. 6.3 U.6 Production of antibodies by lymphocytes in response to particular pathogens
gives specific immunity. 11.1 U.1 Every organism has unique molecules on the surface of
its cells
http://www2a.cdc.gov/nip/isd/ycts/mod1/courses/genrec/images/10110g1.jpg
https://edc2.healthtap.com/ht-staging/user_answer/reference_image/7600/large/Antigen.jpeg?1386669177
• An organism recognizes surface molecules present on it’s own cells, therefore unfamiliar
surface molecules are regarded as foreign and provoke a specific immune response
(antibody production).
• The surface of an organisms’ cells are covered in uniquely shaped molecules, examples
include the polysaccharides of a bacterium’s cell wall and the glyco- proteins embedded in
the plasma membrane of a eukaryote. The protein coat (capsid) of a virus also contains
uniquely shaped molecules.
An organism recognizes surface molecules present on it’s
own cells, therefore unfamiliar surface molecules are
regarded as foreign and provoke a specific immune
response (antibody production).
Unfamiliar surface molecules that cause the
production of antibodies are called antigens.

25. Antigen
• An antigen is any
molecule that is foreign
such as bacteria,
viruses, protozoans,
worms, etc. Example:
Blood cells
Antibody
• A protein the
recognizes specific
antigens and binds
to it as par of an
immune response
6.3 U.6 Production of antibodies by lymphocytes in response to particular pathogens
gives specific immunity. 11.1 U.1 Every organism has unique molecules on the surface of
its cells

26. Review: 3.4 A1 Inheritance ofABO blood groups. AND 11.1 A.3Antigens on the surface of red blood cells stimulate
antibody production in a person with a different bloodgroup.
The ABO blood type classification system uses the presence or absence of certain
antigen on red blood cells to categorize blood into four types.
Distinct molecules called agglutinogens (a type of antigen) are attached to the surface of red
blood cells. There are two different types of agglutinogens, type "A" and type "B”.
http://www.ib.bioninja.com.au/_Media/abo_blood_groups_med.jpeg
http://www.anatomybox.com/tag/erythrocytes/

27. A Nobel breakthrough in medicine.
Images and more information from:
http://learn.genetics.utah.edu/content/begin/traits/blood/
Blood type O is known as the universal donor, as it has no
antigens against which the recipient immune system can
react. Type AB is the universal recipient, as the blood has
no antibodies which will react to AB antigens.
Blood typing game from Nobel.org:
http://nobelprize.org/educational/medicine/landsteiner/readmore.html
More about blood typing
Antibodies (immunoglobulins) are specific to antigens. The
immune system recognises 'foreign' antigens and produces
antibodies in response - so if you are given the wrong
blood type your body might react fatally as the antibodies
cause the blood to clot.
Review: 3.4 A.1 Inheritance of ABO blood groups. AND 11.1 A.3Antigens on the surface of red blood cells
stimulate antibody production in a person with a different bloodgroup.

28. Recognition (First step)
• an infected cell will display antigens on its surface
• Non specific White blood cell recognize the
pathogens antigen makers.
• WBC’s engulf a pathogen, dissolves it and present
the antigen mark to T cells, trigger immune
response
11.1 U.3 B lymphocytes are activated by T lymphocytes in mammals
Macrophage (WBC)

29. T cells play a central role in immunity. They release a chemical interleukin. This
chemical activate Killer T cells and B Cells (which release antibodies)
11.1 U.3 B lymphocytes are activated by T lymphocytes in mammals

30. • Once stimulated by T-
cells, B-cells bind to
infected cell antigens
• B Cells differentiate
into plasma cells in the
bone marrow.
• Plasma cell being
rapidly producing
antibodies against the
pathogen antigen.
• Antibodies stay in
blood to prevent future
infection.
11.1 U.4 Activated B cells multiply to form clones of plasma cells and memory cells.
11.1 U.5 Plasma cells secrete antibodies.

31. A) Plasma cells synthesis
antibodies
B) The antibody binds them
to other antigen
C) Makes it easier for the
Antigen(A) to be engulf
by phagocytic and digest
it
6.3 U.6 Production of antibodies by lymphocytes in response to particular pathogens
gives specific immunity. 6.3 U.6 Production of antibodies by lymphocytes in response to
particular pathogens gives specific immunity.

32. 6.3 U.8 Viruses lack a metabolism and cannot therefore be treated with antibiotics. Some strains of
bacteria have evolved with genes that confer resistance to antibiotics and some strains of bacteria
have multiple resistance.

33. The discovery of penicillin.
http://wellcomelibrary.org/player/b16778868#?asi=0&ai=0
For their work on penicillin Fleming, Florey and Chain were awarded the Nobel prize
for medicine in 1945
Discuss the ways in which Florey and Chain’s work is accord with
and breaches the modern practices of drug testing.
6.3 A.2 Florey and Chain’s experiments to test penicillin on bacterial infections in mice.
AND Nature of science: Risks associated with scientific research - Florey and Chain’s
tests on the safety of penicillin would not be compliant with current protocol on testing.
(4.8)

34. 6.3 U.8 Viruses lack a metabolism and cannot therefore be treated with antibiotics.
Some strains of bacteria have evolved with genes that confer resistance to antibiotics
and some strains of bacteria have multiple resistance.
Virus
• Viruses are protected by the
host cell structure
• Viruses have a very different
structure to prokaryote, just a
protein capsid and genetic
material - no cell wall or
membrane to attack
• Viruses use the (eukaryotic)
host cell metabolism
Bacteria and Fungi:
• cell walls and membranes
• Protein synthesis (translation)
• DNA/RNA synthesis
• Other metabolic processes (e.g.
enzyme function)

35. Antibiotics are drugs used in the treatment and
prevention of prokaryotic bacteria
• Eukaryote (e.g. human) cells
have different structure and
function then do prokaryotes.
Therefore drugs that inhibit
prokaryotes often have little
or no effect on eukaryotes
• Antibiotics are designed to
disrupt structures or
metabolic pathways in
bacteria and fungi because of
their are different cell
structure
• In viruses, these do not
exist or are very different, so
antibiotics have no effect
upon them.
6.5.U7 Antibiotics block processes that occur in prokaryotic cells but not in eukaryotic
cells. AND 6.3.U8 Viruses lack a metabolism and cannot therefore be treated with
antibiotics.

36. 5.2 A.2 Evolution of antibiotic resistance in bacteria.
• An example of evolution by natural selection
• Bacteria mutate and resistance to an antibiotic naturally arises
• Bacteria divide rapidly therefore a resistant strain of bacteria
can quickly proliferate
• Over time strains of bacteria can become resistant to multiple
strains of bacteria
Indiscriminate use of antibiotics is leading to antibiotic resistance in
bacteria

37. 5.2 A.2 Evolution of antibiotic resistance in bacteria.

38. 5.2 A.2 Evolution of antibiotic resistance in bacteria.

39. Causes of Antibiotic Resistance
Over-prescribing of antibiotics
Poor Infection control in hospitals and clinics
Patients not finishing their treatment
Lack of hygiene and poor sanitation
Over use of antibiotics in livestock and fish farming
Lack of new antibiotics being developed
6.3 U.8 Viruses lack a metabolism and cannot therefore be treated with antibiotics. Some strains of
bacteria have evolved with genes that confer resistance to antibiotics and some strains of bacteria
have multiple resistance.

40. 6.3 A.2 Florey and Chain’s experiments to test penicillin on bacterial infections in mice.
AND Nature of science: Risks associated with scientific research - Florey and Chain’s
tests on the safety of penicillin would not be compliant with current protocol on testing.
(4.8)
Modern process of drug testing and clinical trials
• Years of extensive laboratory research on animals and
human cells to determine usefulness, likely dosage and
possible side-effects
• Assess the safety of the drug and the impact of side-
effects on a small group of healthy volunteers – starting
with a small dosage which is slowly increased
• Test the effectiveness of the drug against a control on a
small group of affected volunteers
• Randomized and blind testing on a large group of
affected volunteers against a placebo and competing
drugs

41. Modern medicine would consider Jenner’s testing procedure unethical:
• no prior research had be done prior to human testing to determine the
effectiveness and possible side-effects
• informed consent was not given and the choice of a child who was to young to understand
the dangers was even more questionable
• Cowpox is a mild viral infection of cows, which
is very similar to smallpox
• In 1796 Edward Jenner deliberately infected an
eight-year old boy with cowpox from
pocks/blisters of a milkmaid with this disease.
• Jenner then attempted to infect the boy with
smallpox, but found that he was immune.
Jenner repeated his initial on himself
and a small group of people
11.1 U.10 Vaccines contain antigens that trigger immunity but do not cause the disease.11.1 U.9 Immunity depends upon the
persistence of memorycells.
Nature of science: Consider ethical implications of research - Jenner tested his vaccine for smallpox on a child. (4.5)

42. 11.1 U.10 Vaccines contain antigens that trigger immunity but do not cause the disease.AND 11.1.U9 Immunity
depends upon the persistence of memory cells.
Vaccination allows an individual to become immune to a disease without experiencing it.

43. Vaccination allows an individual to become immune to a disease without experiencing it.
11.1 U.10 Vaccines contain antigens that trigger immunity but do not cause the disease.
11.1 U.9 Immunity depends upon the persistence of memory cells.

44. 11.1 A.1 Smallpox was the first infectious disease of humans to have been eradicated by vaccination.
This was achieved by a
worldwide vaccination
programme. 1977 saw
the last ever naturally
occurring case of the
disease in Somalia and in
1980 the World Health
Organisation (WHO)
declared the disease
‘dead’.
Erradication programmes for other diseases has reduced the number of cases, but has
been less successful:
• Polio and measles become contagious before symptoms are easy to detect
• Immunity to Malaria is not complete and hence it can infect the same person a
number of times
• Yellow fever has an animal reservoir, it can also affect monkeys
Smallpox (caused by the virus variola) was the first infectious disease of humans to
have been eradicated by vaccination.
http://www.mus
eumofhealthcar
e.ca/images/exh
ibits/vaccination
s/smallpox/large
/17.jp

45. 11.1 U.11 Fusion of a tumour cell with an antibody-producing plasma cell creates a hybridoma cell. AND11.1 U.12
Monoclonal antibodies are produced by hybridomacells.
Production of monoclonal antibodies: When an immune response occurs,
antibodies specific to the pathogen are produced. By capture plasma cells containing
antibodies of that pathogen. Plasma cells are fused with tumor cells to produce larger
numbers of the antibodies to be used for therapeutic treatments or testing
1. An animal (often a mouse)
is injected with an antigen
and in response produces
specific plasma cells
2. The plasma cells are
harvested from the spleen
of the animal
3. Harvested plasma cells
fused with tumor cells
(which are capable of
endless divisions) forming
a hybridoma cells
4. The hybridoma cells are screened
to determine which onesare
producing useful antibodies
5. The selected hybridoma is allowed to divide to produce clones
6. Hybridomas are then used to synthesise large quantities of a single (monoclonal)
antibodies for use in diagnostic tests and treatment

46. 11.1 A.2 Monoclonal antibodies to HCG are used in pregnancy testkits.
Pregnancy tests use monoclonal antibodies
https://youtu.be/QuN0Z65sp5c
http://www.sumanasinc.com/webcontent/animations/content/pregtest.html
http://ed.ted.com/lessons/how-do-pregnancy-tests-
work-tien-nguyen
Use the animations to find out how they work

47. 11.1 U.2 Pathogens can be species-specific although others can cross species barriers
• Some pathogens are species-specific. Polio, Measles and Syphilis only
affect humans.
• However many others such as Flu, Aids, Ebola and Salmonella can be
transmitted between humans and other animals. A zoonosis is any disease
or infection that is naturally transmissible from vertebrate animals to
humans.

48. HIV
• A retrovirus responsible for causing
AIDS.
• AIDS is an autoimmune disease.
• Causes a reduction in the
number of active lymphocytes.
• Causes a loss in ability to produce
antibodies.
• There is currently no cure for HIV.
However, with the right treatment
and support, people can live long
and healthy lives.
6.3 A.3 Effects of HIV on the immune system and methods of transmission.

49. Bibliography / Acknowledgments