OCR Biology 2.2 Notes. Disease and the Immune Response

Here are some fairly detailed notes on disease, the immune response and a few other points covered in the specification of F212 module 2 topic 2.

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  • Created on: 11-05-12 16:20
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F212 Biology Notes
Parasite ­ organisms that live in or on another living thing, harming their host, usually by
taking their nutrients. External parasites live on the host, e.g. head lice, and internal parasites
live inside the host, e.g. tapeworm.
Pathogens ­ pathogens are organisms that cause disease, taking nutrients from the host
while also causing damage in the process.
Malaria ­ Plasmodium, a protoctista. Carried by a vector; the female Anopheles mosquito.
The mosquito sucks the blood of an infected person, and the parasite gametes fuse and
form zygotes. They then migrate to the salivary glands of the mosquito, and when this
mosquito bites an uninfected person, a little saliva is injected as an anticoagulant. The
malarial parasite then passes through the blood to the liver, where they multiply before
entering the blood once again
HIV/AIDS ­ Caused by the human immunodeficiency virus. Can remain inactive in the body for
a long period of time, but when it becomes active it attacks and destroys T helper cells. This
weakens the immune system, and a range of opportunistic infections may strike. AIDS is the
latter stages of the disease, and this stands for acquired immune deficiency syndrome.
Transmitted by unprotected sex, blood to blood contact, unscreened blood transfusions,
use of unsterile surgical equipment, sharing hypodermic needles, across the placenta and
during breast feeding
TB ­ caused by Mycobacterium tuberculosis, transmitted by droplet infection, by sneezing.
Spreads easily if conditions are overcrowded with poor ventilation, poor health, poor diet
and homelessness
Immune response ­ The specific response to a pathogen, which involves the action of
lymphocytes and the production of antibodies
Antigen ­ molecules which stimulate an immune response
Antibody ­ protein molecules that can identify and neutralise antigens
Variable Region
Constant Region

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Antibodies consist of:
Four polypeptide chains held together by disulfide bridges
A constant region, which allows the antibody to attach to phagocytic cells and helps
in the process of phagocytosis
A variable region, which is complementary to a specific antigen
Hinge region, which allows some flexibility, so the branches can move further apart
to allow attachment to more than one antigen
Mode of action of antibodies
The variable region of the antibody binds to a pathogen's antigens, neutralising the
pathogen, as the antigens will have…read more

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T helper cells ­ release cytokines that stimulate the B cells to develop and
stimulate phagocytosis by the phagocytes
T killer cells ­ attack and kill infected body cells, by releasing hydrogen peroxide
(toxic) into the cells
T memory cells ­ give immunological memory
B cells ­ differentiate into plasma cells or B memory cells
Plasma cells ­ circulate around the body releasing antibodies
B memory cells ­ remain in the body for a number of years and act as
immunological memory
T lymphocytes…read more


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