Summary Notes designed for the International Baccalaureate Diploma Programme. These notes are detailed yet concise, with all the information to achieve a 7 in IB Biology HL or SL. These notes were made using information from the IB syllabus, Oxford IB Diploma HL Biology Textbook, Bioninja and the B...
Unit 11.1
• Every organism has unique molecules on the surface of its cells.
• A self-marker (MHC) labels the body’s nucleated cells so that they are tolerated by the immune
system.
• An antigen is recognised as foreign and provokes an immune response.
• Red blood cells do not have a nucleus, but do have
basic antigenic markers on their surface known as
glycoproteins.
• These are known as blood groups, which can be either
A, B, AB or O.
• As humans produce antibodies against foreign
antigens, blood transfusions are not always compatible
between certain blood groups.
• An additional glycoprotein (Rhesus factor) is either
present or absent, resulting in positive and negative
blood groups.
• Pathogens are usually species-specific (pathogenesis) and will only affect a certain species.
• However, some pathogens are not. Zoonoses are diseases from animals that can be transferred
to humans e.g rabies and influenza.
• See Unit 6 for Clonal Selection
• Once activated, B cells divide by mitosis into plasma cells and memory cells.
• Plasma cells are short-lived and secrete a high number of specific antibodies whereas memory
cells remain in the blood for years to provide long-standing immunity.
• Antibodies aid the destruction of pathogens in a number of ways:
• Making soluble antigens insoluble
• Clumping antigens together
• Masking dangerous parts of the antigen
• This makes it easier for the macrophage to ingest the pathogen.
• Immunity depends on the persistence of memory
cells.
• If a second infection with the same pathogen
occurs, memory cells will produce antibodies
quickly, meaning the pathogen does not have time
to cause symptoms.
• An allergen is something that provokes an immune
response despite not being harmful.
• An allergen provokes B cells to produce the antibody IgE, which attach to cells promoting the
release of histamines.
• Histamine release causes allergic symptoms by widening capillaries and increasing permeability,
causing heat and redness. This is known as an inflammatory response.
• Vaccines induce long-term immunity to specific pathogenic infections by stimulating the
production of memory cells. They come in different forms:
, • Weakened or inactivated pathogens which still have
antigens on their surface.
• Weakened toxins produced by a bacterial pathogen.
• Vaccines initiate the primary response, causing memory
cells to form.
• When exposed to the actual pathogen memory cells
trigger a secondary immune response that is much
faster and stronger, therefore little or no symptoms are
experienced.
• Smallpox was the first infectious disease in humans to
be eradicated via vaccination.
• The eradication was successful as smallpox was easily identifiable, transmitted by direct
contact only, and had a short-lived infection period.
• Monoclonal antibodies are antibodies that are artificially derived from a single B cell clone.
• An animal (mouse) is injected with an antigen causing it to produce specific plasma cells.
• These plasma cells are extracted and fused with tumour cells capable of endless divisions
forming a hybridoma cell. This cell can then synthesise large amounts of the antibody.
• This is used to make pregnancy tests:
• hCG is a hormone produced by pregnant women.
• Free monoclonal antibodies specific to hCG are conjugated to an enzyme that changes the
colour of a dye.
• If hCG is present in the urine, it will bind to the antibody and cause a strip of dye to appear
on the test.
Unit 11.2
• Synovial joints are capsules that surround the articulating surfaces of two bones (i.e. where the
bones connect).
• They consists of 3 main components: Joint capsule, cartilage and synovial fluid.
• The human elbow joint is a hinge joint, capable
of angular movement in one direction:
• Humerus: Anchors muscle
• Bicep: Bends to forearm
• Tricep: Straightens the forearm
• Joint Capsule: Seals joint space and limits
movement to provide stability
• Synovial Fluid: Provides food, oxygen and
lubrication to the cartilage
• Cartilage: Reduces friction and absorbs
shock
• Radius: Acts as a forearm lever for biceps
• Ulna: Acts as a forearm lever for triceps
• Muscles connect to bones (via tendons) and contract to provide the force required to produce
movement.
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