Lifestyle factors that increase risk of
developing CHD
Poor diet - high intake of saturated fats or salt
Smoking
Lack of exercise
Leads to high blood pressure - damaging the heart and blood vessels
Excessive alcohol intake
Cancer
The result of uncontrolled cell division
Factors that increase the risk of many types of cancer
Smoking - mouth, throat and lung cancer
Excessive exposure to sunlight - skin cancer
Excessive alcohol intake - liver cancer
Pathogens
"An organism that causes a disease"
Types of pathogen
Fungi
Bacteria
Virus
Entry into the body
Gas exchange system
breathing in air containing pathogens (p)
p get trapped in mucus lining the
lung epithelium
cells have cilia that beat and move the mucus up the trachea to the mouth - where
removed
HOWEVER some pathogens are still able to reach the alveoli
where they can invade cells and cause damage
The skin
Damaged skin = pathogens on surface can enter bloodstream
Blood clots and dries, forming scab to prevent
pathogens from entering
HOWEVER some may get in before scab forms
Digestive system
Eat or drink something that contains pathogens
Most of them will be killed by acidic conditions of stomach
HOWEVER some may survive and pass into the
intestines where they invade cells of gut wall
How pathogens cause disease
Production of toxins
Cell damage
Done by...
Rupturing to release nutrients
Breaking down nutrients inside the cell for own use
Starves and eventually kills cell
Replicating inside the cell;
bursting them when they're
released
Immune Response
If a pathogen gets past your first line of defences, the
immune system kicks in
Activating the immune response
Pathogen invades body -> molecules on surface (antigens) are
identified as foreign -> activates cells in immune system
Antigens = a protein (or polysaccharide) that causes an immune response
ANTIbody GENerator
Four main stages of immune response
(1) phagocytosis
A phagocyte is a type of WBC that carries out the engulfment of
pathogens
Found in the bloody and in tissues and
are the first cells to respond to a
pathogen inside body
The phagocyte recognises the antigens on a pathogen
Cytoplasm of phagocyte moves round pathogen -- now contained in phagocytic vacuole
Lysosome fuses with the vacuole, releasing lysosomal enzymes which break pathogen down
phagocyte presents pathogen's antigens on its surface to activate other immune system cells
(2) T-cell activation
T-Cell = WBC
Has proteins on its surface that bind to
antigens presented by phagocytes, activating
T Cell
Different t-cells respond in different ways
Helper T Cells
activates B Cells
Killer T Cells
Destroy cell by attaching to antigens on pathogen
Suppressor T Cells
Stops the immune response (or it'll get out of
hand)
Memory Cells
(3) B-cell activation & plasma cell production
B-cell = WBC
covered with antibodies (that bind with antigens)
antigen-antibody complex
activates B-cell; which divides to
produce more b cells called plasma
cells (clones)
Memory Cells
remember specific antigen from primary response
bind to it second time around = immune; quicker and stronger response
(4) Antibody production
plasma cells secrete loads of antibodies
Functions
coating pathogen
making it easier for
phagocyte to engulf
it
coating it - preventing
it from entering host
cell
Binding &
neuatrisling
(inactivating)
toxins produced
by pathogen
Antibody structure
made up of chains of
amino acid monomers
linked by peptide bonds
Specificity of antibody depends on its variable
region (different shape due to different amino acid sequences)
Each antibody is
complementary to
one specific
antigen
Cellular response
T-cells
Humoral response
B-cells
Primary & secondary response
Primary
B-cells do their antibody thing and
eventually overcome infection
Secondary
memory cells produced from
primary response go go go
production of antibodies is quicker and greater
Vaccines
contain antigens that cause your
body to produce memory cells
against a particular pathogen,
without causing any disease
Immune
Herd immunity
fewer people to catch it from, so those not vaccinated are less likely to
catch the disease
The antigens are either free or attached to a dead or weakened pathogen
taken orally or injected
disadvantage for taking orally = can be broken down by
enzymes in the gut or molecules of vaccine may be too
large to be absorbed into the blood
Ethical issues
Tested on animals
Testing on people can
be risky
Some people don't want to take vaccine due to side
effects
but still protected due to herd immunity
some see this as being unfair
outbreak of a new disease - who would receive the vaccine first?
Antigenic Variation
some pathogens can change their surface antigens
(changes in the genes of a pathogen form different antigens)
memory cells produced from primary response do not recognise the antigens
Immune system starts from scratch
This takes time and so you get ill again
Hard to develop vaccines against pathogen
Influenza virus
Monoclonal Antibodies
they are antibodies produced from a single group of
genetically identical b-cells (plasma cells) - so identical in
structure
can make monoclonal antibodies that bind to anything you want - they will only bind to this target
molecule
Pregnancy tests, AIDS & anti-cancer drugs (pg 19-20)
Ethical issues
animal rights issues
Validating New Knowledge About
Vaccines and Antibodies
when a study presents evidence for a new theory it's important that other scientists
come up with more evidence to validate the theory i.e. repeat the study