Communicable diseases, disease prevention and the immune system Flashcards
what is a pathogen?
Microorganism that causes disease
Lives in hosts
what is a communicable disease?
Any disease transmitted from one person or animal; contagious
4 groups of microorganisms
Bacteria
Fungi
Viruses
Protoctista
Diseases caused by bacteria
Tuberculosis
Bacterial meningitis
Ring rot in plants
Diseases caused by viruses
HIV/ AIDS
Influenza
Tobacco mosaic virus
Diseases caused by fungi
Black sigatoka
Ringworm
Athletes foot
Diseases caused by protoctista
Malaria
Potato/ tomato blight
Prokaryotic pathogens
Bacteria
Eukaryotic pathogens
Fungi
How do bacteria damage hosts?
Multiply rapidly
Damage cells by releasing waste products and/or toxins
How do fungi damage hosts?
Hyphae release extracellular enzymes e.g. celluloses to digest plant tissue
Causes decay and leaf death —> no photosynthesis
May produce toxins
Are viruses eukaryotic or prokaryotic?
Neither; they’re dead
How do viruses damage hosts?
Invade living cells where genetic material in virus takes over the biochemistry of the host cells
Makes more copies
Host cell bursts, releasing viruses
what are Bacteriophages?
Viruses that can attack bacteria
How do protoctista damage hosts?
Enter host cells and feed on contents before breaking over cells
How may protoctista enter through the body directly?
Polluted water
what is Transmission?
Passing a pathogen from an infected individual to an uninfected individual
what is Direct transmission?
Passing a pathogen from host to new host, with no intermediary
what are types of direct transmission?
Physical contact: touching an infected person
Touching contaminated surfaces
Exchanging bodily fluids
Faecal - oral transmission: eating food or drinking water contaminated by pathogen
Droplet infection: pathogens are carried in tiny water droplets in the air
Spores: are the resistant stage of some pathogens
Can be carried in the air or reside on surfaces or in the soil
what is Indirect transmission?
Pathogens are transmitted indirectly via a vector
what is a Vector?
Another organism that may be used by the pathogen to gain entry to the primary host
what is a cause of malaria?
Plasmodium parasite
It enters the human host via a bite from a female Anopheles mosquito
what social factors affect direct transmission?
Overcrowding Poor ventilation Poor sanitation Poor health - likely to contract other diseases Poor diet (malnutrition) Lack of education
Why is there a greater variety of diseases to be found in warmer climates?
Many protoctists, bacteria and fungi can grow and reproduce more rapidly in warm and moist conditions
Why are plants targets for microorganisms?
Manufacture sugars in photosynthesis and convert this into wide variety of compounds such as proteins and oils - rich source of nutrients for microorganisms
how is the skin a primary, non-specific defence?
physical/ chemical barrier
secretes sebum- creates acidic environment so pathogens cant colonise
secrete lysozymes- catalyses the breakdown of carbohydrates in cell walls of bacteria
describe mucus membranes
pathogens breathed in get trapped in mucus lining the lung epithelium
cilia wafts the mucus up the trachea to the throat- swallowed and goes to stomach where its killed
what happens during blood clotting?
they’re formed by series of chemical reactions that take place when platelets are exposed to damaged blood vessels
what happens during inflammation?
swelling
pain
heat
redness
histamines released by mast cells in injured tissue cause vasodilation
which increases the flow of blood to the infected area and increases permeability of
blood vessels.
antibodies, white blood cells and plasma leak out
into the infected tissue and destroy the pathogen
What are cytokines?
produced in Mast cells
Cell-signalling molecules that are produced in damaged tissues that attract phagocytes to the site of infection/inflammation
What are histamines?
produced in the mast cells
Chemicals that make blood vessels dilate and the blood vessel walls leaky
What are interleukins?
A type of cytokine produced by helper T cells
What are antibodies?
Y-shaped glycoproteins made in the B cells in response to the presence of an antigen
What are B lymphocytes?
Lymphocytes which mature in the bone marrow and that are involved in the production of antibodies
What are autoimmune diseases?
Diseases that are the result of abnormal immune responses that attack normally present tissues
What are B effector cells?
B lymphocytes that divide to form plasma cell clones
What are killer T cells?
T lymphocytes that destroy pathogens carrying a specific antigen with perforin
What are antigen-antibody complexes?
The complex formed when an antibody binds to an antigen
What are T regulator cells?
T lymphocytes that suppress and control the immune system, stopping the response once a pathogen has been destroyed and preventing an autoimmune response
What are antigen-presenting cells?
A cell that displays foreign antigens complexed with MHC complexes on their surfaces
What are Phagosomes?
The vesicle in which a pathogen or damaged cell is engulfed by a phagocyte
What are T lymphocytes?
Lymphocytes which mature in the thymus gland and that both stimulate the B lymphocytes and directly kill pathogen
what happens during wound repair?
skin reforms barrier
cells divide and migrate to edges of wound
tissues below wound contract to bring edges closer
repaired using collagen fibres
what happens when you have too many collagen fibres?
you end up with a scar
what are expulsive reflexes?
coughing
sneezing
expel foreign objects including pathogens
automatic
what are plant physical defences?
waxy cuticle
cell walls
callose deposited between plant cell and plasma membrane - limit virus spreading/ harder to enter cells
what are plant chemical defences?
saponins- destroy cell membranes of pathogens
phytoalexins- inhibit growth of pathogens
How do antibodies defend the body? (4 reasons)
- Act as opsonins so the antigen is ‘tagged’ and easily engulfed
- Act as antitoxins, binding to toxins produced by pathogens to render them harmless
- Cause agglutination (clumping together) of pathogens which have antigen-antibody complexes, preventing them from spreading through the body and makes it easier for phagocytes to engulf several pathogens at once
- Prevents pathogens from effectively invading a host
What is a specific immune response?
The immune system ‘remembers’ an antigen after an initial response leading to an enhanced response to subsequent encounters
How does the sequence of amino acids affect an antibody?
The sequence of amino acids determines the shape of the variable region (sequence of amino acids) and so which antigen is detected
How many polypeptide chains does an antibody contain?
4
What type of protein is an antibody?
globular
How many binding sites are there on an antibody?
Where are they?
Two antigen binding sites
One receptor site that allows the body to recognise the antibody as self
What type of bonding occurs between the heavy and light strands in antibodies?
Disulfide
Why do antibodies have a hinge?
Allows antibodies to flex slightly and accommodate differently sized antigens
what happens during phagocytosis?
Neutrophils Macrophages recognises antigen cytoplasm move around it and engulfs it easier in presence of opsonins- tag it pathogen contained in phagosome lysosome fuses with phagosome- enzymes break it down macrophage presents antigens on surface with MHC- makes antigen-presenting cell
what happens during T-lymphocyte activation?
Each T lymphocyte has a receptor on its surface
Receptor meets a complimentary antigen
Activates the T lymphocyte (clonal selection)
It divides to produce clones of itself (clonal expansion)
Different T lymphocytes carry out different functions:
T helper- release substances to activate B lymphocytes and T killer
T killer- attach and kill cells that are infected with a virus
T regulatory- supress immune response from other WBC- stops immune system attacking body cells
some activated T lymphocytes become memory cells
what happens during B lymphocyte activation?
B lymphocytes covered in antibodies
each has a different shape antibody on membrane- to bind to different shape antigens
binding and substances released by T helper activate B lymphocyte- clonal selection
B lymphocyte divides by mitosis into plasma and memory cells- clonal expansion
what happens during antibody production?
plasma cells are clones of B lymphocyte
secrete loads of antibody, specific to antigen, into the blood
antibodies bind to the antigen on surface of the pathogen to form antigen- antibody complexes
signal for immune system to attack and destroy pathogen
identify each cell in a blood smear
neutrophil- multi lobed nucleus, grainy cytoplasm
lymphocyte- smallest, nucleus takes up most of cell
monocyte- biggest, kidney- bean shaped nucleus, non-grainy cytoplasm
what happens during the secondary immune response?
pathogens enter body again, immune system produces quicker stronger immune response
clonal selection is faster. B lymphocytes divide into plasma and produce right antibody
memory T lymphocytes activated and divide to kill cell carrying antigen
no symptoms
how do you maintain immunity?
memory T and B lymphocytes have short lifespan
immunity may go
maintain by constantly being exposed to pathogen to make more T and B memory
what is active and passive immunity?
ACTIVE- immune system makes own antibodies:
natural- immune after catching disease
artificial- immune after getting vaccination
PASSIVE- given antibodies made by different organism:
natural- baby is immune from mothers antibodies
artificial- immune after injected with someone elses antibodies
how do vaccines work?
contain antigens that cause body to produce memory cells
antigens attached to dead or weakened pathogen
become immune without getting symptoms
injected or taken orally
disadvantage of oral is it could be broken down by enzymes in gut or might be too big for absorption
booster vaccines are given later on
name all the routine vaccines
MMR- measles, mumps, rubella. 1 year old and again before starting school
meningitis C- protects against that bacteria. 3 months then booster given to 1 yr old and teens
why do we change vaccines regularly?
pathogens change surface antigens
vaccines no longer work
immune system starts again and carries out primary immune response
e.g. influenza
what are antibiotics?
chemicals that kill or inhibit growth of bacteria
treat bacterial infections
what are the problems with antibiotic resistance?
genetic variation in bacteria
mutations make bacteria resistant to antibiotics
able to survive in a host treated with antibiotic
lives longer and reproduces
leads to the allele for antibiotic resistance being passed (natural selection)
how can we overcome antibiotic resistance?
developing new antibiotics and modifying existing ones
doctors are being encouraged to reduce their use of antibiotics
patients advised to take all antibiotics to make sure all bacteria is killed
what are different sources of medicine?
plants, animals, microorganisms
penicillin obtained from fungus
cancer drugs made using soil bacteria
daffodils produce drug used to treat Alzheimers
future of medicine
personalised medicine:
tailored to an individuals DNA
doctors use your genetic info to predict how you will respond to drugs and prescribe the most effective ones
synthetic biology:
using technology to design artificial proteins, cells and microorganisms
