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diseases and immunity

Terms in this set (51)

Define the term pathogen. (2)
A microorganism
That causes a disease
For tuberculosis, state the organism it affects and the pathogen
Animals
Bacterium
For bacterial meningitis, state the organism it affects and the pathogen
Humans
Bacterium
For ring rot, state the organism it affects and the pathogen
Potatoes, tomatoes
Bacterium
For HIV/AIDs, state the organism it affects and the pathogen
Humans
Virus
For influenza, state the organism it affects and the pathogen
Animals
Virus
For TMV, state the organism it affects and the pathogen
Plants
Virus
For black sigatoka, state the organism it affects and the pathogen
Banana plants
Fungus
For ringworm, state the organism it affects and the pathogen
Cattle
Fungus
For athlete's foot, state the organism it affects and the pathogen
Humans
Fungus
For potato/tomato late blight, state the organism it affects and the pathogen
Potatoes & Tomatoes
Protoctists
For malaria, state the organism it affects and the pathogen
Animals
Protoctists
Define the term direct transmission and state two examples. (3)
When a pathogen is transmitted directly from one organism to another.
Droplet infection - coughing or sneezing
Sexual contact
Define the term indirect transmission and state four examples. (5)
When a pathogen is transmitted from one organism to another via an intermediate.
Air
Water
Food
Vector (another organism)
State three factors, linked to living conditions, which can increase the rate of transmission of pathogens. For each one give an example. (3)
Overcrowded conditions - any pathogen spread by droplet infection
Climate - The mosquitos that carry the malarial parasite breed more quickly in hot and humid conditions
Social factors - The HIV pathogen is spread more quickly in countries with limited access to barrier contraception
Describe three physical defences plants have to prevent pathogens entering. (3)
Waxy cuticle - physical barrier against pathogens entering
Cellulose cell walls - prevent the pathogen moving from cell to cell
Callose - a polysaccharide deposited between plant cell walls during stress
Describe three chemical responses plants have to either prevent pathogens entering, or to destroy them if they have entered the plant. (3)
Saponins - destroy the cell membrane of fungal pathogens
Phytoalexins - inhibit the growth of fungal pathogens
Toxins - prevent insects feeding and therefore reduces the risk of infection by pathogens carried by the insects
Describe the difference between active and passive immunity
Active - the immune system makes antibodies
Passive - antibodies are given, the body does not make them
What type of immunity is does a vaccination give?
Active artificial
What type of immunity does antibodies in breast milk give?
Passive natural
What type of immunity does getting the chickenpox pathogen enters you which you are immune in the future give?
Active natural
What type of immunity does an injection of antibodies give?
Passive artificial
What type of immunity does antibodies crossing the placenta give?
Passive natural
Explain how a vaccination gives you long term immunity against a pathogen
A vaccine contains the antigens of the pathogen
Clonal selection occurs of the complementary B and T lymphocytes
Differentiation occurs
Memory B and T lymphocytes are produced
The memory cells stay in the blood
If the pathogen enters your blood naturally
The memory cells can differentiate quickly
Lots of antibodies are produced quickly
You don't get any symptoms of the disease
Explain how vaccination programmes can prevent disease epidemics
This is called herd immunity
If most people are vaccinated the disease becomes extremely rare
The people who aren't vaccinated are also protected
Explain why the flu vaccine has to be changed every year
The flu virus has a high rate of mutation
Therefore the antigens on the surface change rapidly
And there are lots of strains of the virus
New vaccines are developed each year
The vaccine that is most effective against the current strain is used
Describe what is meant by an auto immune disease
The immune system recognises antigens in the body as foreign
There is an immune response against the body's tissues
State 2 examples of autoimmune diseases. For each one describe the symptoms
Lupus
Immune system attacks cells in the connective tissue
Causes inflammation
Rheumatoid arthritis
Immune system attacks the joints
Causes pain and inflammation
State two possible sources of new drugs
Plants
Microorganisms
Linked to finding new drugs, explain why it is important that we maintain biodiversity
Only a small proportion of plants and microorganisms have been studied
If we don't maintain biodiversity, species could become extinct before we find any useful compounds in them.
Explain why antibiotics are useful
Antibiotics kill bacteria
Therefore, they are used to treat bacterial infections
Since the mid 20th century
For example penicillin
Describe how bacteria can become resistant to antibiotics
A random DNA mutation makes some of the bacteria resistant to the antibiotic
When the antibiotic is taken the bacteria that are not resistant die
Only the resistant bacteria are left
They reproduce asexually
And pass on the allele for the resistance
The allele frequency increases
And eventually the whole population if bacteria is resistant
State the names of two bacteria that show antibiotic resistance. For each one state the part of the body that it infects
MRSA (methicillin resistant Staphylococcus aureus)
Infects wounds
Clostridium difficile
Infects the digestive system
Describe what is meant by personalised medicines
Different people respond to drugs in different ways
Because of the genes they have
Personalised medicines are matched to a person's DNA
Therefore doctors can ensure that patients take the drug that will be the most effective
Describe what is meant by synthetic biology
Using technology
To design and make biological structures
For example proteins, cells or microorganisms
These could then be used as drugs
DDraw a labelled diagram of an antibody
Describe the function of the variable region
Form the antigen binding sites.
Different in each antibody.
Specific to the antigen.
Describe the function of the hinge region
Allows flexibility
Describe the function of the constant region
The same in all antibodies.
Allows the antibody to bind to receptors on phagocytes.
Describe the function of the disulphide bridge
Holds the two heavy polypeptide chains together
Describe the functions of antibodies
Agglutination - Antibodies (agglutinins) can attach to 2 pathogens at the same time
Pathogens become clumped together
Phagocytes can engulf lots of pathogens at the same time
Neutralising toxins - Anti-toxins bind to specific toxins
Prevents the toxin affecting human cells
Prevent pathogens binding to human cells -
Antibodies bind to the pathogen
Blocks the receptor that the pathogen use to bind to host cells
Describe the process of clonal selection and clonal expansion in T lymphocytes
Each T lymphocyte has a different receptor on its surface
Each one is complimentary to a different antigen
The specific T lymphocyte binds to the antigen on the pathogen (clonal selection)
This activates the T lymphocyte
The T lymphocyte divides by mitosis to produce clones (clonal expansion)
State the different types of cells that T lymphocytes can differentiate into and describe their function
T helper cells - release interleukins to stimulate B lymphocytes
T killer cells - kill invaded body cells
T regulatory cells - suppress the immune system to stop the white blood cells attacking body cells
T memory cells - stay in the body, can differentiate quickly if the same pathogen enters the body again.
Describe the process of clonal selection and clonal expansion in B lymphocytes
Each B lymphocyte has antibodies on its surface
Each one is complementary to a different antigen
The antibody binds to the specific antigen on the pathogen (clonal selection)
The B lymphocyte also has receptors for interleukins
This activates the B lymphocyte
The B lymphocyte divides by mitosis to produce clones (clonal expansion)
State the different types of cells that B lymphocytes can differentiate into and describe their function
B plasma cells - produce antibodies
B memory cells - stay in the body, can differentiate quickly if the same pathogen enters the body again
For the primary response, describe when the pathogen enters, the speed of the response, the length of the response, the cells that are activated and if symptoms are shown
First time
Slower
Shorter
B & T Lymphocytes
Yes
For the secondary response, describe when the pathogen enters, the speed of the response, the length of the response, the cells that are activated and if symptoms are shown
Second time
Quicker
Longer
B & T memory cells
No
Explain why you don't show any symptoms the second time a pathogen enters the body
Memory cells recognise the pathogen
Clonal expansion and differentiation occur more quickly
The pathogens are destroyed before they can reproduce to produce large numbers
Describe the primary defences against pathogens in animals
Skin - A physical barrier to pathogens
Mucous membranes - Protect body openings by producing mucus to trap pathogens
Blood clotting - Plug wounds to prevent pathogen entry and blood loss
Expulsive reflexes - For example sneezing and coughing. Both attempt to expel foreign objects
Describe the process of phagocytosis
Cells at the site of a wound release cytokines to attract the phagocytes.
Phagocyte recognises the antigens on the pathogen.
An opsonin may be attached to the antigen to aid phagocytosis.
The phagocyte engulfs the pathogen.
The pathogen is contained in a phagosome.
A lysosome fuses with the phagosome and enzymes break down the pathogen.
The phagocyte presents the antigen to activate other cells in the immune system.
It is known as a APC (antigen presenting cell).
Name 4 types of cell you may see in a blood smear. For each one describe how you would be able to recognise it
Red blood cell - No nucleus
Monocyte (a type of phagocyte)- The biggest white blood cell, large, kidney bean shaped nucleus, non grainy cytoplasm
Neutrophil (a type of phagocyte) - Multi lobed nucleus, grainy cytoplasm
Lymphocyte - Much smaller than the phagocytes, the nucleus takes up most of the cell, little cytoplasm can be seen, but is not grainy
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