Disease+Immunity Flashcards
What is disease
A condition that impairs the normal functioning of an organism
What is a pathogen
An organism that causes disease
What is a communicable disease
A disease that can spread between organisms
What does Tuberculosis affect and what pathogen is responsible for it
Animals, typically humans and cattle and is a bacterium
What does bacterial meningitis affect and what pathogen is responsible for it
Humans and bacterium
What does ring rot affect and what pathogen is responsible for it
Potatoes, tomatoes and is bacterium
What does HIV/AIDS affect and what pathogen is responsible for it
Humans and a virus
What does influenza affect and what pathogen is responsible for it
Animals including humans and is a virus
What does tobacco mosaic virus affect and what pathogen is responsible for it
Plants and virus
What does black sigatoka affect and what pathogen is responsible for it
Banana plants and a fungus
What does ringworm affect and what pathogen is responsible for it
Cattle and a fungus
What does athlete’s foot affect and what pathogen is responsible for it
Humans and a fungus
What does late blight affect and what pathogen is responsible for it
Potatoes/tomatoes and is a protoctist
What does malaria affect and what pathogen is responsible for it
Animals, including humans and a protoctist
What is direct transmission
When a disease is transmitted directly from one organism to another
What is indirect transmission
When a disease is transmitted from one organism to another via an intermediate such as air, water or food.
Examples of direct transmission
HIV through sexual intercourse or athlete’s foot via touch
Examples of indirect transmission
Late blight is spread when spores are carried between plants and malaria is spread between humans via mosquitoes as they act as vectors and spread it.
Three factors affecting disease transmission
Overcrowding, climate, social
Example of how overcrowding affects disease transmission
TB is increased risk with lots of people together in a small space as is spread by droplet infection which can remain in the air for long periods of time
Example of how climate affects disease transmission
- Late blight is common during wet summers as spores need water to spread
- Malaria is common in tropical countries as they are ideal conditions for mosquitoes
Example of how social factors affects disease transmission
- Good healthcare as people are less likely to be diagnosed and treated for HIV and drugs are less likely to be available and the disease more likely to be spread
- Good health education as helps to inform people how HIV is transmitted and how to avoid it
What are the primary non specific defense’s against pathogens in animals
Skin, mucous membranes, blood clotting, inflammation, wound repair, expulsive reflexes
How does skin act as a barrier to infection
Blocking pathogens from entering the body. Acts as a chemical barrier producing chemicals that are antimicrobial, can lower pH, inhibit the growth of pathogens
How does mucous membranes act as a barrier to infection
Protect body openings that are exposed to the environment, some secrete mucus a sticky substance trapping pathogens and contain antimicrobial enzymes
How does blood clotting act as a barrier to infection
It is a mesh of protein fibres that plug wounds to prevent pathogen entry and blood loss. They are formed by chemical reactions that take place when platelets are exposed to damaged blood vessels
How does inflammation act as a barrier to infection
It is triggered by tissue damage that releases molecules increasing the permeability of the blood vessels so they start to leak fluid into the surrounding area. This causes swelling and helps to isolate any pathogens that may have may have entered the damaged tissue. The molecule also causes vasodilation increasing blood flow to the affected area making it hot and brings WBC to infected area.
How does wound repair act as a barrier to infection
The skin is able to repair itself after injury preventing entry of the pathogen. The surface is repaired by the outer layer of skin cells dividing and migrating to the edges of the wound. The tissue below the wound then contracts to bring the edges closer using collagen fibres. Too many collagen fibres=scar.
How does expulsive reflexes act as a barrier to infection
Coughing and sneezing to expel foreign objects including pathogens using irritation.
What are the physical defenses against pathogens in plants
Waxy cuticle, cell walls and production of callose
How is the waxy cuticle used as a plant physical defenses
Produces a physical barrier against pathogen entry and also stops water collecting on the leaf reducing risk of infection
How is the cell walls used as a plant physical defenses
Form a physical barrier that are made past the waxy cuticle
How is the production of callose used as a plant physical defenses
It is a polysaccharide that gets deposited between plant cell walls and plasma membranes during times of stress (pathogen invasion). Callose deposition may make it harder for pathogens to enter cells and at the plasmodesmata limits the spread of viruses between cells.
What are the physical defenses against pathogens in animals
Produce antimicrobial chemicals and secrete toxic chemicals
How does the production of antimicrobial chemicals act as a chemical plant defence
They kill pathogens or inhibit their growth:
- Some plants produce saponins that destroy the cell membranes of fungi and other pathogens
- Some produce phytoalexins which inhibit the growth of fungi and other pathogens
How does the production of toxins act as a chemical plant defence
Reduces the amount of insect-feeding on plants and therefore reduces risk of infection by plant viruses carried by insects.
What are antigens
Molecules found on the surface of the cells that activates cells in the immune system as identifies the foreign body
What does the immune response involve
It involves specific (T and B lymphocytes) and non-specific stages
How does phagocytosis occur
1) A phagocyte recognizes the antigens on a pathogen
2) The cytoplasm of the phagocyte move round the pathogen, engulfing it. This may be made easier by the presence of opsonins
3) The pathogen in now contained in a phagosome
4) A lysosome fuses with the phagosome and the enzymes break down the pathogen
5) The phagocyte then presents the pathogen’s antigens. It sticks the antigens on its surface to activate other immune system cells. When a phagocyte does this is it acting as an antigen-presenting cell (APC)
What are opsonins
Molecules in the blood that attach to foreign antigens to aid phagocytosis. Some hide the negative charges on the membrane of the pathogen, making it easier for the negatively-charged phagocyte to get closer to the pathogen
What is a phagosome
A type of vesicle membrane that engulfs a pathogen
What are neutrophils
A type of phagocyte and the first WBC to respond to a pathogen as they move towards a wound in response to signals from cytokines.
What are cytokines
Proteins that act as messenger molecules and released by cells at the site of the wound.
What are the different types of T lymphocytes
(T) helper, killer and regulatory cells
What do T helper cells do
Release substance to activate B lymphocytes and T killer cells
What do T killer cells do
Attach to and kill cells that are infected with a virus
What do T regulatory cells
Suppress the immune response from other WBC to stop immune system cells from mistakenly attacking the host’s body cells.
T lymphocytes activate….
B lymphocytes, which divide into plasma cells
Phagocytes activate…
T lymphocytes
What are T lymphocytes
Type of WBC whose surface is covered with receptors which bind to antigens presented by APC’s. They each have a different lymphocyte on it’s surface
What is clonal selection
When a receptor on a T lymphocyte meets a complementary antigen it binds to it activating the T lymphocyte.
What are B lymphocytes
Type of white blood cell covered in antibodies that bind to antigens to form an antigen-antibody complex
What happens when an antibody on the surface of a B lymphocyte meets a complementary shaped antigen
It binds to it and along with substances from T helper cells it activates the B lymphocyte which is another form of clonal selection
What happens when an activated B lymphocyte divides
It will occur by mitosis into plasma and memory cells which is another form of clonal expansion
The process of cell signaling
A cell release a substance that binds to the receptors on another cell causing a response of some kind in the other cell
Why is cell signaling important
It helps to activate all the different types of WBC. For example, T helper cells interleukins that bind to receptors on B lymphocytes activating the B lymphocytes the T helper cells are signaling to the B lymphocytes that there’s a pathogen in the body
What do plasma cells make
More antibodies to a specific antigen
What are plasma cells
Clones of the B lymphocytes and secrete loads of the antibody specific to the antigen into the blood which bind to the antigens on the surface of the pathogen forming lots of antigen-antibody complexes
Structure of antibodies
Glycoproteins made from four polypeptide chains - two heavy and two light chains each with a variable region and a constant region
What do the variable regions do and how do their shape relate
Form the antigen binding sites and their shape is complementary to a particular antigen. The variable regions differ between antibodies
What does the hinge region do
Allow flexibility when the antibody binds to the antigen
What do the constant regions do
Allow binding to receptors on immune system cells such as phagocytes. It is the same in all antibodies
What are disulfide bridges
A type of bond that holds the polypeptide chains of the protein together
How do antibodies help to clear infection
Agglutinating pathogens, neutralizing toxins and preventing the
How does agglutinating pathogens help to clear infection
Each antibody has two binding sites so an antibody can bind to two pathogens at the same time leading to the pathogens becoming clumped together. Phagocytes then bind to the antibodies and phagocytose lots of pathogens all at once. This is known as agglutinins
How does neutralizing toxins help to clear infection
Toxins have different shapes and antibodies called anti-toxins can bind to the toxins produced by pathogens preventing the toxins from affecting human cells. The toxins are therefore neutralized and the toxin-antibody complexes are also phagocytosed.
How does preventing the pathogen binding to human cells help to clear infection
When antibodies bind to the antigens on pathogens, they may block the cell surface receptors that the pathogens need to bind to host cells. This means the pathogen can’t attach to or infect the host cells.
What happens when a pathogen enters the body for the first time
The antigens on its surface activate the immune system called the primary response.
Why is the primary response slow
There aren’t many B lymphocytes that can make the antibody needed to bind to it. Eventually the body will produce enough to overcome the infection however, meanwhile the infected person will show symptoms of the disease
What happens after being exposed to an antigen in the primary response
Both T and B lymphocytes produce memory cells which remain in the body for a long time
What do Memory T lymphocytes remember
Remember the specific antigen and will recognize a second time round
What do Memory B lymphocytes record
The specific antibodies needed to bind to the antigen
What happens during a secondary response
If the same pathogen reenters the system produce a quicker, stronger immune response. Clonal selection happens faster as Memory B lymphocytes are activated and divide into plasma cells that produce the right antibody to the antigen. Memory T lymphocytes are activated and divide into the correct type of T lymphocytes to kill the cell carrying the antigen. This happens before any symptoms show.
Difference table of primary and secondary response
Pathogen:
P = Enters for 1st time
S = Enters for 2nd time
Speed of response:
P = Slow
S = Fast
Cells activated:
P = B and T lymphocytes
S = Memory cells
Symptoms:
P = Yes
S = No
What is a blood smear
A sample of blood smeared over a microscope slide
What are you likely to see in a blood smear
RBC, WBC and platelets
How do you spot a RBC in a blood smear
They do not have a nucleus
How do you spot a neutrophil in a blood smear
Looks like three interconnected blobs and the nucleus is multi-lobed which grainy cytoplasm
How to spot a lymphocyte in a blood smear
It is small and the nucleus is very large
How to spot a monocyte in a blood smear
Biggest WBC and a type of phagocyte with a kidney bean shape nucleus and a non-grainy cytoplasm
What is active immunity
When your immune system makes its own antibodies after being stimulated by and antigen
What are the two types of active and passive immunity
Artificial and natural
What is active natural immunity
Become immune after catching a disease
What is active artificial immunity
When you become immune after you’ve been given a vaccination containing a harmless dose of antigen
What is passive immunity
Get from being given antibodies made by a different organism
What is passive natural immunity
When a baby becomes immune due to the antibodies it receives from its mother
What is passive artificial immunity
When you become immune after being injected with antibodies from someone else
Characteristics of active immunity
- Requires exposure to antigen
- Takes a while for protection to develop
- Protection is long-term
- Many cells are produced
Characteristics of passive immunity
- No exposure to antigen
- Protection is immediate
- Protection is short-term
- Memory cells aren’t produced
What happens when an organism’s immune system isn’t able to recognize self-antigens
The immune system treats the self-antigens as foreign antigens and launches an immune response against the organism’s own tissues.
Examples of autoimmune diseases
Lupus - caused by the immune system attacking cells in the connective tissues causing painful inflammation. It can affect the skin, joints and organs
Rheumatoid arthritis - caused by the immune system attacking cells in joints causing pain and inflammation
What is herd immunity
A large percentage of the population is vaccinated so there is not a likelihood of many catching it even if not everyone is vaccinated
What may the substances in vaccines be
Antigens - free or attached to a dead or attenuated pathogen
mRNA - designed to code for antigens triggering memory cells to be made
Define vaccination
The administration of a substance designed to stimulate the immune system
Define immunization
The process by which you develop immunity
What do routine vaccines include
MMR - measles, mumps and rubella given to children at 1 containing attenuated mmr viruses
Meningitis C - protects against bacteria that cause Meningitis C. Given at 3 months and boosters at 1 and teenagers
What are antibiotics
Chemicals that kill or inhibit the growth of bacteria (bacterial infections)
History of antibiotics
Penicillin became the first antibiotic by Alexander Fleming and they became widespread during the Second World War now meaning we have been able to deal with bacterial infections easier
Problem of antibiotic resistance
There is genetic variation in a population and therefore genetic mutations occur.
The antibiotic resistant bacteria MRSA
Meticillin-resistant staphylococcus aureus causes serious wound infections and is resistant to several antibiotics
The antibiotic resistant bacteria clostridium difficle
Infects digestive system causing problems in people who have already been treated with antibiotics. Thought that the harmless bacteria that are normally present in the digestive system are killed by the antibiotics
Why are doctors being encouraged to reduce their use of antibiotics
To reduce the risk of antibiotic resistance occuring
Why does biodiversity need to be protected in medicine
So that the drugs that are manufactured naturally can still be made such as penicillin from fungus
What are personalized medicines
Tailored to an individual’s DNA to precut how you will respond to different drugs and prescribe the most effective
/What is synthetic biology
Using technology to desgin and make artificial proteins, cells and microorganisms
