Communicable diseases Flashcards
What is a pathogen
An organism that lives by taking nutrition from a host and can cause harm in the process
What are the 4 main types of pathogen
Bacteria
Fungi
Viruses
Protoctista
How do bacteria reproduce
The divide via Binary Fission
How do bacteria cause damage
They divide so much they take up room and damage cells
Release waste products that are severly toxic to the host
How do Fungi cause damage in animals
Infections in the skin
The Hyphae grow under the skin to form a mycellium
Send out specialised reproductive hyphae to grow to the surface and release spores, often causing irritation
How do Fungi cause damage in plants
Live in vascular tissue
Hyphae release extracellular enzymes (Cellulase) which break down surrounding cells
Causes discolouration, wilting and death
How do Viruses reproduce
Take over the genetic machineary of a cell
Causing the cell to make copies of the virus
host cell bursts releasing the viruses into the body
How does a protoctist cause harm to a host
Enter a host cell
Feed off the cell as it grows
Reproduce inside cell
move to another cell once the one they were using is destroyed
name 3 examples of Bacteria
TB (Turburculosis): Affects the lungs
Bacterial Meningitis: Affects mengines (Membrane surrounding the brain and spinal chord)
Ring Rot: Decay of Vascular tissue (often potato or tomato)
name 3 examples of Fungi
Black Sigatoka: affects bannana leaves, reduces yeild
Ringworm: Growth of fungus in skin, can cause rash
Athletes Foot: Growth under skin of feet, cause skin decay
name 3 examples of Viruses
HIV/AIDS: Attacks immune system cells, compromises immune response
Influenza: Attacks respiritory system
Tobacco Mosaic Virus: causes discolouration of leaves
name 2 examples of Protoctista
Potato Blight: Affects leaves and potato tubers
Malaria: parasite in the blood, can cause coma and death
What are the 4 processes of Direct transmission
Physical contact: Toching an infected surface or person
Faecal-Oral transmission: Eating or drinking infected food or drink
Droplet transmission: Pathogen carried in water droplets in that air
Spore Transmission: Can be carried in air or on surfaces
What is Indirect transmissison
When the pathogens are transmited via a vector
How does indirect transmission occur in plants
As a result of insect attack, an insect like a beetle attacks an infected plant and then attacks a healthy plant after that
In what climate do most bacteria, fungi, and protoctista survive best in
A warm and Moist climate
What are passive defences
Defences that are present before infection, prevent entry and spread of the pathogen
Give 5 examples of Physical defences in Plants
Cellulose cell wall- prevents pathogens entering the cell
Lignin thickening of cell walls- lignin is waterproof and completely indigestible, prevents pathogen entry
Waxy Cuticles- prevent water collecting on cell surface, pathogens need water to survive
Bark- Contains many chemicals to kill pathogens
Stomatal Closure- Possible entry points for pathogens, when pathogen is detected the guard cells shut the stomata
What is Active defence
When pathogenic antigens are detected it starts a response by the organism
the organism fortifies defences that are already there
Give 4 examples of Active defences in plants
Cell walls become thicker by adding additional cellulose
Deposition of Callose between cell wall and cell membrane at infection site
Oxidative bursts- release highly reactive Oxygen molecules that can damage pathogens
Production of chemicals and toxins
What is necrosis and why does it occur
Necrosis is deliberate cell suicide
by killing cells around the infection the infection had no where to spread to and can thus contain the spread
What is canker?
A sunken necrotic lesion in woody tissue of a plant, causes death of cambium in the bark
What are primary defences against infection?
Defences that stop pathogens entering the body entirely
Give 5 examples of primary defences
Skin Blood clots and skin repair Mucous membranes Coughing and Sneezing Inflammation
Describe the skins role as a primary defence
Outer layer called epidermis
Cells called keratinocytes produced at the base of the epidermis
Move outward and their cytoplasm is replaced by keratin
Called keratinisation
The are dead when they are on the surface and provide a good shield to pathogens
What are clotting factors and why do we need them?
Molecules that when released cause an enzyme cascade that causes the blood to clot.
The prevent blood clots occurring in blood vessels where they are not needed
Why do we need mucous membranes and how do they act as a primary defence?
Exchange surfaces must be thinner to allow for exchange but are therefore less protected against pathogens
The mucous traps pathogens while allowing small molecules that need to be exchanged to pass through
What is the name of the cells that secrete mucous in the epithelium?
Goblet cells
How does the trachea and oesophagus prevent mucous building up in the airway?
Cilia waft the mucous to the top of the trachea where is enters the oesophagus where it is swallowed
How does coughing and sneezing act as a primary defence?
Areas that are prone to attack are sensitive
This means that when a pathogen enters it causes irritation and the body reflexes by coughing, sneezing or vomiting.
These expel pathogens before they have the chance to infect
How does inflammation act as a primary defence?
Presence of microorganisms is detected by mast cells
mast cells release histamine (cell signalling molecule)
Histamine has a range of effects
Including making the blood vessels more permeable to WBC’s and proteins.
This makes WBC’s and plasma leave the blood and enter tissue fluid.
Increases tissue fluid production causing oedema.
Fluid drained into lymphatic system which means pathogens removed by lymphocytes.
What is a secondary defence?
Combat pathogens that have already entered the body
What are antigens?
Molecules on the surface of pathogens that are recognised by the body.
What are opsonins?
A type of antibody that attaches to the antigens of pathogens
The are fairly non-specific so they can bind to a range of pathogenic cells
Their role is to enhance the effect of phagocytes
How do phagocytes destroy pathognes?
They engulf and digest the pathogens using digestive enzymes
What are the different types of phagocytes?
Neutrophils
Macrophages
How would you recognise a neutrophil?
Multi-lobed nucleus
How do neutrophils act to destroy pathogens?
They are released in large numbers at the time of an infection (short life)
They contain a large number of lysosomes that secrete digestive enzymes
The engulf and digest the pathogens and then die
The can build up as pus at an infection site when they die
How do macrophages act to destroy pathogens?
They settle in body tissues such as lymph nodes (long life)
When they engulf a pathogen they don’t fully digest it, instead they save the antigen from it and present it on their surface in a special protein complex
They become an antigen-presenting cell
The protein complex ensures that they aren’t mistaken for a pathogen
What is active immunity?
Where the body produces its own antibodies
What is passive immunity?
Antibodies are supplied from an external source
What is natural immunity?
When immunity is achieved by natural processes
What is artificial immunity?
When immunity is achieved via medical intervention
What is clonal expansion?
Making more and more of a particular type of cell
What type of cell division does clonal expansion use?
Mitosis
What are the 4 different types of T cells?
T helper
T killer
T memory
T regulator
What is the role of T memory cells?
provides the body with immunity if it is infected in the future
What is the role of T killer cells?
Directly kill viral infected cells
What is the role of T regulator cells?
Shut down immune respones
What is the role of T helper cells?
Release cytokines which stimulate clonal expansion of B cells
Stimulate more phagocytosis
Which cell undergoes clonal expansion first?
T cells
What are the 2 types of B cells?
Plasma Cells
B memory cells
What is the role of plasma cells?
Circulate in blood manufacturing and releasing antibodies
What is the role of B memory cells?
Remain in the body for a number of years allowing long lasting immunity
What cells does specific immune response involve?
B lymphocytes
T lymphocytes
How does an autoimmune disease occur?
Immune system attacks itself
Normally any T and B cells against our own antigens are destroyed
Can be caused by a problem with regulator cells
What are interleukins?
A type of cytokine that stimulates clonal expansion of T and B cells
Give examples of autoimmune diseases
Rhumatoid arthritis
Lupus
Guillain Barre
What type of molecule is an antibody?
Immunoglobulin
Describe the structure of an antibody
Y shaped made of 4 polypeptide chains
Variable regions can change shape depending on the antigen they are targeted to
Constant region is the same in all antibodies, may have a site for binding of phagocytes
Hinge region allows for flexibility so can bind to multiple antigens
What are the 3 ways an antibody can act?
Opsonins - Act as binding sites for phagocytes making phagocytosis more efficient
Agglutination - Each antibody has 2 binding regions so can bind to 2 pathogens. Bring pathogens closer together so phagocytes can engulf multiple at once
Anti-toxins - some antibodies bind to toxic molecules released by pathogens rendering them harmless
What is the primary immune response?
The immune response to an illness after the first time the host is infected by that pathogen
What is secondary immune respone?
The immune response to an illness the second time that the host is infected by that pathogen
What happens to the level of antibodies in the blood after an infection?
They drop rapidly
Compare and explain the concentration of antibodies in blood over time in the primary immune response and the secondary immune response
Primary response the levels take longer to reach the peak and the peak is a lot lower, this is because the body has to develop a new type of antibody for this antigen which takes a few days.
Secondary response levels rise a lot quicker and reach a much higher concentration. This is because the T and B memory cells are present from the primary immune response allowing the body to produce the antibodies a lot quicker
What type of immunity does a vaccine provide?
Artificial active immunity
artificial - done by medical intervention
active - the body creates its own antibodies
What are the different ways antigenic material can be put into a vaccine?
Attenuated (weakened) version of the pathogen
Dead pathogen
Preparation of the antigens from a pathogen
Toxoid (harmless version of a toxin)
What are two ways that vaccines control the spread of disease?
Herd Vaccination
Ring Vaccination
What is the principle of herd vaccination?
Immunising a vast majority of the people at risk of infection
The pathogen has no suitable hosts to spread to so doesn’t spread
You need to vaccinate about 90% of the population to be effective
What is the principle of ring vaccination?
Used when a new case of a disease is reported
Vaccinates all the people in the immediate vicinity of the new case
Mostly used to control spread of livestock disease by vaccinating all other animals at the farm and neighbouring farms
What is an epidemic?
A breakout of a disease that sees a rapid rise in number of infections in an area
Why are some pathogens more prone to epidemics than others?
Because they are more unstable so are more likely to undergo a genetic mutation
This mutation may change the shape of the surface antigen which renders T and B memory cells useless
Give an example of natural active immunity
When someone is infected with a disease like chickenpox they develop antibodies and can’t get it again
Give an example of natural passive immunity
A baby is provided with antibodies from the placenta and breast milk. They did not produce these but have gained them by natural processes
Give an example of artificial active immunity
When someone is vaccinated against a disease they produce their own antibodies but was caused by medical intervention
Give an example of artificial passive immunity
Immunity provided by the injection of antibodies made by another individual.
e.g hepatitis A and B vaccines
Why do we need to produce new medications?
New diseases are emerging (COVID-19)
We still don’t have effective treatments for a lot of diseases (e.g HIV)
Some antibiotics are becoming less effective (rise of resistant bacteria, e.g MRSA)
Give examples of modern medicines that developed from traditional medicines
Morphine - developed from traditional opium that was found in the sap of poppies. They reduce pain by reducing action in the peripheral nervous system
Aspirin and Ibuprofen - Developed from the active ingredient found in willow bark which was used historically as a pain killer
What is personalised medicine and how might it work?
Sequence genes from individuals with a certain condition and develop specific drugs for that condition
