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Flashcards in Communicable diseases Deck (79)
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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



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

Blood clots and skin repair
Mucous membranes
Coughing and Sneezing


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?



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?



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
Guillain Barre


What type of molecule is an antibody?



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