4.1 - Commuicable Diseases Flashcards
Def of a pathogen
A microorganism that causes diseases
Different types of microorganism
Bacteria
Fungi
Virus
Protoctista
What do pathogens infect and why?
They live in the host
Host body creates a good habitat in which microorganisms can live
How do pathogens survive in the host?
They take nutrition form their host
But also cause damage in the process
Features of bacteria
Are prokaryotic cells
Can reproduce rapidly once in the host
Their presence can cause disease by damaging cells or by releasing waste products and/or toxins that are toxic to the host
In plants bacteria often live in vascular tissue and cause blackening and death of tissues
Fungi in animals
They live in the skin of an animal
It’s hyphae forms a mycelium underneaths the skin surface
Can send out specialised reproductive hyphae
These grow to surface of skin to release spores
This can cause redness and irritation
Fungi in plants
Often lives in vascular tissue of plants where it can gain nutrients
Hyphae release extracellular enzymes to digest surrounding tissue - causes decay
Leaves often become mottled in colour, curl up and shrivel, before dying.
Fruit and storage organs, like tubers in potatoes will turn black and decay
Features and effects of viruses
They invade cells and take over the genetic machinery and other organelles of the cell
They cause the cell to manufacture more copies of the virus
Host cell eventually burst, releasing many new viruses which infect healthy cells
Features and effects of protoctista
Enter host cell and feed on contents as they grow.
Malarial parasite “Plasmodium” has immature forms that feed on haemoglobin inside RBCs
Info about TB
Tuberculosis
Bacteria
Affects and kills may cells and tissues in the body, most often lungs
Info about bacterial meningitis
Bacteria
Infection of the meninges - membranes surrounding nerves and spinal cord
Causes damage to these areas
Info for ring rot
Bacteria
Affects plants
Causes ring of decay in vascular tissue of potato tuber or tomato, accompanied by leaf wilting
Info about HIV/AIDS
Virus
Attacks cells in the immune system and compromises the immune response
Info about influenza
Virus
Attacks respiratory systems and causes muscle pains and headaches
Tobacco mosaic virus info
Virus
Affects plants
Causes mottling and discolouration of leaves
Blight info(tomatoes and potatoes)
Protoctista
Affects plants
Affects both leaves and potato tubers
Ringworm(cattle)
Fungus
Growth of fungus in skin with spore cases erupting through skin to cause a rash
Athlete’s foot(humans)
Fungus
Growth under skin of feet - particularly between toes
Malaria info
Protoctistan
Parasite in blood that causes headaches and fever and may progress to coma and death
Def of direct transmission
Passing a pathogen form host to new host, with no intermediary
Def of indirect transmission
Passing a pathogen from host to new host, via a vector
Def of transmission
Passing a pathogen from an infected individual to an uninfected individual
Def of vector
An organism that carries a pathogen from one host to another
Short life cycle of a pathogen
Transmission from one host to another
Entering the host’s tissues
Reproducing
Leaving the host’s tissues
Different means of direct transmission
Direct physical contact - e.g touching
Faecal - oral transmission - eating contaminated food or water
Droplet infection - pathogen carried by tint water droplets in air
Transmission by spores -
How to prevent transmission by direct physical contact
Hygiene Keeping surfaces clean Cleaning and disinfecting cuts and abrasions Sterilising surgical equipment Using condoms during sex
How to prevent faecal-oral transmission
Treating waste and water
Thorough washing of all fresh food(using treated water)
Careful preparation and thorough cooking of all food(kill pathogens in food)
How to prevent transmission by droplet infection
Catch it - bin it - kill it
Cover mouth when sneezing
Ensure tissues are disposed of correctly after using
Preventing transmission by spores
Use of a mask
Washing skin after contact with soil
Social factors affecting transmission
Overcrowding in accommodation Poor ventilation in living space Poor health(especially HIV/AIDS) Poor diet Homelessness(bad hygiene) Living or working with people who have migrated from areas where disease is more common
What is an example of vectors in indirect transmission?
Mosquitoes in spreading malaria
Cycle of malaria transmission
A person with malaria contains gametes of “Plasmodium” in their blood Female anopheles mosquito sucks blood Plasmodium develops and migrates to mosquito’s salivary gland Uninfected person is bitten Plasmodium migrates to liver Plasmodium then migrates to blood Person then has malaria Cycle goes on
How can plants be affected by direct transmission?
Some pathogens present in soil and enter roots of the plant
Some fungi produce spores to reproduce, these can be carried in the wind
What do pathogens usually attack in a plant?
Vascular tissue
Can infect seeds so that offspring are infected
Indirect transmission into plants
Often occurs as a result of insect attack
Spores or bacteria attach to insect, e.g beetle
They act as vectors
Pathogen is transmitted to plant when insect attacks or eats it
E.g. Dutch Elm disease caused by Dutch elm beetle
What climates do pathogens thrive in most?
Most bacteria, fungi and protoctists reproduce more rapidly in warm and moist conditions
So are more common in these climates
So more infections in these areas
What happens to pathogens in cooler climates?
They can be damaged or even killed
Reduces their ability to grow and reproduce
Callose def
Large polysaccharide deposit that blocks old phloem sieve tubes
Why do plants need defences?
They don’t have an immune system
What are passive defences
Defences present before infection
Prevent entry and spread of pathogen
These include physical barriers and chemicals
Physical defences of a plant
Cellulose cell wall Lignin thickening of cell walls Waxy cuticle Bark Stomatal closure Callose Tulles Formation
Function of cellulose cell wall
Acts as a physical barrier
Contains variety of chemical defences activated once a pathogen is detected
Effect of lignin thickening of cell walls
Lignin is waterproof and completely indigestible
Effect of waxy cuticles
Prevent water collecting on cell surfaces
Since pathogens collect in water and need water to survive, the absence of water is a passive defence
Effect of bark in defence of plants
Contains a variety of chemicals that work against pathogenic organisms
Effect of stomatal closure
Stomata are possible points of entry for pathogens
Stomatal aperture is controlled by guard cells
When pathogens are detected, guard cells close stomata in that part of the plant
Effect of callose in plant defence
A large polysaccharide that is deposited in sieve tubes at end of growing season
Deposited around the sieve plates and blocks the flow of sieve tubes
Prevents a pathogen spreading around the plant
Tylose effect in plant
A balloon-like swelling/projection that fills the xylem vessel
When fully formed it plugs the vessel, so it cannot carry water.
Blocking xylem prevents spread of pathogens through heartwood
Tylose contains high concentration of chemicals, e.g terpenes are toxic to pathogens
Info about plant chemical defences
Plants contain chemicals that have variety of anti-pathogenic properties
Some are present before infection, e.g tannins in bark
Most chemical produced when pathogen is detected, as lots of energy required to make them.
Active defences in plants
Cell walls become thicker and strengthened with additional cellulose
Callose deposited between plant cell wall and cell membrane near invading pathogen - strengthens cell wall and blocks plasmodesmata
Oxidative bursts produce highly reactive oxygen molecules capable of damaging cells of invading organisms
Increase in chemical production
Necrosis - deliberate cell suicide. Sacrifice a few infected cells to save rest of plant
Different chemicals produced in plants
Terpenoids Phenols Alkaloids Defensive proteins(defensins) Hydrolytic enzymes
Description of terpenoids in plant
A range of essential oils that have antibacterial and anti fungal properties
May also have scent, e.g. menthols made by plants
Description of phenols in plant
Have antibiotic and anti fungal properties
Tannins found in bark inhibit attack by insects as bind to salivary proteins and digestive enzymes such as trypsin, deactivating the enzymes
Tannins can also cause of death of insects that ingest too much of it
Description of alkaloids in plants
Nitrogen-containing compounds such as caffeine, nicotine, cocaine, morphine.
Give bitter taste to inhibit herbivores feeding
Also act on a variety of metabolic reactions via inhibiting or activating enzyme action
Can also inhibit protein synthesis if ingested
Description of defensive proteins(defensins) in plants
Small cysteine-rich proteins that have broad anti-microbial activity.
Act upon molecules of the plasma membrane of pathogens
Possibly inhibit action of ion transport channels
Effect of hydrolytic enzymes in plants
Found in spaces between cells Include chitinases(break down chitin in fungal cell walls) Include lysosomes(capable of degrading bacterial cell walls
Def of inflammation
Swelling and redness of tissue caused by infection
Def of mucous membrane
Specialised epithelial tissue that is covered by mucus
Def of primary defences
Defences that prevent pathogens entering the body
Process of inflammation
Microbes detected by mast cells which release histamines
Histamines cause vasodilation - makes capillaries more permeable so more WBCs can leave
More tissue fluid forms as more plasma leaves
This causes swelling(odoema)
Tissue fluid can drain into the lymph vessels so pathogens may come into contact with lymphocytes (WBCs) and cause a specific immune response
Why we cough and sneeze
They are explosive reflexes
Irritation caused by microbes or their toxins causes expulsion which will carry microbes with it.
Process of blood clot
Blood vessel is damaged
Platelets bind to exposed collagen to form temporary plug
Platelets also release clothing factors which activate an enzyme cascade
Enzymes cause fibrinogen to form insoluble fibres which attach to the plug
Red blood cells are also trapped, this forms a clot
Process of skin repair after clot
Clot dries and forms a scab which pulls skin closer together
Under skin collagen is deposited
Stem cells in epidermis divide by mitosis and differentiate to form new skin cells at the edge of the cut
New blood vessels form
When edges of cut are drawn together the repair is complete
Other primary defences
Eyes are protected by antibodies and enzymes in the tear fluid
Ear canal is lined by ear wax, which traps pathogens
Female reproductive system protected by a mucus plug in the cervix and by maintaining relatively acidic conditions in the vagina
Def of antigen-presenting cell
A cell that isolates the antigen from a pathogen an places it on the plasma membrane so that it can be recognised by other cells in the immune system
Def of clonal selection
Selection of specific B or T cell that is specific to the antigen
Def of cytokines
Hormone-like molecules used in cell signalling to stimulate the immune response
Def of neutrophil
A type of WBC that engulfs foreign matter and traps it in a large vacuole(pagosome), which fuses with lysosomes to digest the foreign matter
Def of opsonins
Proteins that bind to the antigen on a pathogen and allow phagocytes to bind
What are secondary defences used to combat?
Combat pathogens that have entered the body
What do opsonins do?
Enhance the ability of phagocytise cells to bind and engulf the pathogen
3 types of phagocytes
Neutrophils
Macrophages
Antigen-presenting cells
2 types of lymphocytes
B cells
T cells
What is clonal selection?
Activation of the specific B and T cells
This leads to the production of antibodies that can combat the specific pathogen
Also leads to production of memory cells that provide long-term immunity
Def of antibodies
Specific proteins released by plasma cells that can attach to pathogenic antigens
Def of B memory cells
Cells that remain in the blood for a long time, providing long-term immunity
Def of clonal expansion
An increase in the number of cells by mitotic cell division
Def of interleukins
Signalling molecules that are used to communicate between different white blood cells
Def of plasma cells
Derived from B lymphocytes, these are cells that manufacture antibodies
Def of T helper cells
Cells that release signalling molecules to stimulate the immune response
T killer cells def
Cells that attack and destroy our own body cells that are infected by a pathogen
Def of T memory cells
Cells that remain in the blood for a long time, providing long-term immunity
Def of T regulator cells
Cells that are involved with inhibiting or ending the immune response
Four types of T lymphocytes
T helper cells
T killer cells
T memory cells
T regulator cells
Function of t helper cells
Release cytokines that stimulate the B cells to develop and stimulate phagocytosis by the phagocytes
Function of T killer cells
They attack and kill host-body cells that display the foreign antigen
Function of T memory cells
These provide long term immunity
Function of T regulator cells
These shit down immune response after pathogen has been successfully removed.
Also involved in preventing autoimmunity
2 types of B lymphocytes
Plasma cells
B memory cells
Function of plasma cells
Type of B lymphocyte
Circulate in the blood, manufacturing and releasing antibodies
Function of B memory cells
Remain in body for a number of years and act as immunological memory
Examples of communication using cytokines
- Macrophages release monokines
Some of these attract neutrophils(by chemotaxis)and others stimulate B cells to differentiate and release antibodies - T cells and macrophages release interleukins, which can stimulate clonal expansion(proliferation) and differentiation of B and T cells
- Many cells can release interferon, which inhibits virus replication and stimulates activity of T killer cells
What are autoimmune diseases?
Occurs when immune system attacks a part of the body.
Arises when antibodies start to attack our own antigens - possibly because antigens that are not normally exposed become exposed to attack
Process of phagocytosis
- Receptor on phagocyte’s cell surface membrane binds to antigen on pathogen’s cell surface membrane
- Pathogen engulfed by endocytosis
- This produces a phagosome
- Lysosomes fuse with phagosome, releasing enzymes(lysins) into it
- The pathogen is digested into amino acids and fatty acids
- Products are absorbed into cytoplasm by diffusion
- Phagocyte can incorporate antigens into cell membrane to become an antigen-presenting cell
Where are each lymphocyte produced and found?
B lymphocytes - mature in the bone marrow
T lymphocytes - mature in thymus
Both cells have large nuclei and specialised receptors on their cells surface membranes
Mature B and T lymphocytes circulate around blood and lymph
Three ways to trigger an immune response
Pathogen detected in blood stream
Antigens presenting cells
Antigens on infected host cells detected
Process of triggering an immune response
- Antigens on pathogen’s surface communicate to body cells is foreign
- To initiate immune response, pathogens have to be detected by B and T lymphocytes with complementary receptors on pathogen’s antigens
- Infected cells sometimes get pathogen’s antigens on their surface - helps to select right B and T lymphocytes
- Macrophages in the lymph nodes engulf and digest pathogens. They separate the pathogen’s antigens and incorporate them into their own cell surface membrane. They are now antigen presenting cells ‐ they increase the chances of the correct T lymphocytes locating the foreign antigens.
• The selection of the correct lymphocytes with receptors complementary in shape to the antigens is call clonal selection.
• More of these lymphocytes are needed to fight the pathogens so they divide by mitosis in clonal expansion.
Another name for immune response
Humoral immunity
Examples of cell signalling in immune response
- Pathogen’s antigens communicate to body cells that they are foreign
- Cells infected with foreign antigens on surface communicate to lymphocytes to be selected in clonal selection and to T killer cells that they need to be killed
- Macrophages engulf and digest pathogens and incorporate pathogen’s antigens on their cell surface membrane
This communicates to lymphocytes to be selected in clonal selection - T helper cells release cytokines
These bind to receptors on B cells and stimulate them to divide by mitosis and differentiate
Primary Immune Response info
- there is a time delay to trigger immune response after first infection
- takes time for clonal selection and clonal expansion to happen
- no memory cells ‐ slow antibody production and few produced
Secondary Immune Response Info
- T memory cells & B memory cells are already present in the blood ‐ antibody production is immediate (clonal selection and clonal expansion happen faster)
- higher level of antibody production and antibodies produced more quickly
Diff between secondary and primary immune response
Secondary:
Produces antibodies immediately after exposure
Produces more antibodies
Antibodies produced more quickly
What are autoimmune diseases?
When the immune system attacks the body
Occurs when antibodies start to attack our own antigens
Examples of autoimmune diseases
Arthritis - antibodies attack the membranes around joints
Lupus - antibodies attack proteins in the nucleus
Why we need to find new drugs
New drugs needed to combat new diseases
New antibiotics needed as some strains of bacteria have evolved antibiotic resistance
How are new drugs found?
- Produced naturally by microbes
E.g. penicillin - Some plants produce compounds with medicinal properties
Isolate active ingredients on plant medicines - Maintain Biodiversity
To find new sources of drugs
What is personalised medicine?
Where the genomes of plants or microorganisms are screened to identify medicinal compounds
Idea is that scientists will eventually be able to sequence genes from individuals and develop specific drugs for the condition
What is synthetic biology?
The development of new molecules that mimic biological molecules
E.g. enzymes
Use of antibiotics
Used to treat/avoid bacterial infection
Benefits of antibiotics
Prevent infection after surgery - reduces complications/death rate
Treat infections that the body can’t ‘fight off’
Risks of antibiotics
Overuse and misuse of antibiotics allow bacterial strains to become resistant to antibiotics
- antibiotic resistance
This means certain antibiotics will be less effective/won’t have an effect of the bacteria
Why is the term ‘immune’ incorrect when referring to bacteria and antibiotics?
- Because the term is “resistant”
Immune implies they have an immune system
They don’t as they are single called organisms
Def of active immunity
Where the immune system is activated and manufactures its own antibodies
Def of artificial immunity
Immunity achieved as a result of medical intervention
Def of epidemic
A rapid spread of diseases through a high proportion of the population(national)
Def of vaccination
A way of stimulating an immune response so that immunity is achieved
Def of natural immunity
Immunity achieved through normal life processes
Def of passive immunity
Immunity achieved when antibodies are passed to the individual through breast feeding or injection
What in the blood provides immunity to a disease
The memory lymphocytes
What is antigenic material
A source of antigens
Different sources of antigens
Whole, live microorganism
A harmless or weakened version of the pathogen
A dead pathogen
A preparation of the antigens from a pathogen
A toxoid, a harmless version of a toxin
Two applications of vaccinations
Herd Immunity
Ring Vaccination
Description of herd immunity
Vaccinate all people that are at risk from the disease
Vaccinate enough of the population(85-95%) and it stops the infection spreading, as there won’t be enough people to infect
Description of ring vaccination
Vaccinate all people with or near victim
Contain the spread of disease within ring/certain area
Requires people to report victims of disease or infected
How to identify Neutrophils
They have a multi-lobed nucleus
Facts about neutrophils
Have a multi-lobed nucleus
Manufactured in bone marrow
Travel in blood - often squeeze out of blood trough capillaries into tissue fluid
Released in large numbers on response to infection
Macrophages facts
H
Antigen presentation
Antigen presenting cells move around body where can come into contact with specific cells and activate the immune response
These are B and T lymphocytes
The antigen-presenting cells increase chances that the lymphocytes will come into contact with pathogen
What is clonal expansion?
When the chosen lymphocytes divide by mitosis and differentiate
