C12 - Communicable diseases Flashcards
What is a communicable disease
Diseases that can be passed from one organism to another
What is a pathogen
Microorganisms that cause disease
What is a vector
Living/non-living organism that transmits a pathogen from one organism to another
What is bacteria
Prokaryote - no membrane bound nucleus or organelles
Only small proportion are pathogens
How can bacteria be classified
-By shapes
-By cell walls
What is a virus
Non-living infectious agent
Genetic material (DNA/RNA) surrounded by protein
All are pathogenic
What is a bacteriophage
Viruses that attack bacteria
What are protoctista/protista
Eukaryotes with wide range of feeding methods
Small amount are pathogens (parasites)
Require hosts
What are fungi
Eukaryotes
Cannot photosynthesise
So digest food extracellularly
Some fungi are parasites so pathogens
Spores enable rapid reproduction
How do viruses damage host tissues directly
Viral genetic material inserted into host DNA
Host cell makes more viruses
Viruses burst cell, destroying it. then infecting more cells
How do protoctista damage host tissues directly
Digest and use cell contents as they reproduce
How do fungi damage host tissues directly
Digest living cells destroying them
What type of pathogens release toxins
Bacteria
Fungi
What is a bacterial disease that affects plants
Ring rot
Damages leaves, tubers and fruit
No cure, once infected field cannot be used
What is a viral disease that affects plants
Tobacco mosaic virus
Damages leaves, flowers and fruit
Stunts growth, reduces yield
No cure, resistant crop strains available
What is a protoctista disease that affects plants
Potato blight
Destroy leaves tubers and fruit
No cure
Resistant strains, management, chemical treatments
What is a fungal disease that affects plants
Black sigatoka
Destroys leaves, turning them black
Reduces crop yield
No cure
Fungicide
What is a bacterial disease that affects humans
Tuberculosis
Damages and destroys lung tissue, suppresses immune system
Curable by antibiotics
Preventable by vaccination
What is a viral disease that affects humans
HIV/AIDS
Targets T helper cells, destroys immune system
Spread through unprotected sex, shared needles, from mothers to babies
No cure
Antiretroviral drugs help
What is a viral disease that affects humans (2)
Influenza
Infects ciliated epithelial cells, killing them, vulnerable to infection
No cure
Vaccines
What is a protoctista disease that affects humans
Malaria
Vector is mosquitos, spread through bite
Invades rbc, liver, brain
No vaccine, limited cures
Mosquitos destroyed by insecticides
What is a fungal disease that affects humans
Athlete’s foot
Grows on and digests warm, moist skin
Causes cracking, scaling which is itchy
Cure is antifungal cream
How can pathogens be transferred between animals directly
-Direct contact (touch)
-Inoculation (break skin)
-Ingestion (mouth)
How can pathogens be transferred between animals indirectly
-Fomites (inanimate object)
-Droplet infection (inhalation)
-Vectors
-Water (vector for disease)
Factors affecting transmission of communicable disease in animals
-Overcrowding
-Poor nutrition
-Compromised immune system
-Poor waste disposal
-Climate change
-Culture and infrastructure
-Socioeconomic factors
Direct transmission of pathogens between plants
Contact of healthy plant with any part of a diseased plant
Indirect transmission of pathogens between plants
-Soil contamination (spores left in soil)
-Vectors (wind, water, animals, humans)
Factors affecting transmission of communicable disease in plants
-Planting variety of crops susceptible to disease
-Overcrowding
-Poor mineral nutrition
-Damp, warm conditions
-Climate change
How do plants recognise and respond to an attack
Receptors respond to molecules from pathogen or to chemicals produced when cell wall attacked
Stimulates release of signalling molecules which switch on genes in nucleus
Triggers cellular responses
What is callose
Polysaccharide containing beta 1-3 linkages and beta 1-6 linkages between the glucose monomers
High levels produced during immune response
What are plants physical defences
-Callose synthesised, deposited between cell wall and membrane next to infected cells, barriers preventing pathogens entering
-Lignin added to make barrier thicker and stronger
-Callose block sieve plates preventing spread
-Callose deposited in plasmodesmata preventing spread
What are plants chemical defences
-Insect repellents
-Insecticides
-Antibacterial compounds
-Antifungal compounds
-Anti-oomycetes
-General toxins
How does blood clot
When platelets come into contact with collage/wall of damaged blood vessel, they adhere and secrete substances
-Thromboplastin: enzyme that triggers cascade of reactions forming blood clot
-Serotonin: makes smooth muscle in walls of blood vessel contract, reducing blood supply
Clot dries forming scab keeping pathogens out
Damage blood vessels regrow
Once epidermis reaches normal thickness scab goes
What are non-specific animal defences
-Skin acts as a physical barrier, sebum inhibits growth of pathogens
-Many body tracts lined with mucous membranes containing lysozymes , trapping and destroying pathogens
-Lysozymes in tears and urine/acid in stomach
What is the inflammatory response
Localised response to pathogens resulting in inflammation
Mast cells are activated in damaged tissue and release chemicals called histamine and cytokines
-Histamines dilate blood vessels causing localised heat and redness (raised temp prevents pathogens reproducing)
-Histamines make blood walls more leaky so tissue fluid forced out causing swelling and pain
-Cytokines attract phagocytes
What are non-specific immune responses
Fevers
Phagocytosis
How do fevers protect the body
Body temp is 37C
-Higher than most pathogens optimum temperature
-Temp inc during immune response, immune response works faster at high temp
What is phagocytosis
Process by which wbc called phagocytes recognise non-self cells, engulf them, digest them within a vesicle (phagolysosome)
Describe phagocytosis
1) Pathogen produces chemicals that attract phagocytes
2) Phagocytes recognise non-human proteins on pathogen
3) Phagocyte engulfs pathigen enclosing it in a vacuole called a phagosome
4) Phagosome combines with ly some forming phagolysome
5) enzymes from lysine digest and destroy pathogen
What are two types of phagocytes
Neutrophils
Macrophages
How do macrophages engulf and destroy a pathogen
1) Digest pathogen
2) Combines antigen from pathogen with special glycoproteins in the cytoplasm (major histocompatibility complect)
3) MHC moves pathogens antigens to macrophages surface membrane creating antigen presenting cell (APC)
4) Antigens stimulate other cells involved in specific immune response
How can you identify a specific or non specific response from blood smear
Identifying type of lymphocyte
What are cytokines
Produced by mast cells
Cell-signalling molecules that attract phagocytes to site of infection
Increase body temp, stimulate immune response
What is an opsonin
Chemicals that bind to pathogens and tag them so they are recignised by phagocytes more easily
What is an opsonin
Chemicals that bind to pathogens and tag them so they are recignised by phagocytes more easily
What is an antigen
Identifying chemical on the surface of a cell that triggers an immune response
What is an antibody
Y shaped glycoprotein made by B cells of the immune system in response to the presence of an antigen.
Bind to a specific antigen on a pathogen or toxin that has triggered an immune response
What is the structure of an antibody
4 chains: 2 heavy polypeptide chains, 2 shorter light polypeptide chains
Chains held together by disulphide bridges
Variable region is different (specificity)
Hinge region provides flexibility so it can bind to two antigens
Constant region is same on all antibodies
What is the specific immunity
Immune system remembers antigen after initial response, leading to enhanced response to subsequent encounters
(aka active/acquired immunity)
What is an antigen-antibody complex
Complex formed when an antigen binds to an antibody
What are immunoglobulins
Y-shaped glycoproteins that form antibodies
How do antibodies defend the body
-Act as agglutinins causing pathogen carrying anybody-antigen complexes to clump together, prevents spread, easier for phagocytes to engulf
-Acts as anti-toxin, binding to toxins produced by pathogen making them harmless
-Acts as opsonin so complex easily engulfed and digested by phagocyte
-Pathogens can no longer invade host cells when part of complex
Where do T lymphocytes mature
Thymus gland
Where do B lymphocytes mature
Bone marrow
What are the main types of T lymphocytes
T helper cells
T killer cells
T memory cells
T regulator cells
What are the main types of B lymphocytes
Plasma cells
B effector cells
B memory cells
What is a T helper cell
Contain CD4 receptors on cell-surface membranes which bind to antigens on APCs
produce interleukins (cytokinesis- cell signalling molecule) stimulating activity of B cells
This inc antibody production , stimulates production of other T cells, attracts macrophages
What is a T killer cell
Destroy pathogen carrying antigen using perforin which makes holes in cell membrane
What is a T memory cell
Live for long time
Part of immunological memory
Divide rapidly into clones of T killer cells if subsequent exposure to antigen
What is a T regulator cell
Suppress immune system to control and regulate it
Stop immune response once pathogen is eliminated
(Req interleukins)
What is a plasma cell
Produce and release antibodies for specific antigen
Live for few days
What is a B effector cell
Divide to form plasma cell clones
What is a B memory cell
Live for long time
Provide immunological memory of specific antigen
Make subsequent responses rapid
What is cell mediated immunity
Response to cells which have been changed
1) Macrophages engulf and digest pathogens in phagocytosis, form APCs
2) Receptors on some T helper cells fit antigens so become activated and produced interleukins which stimulate more T cells to divide by mitosis
3) Cloned T cells may:
-Devp into T memory cells
-Produce interleukins stimulating phagocytosis/B cells to divide
-Stimulate devp of T killer cells specific to antigen
What is humoral immunity
Response to antigens found outside cells and APCs
B lymphocytes have antibodies on their cell surface membrane
1) Activated T helper cells bind to B cell APC (clonal selection - B cell with correct antibody selected)
2) Interleukins secreted by T helper cell to activate B cell
3) Activated B cell divides by mitosis to give clones of plasma cells and B memory cells (clonal expansion)
4) Cloned plasma cells produce complimentary antibodies that disable antigens or act as opsonin/agglutitins (Primary immune response)
5) Some cloned B cells become B memory cells (Secomdary immune response)
What is an autoimmune resonse
Immune system acts against its own cells and destroys healthy tissue in the body
What is natural active immunity
Immunity which results from the response of a body to the invasion of a pathogen
What is natural passive immunity
Immunity given to an infant by the mother through the placenta and colostrum
What is artificial active immunity
Immunity which results from exposure to a safe form of a pathogen
Artificial passive immunity
Immunity which results from the administration of antibodies from another animal against a pathogen
How does a vaccine work
1) Pathogen made safe so antigen is intact but no risk of infection (killed/inactivated, weakened, altered, detoxified,isolated, gm)
2) Small amounts injected into blood
3) Primary immune response triggered so body produces memory cells
4) Secondary immune response triggered in subsequent exposure to pathogen
What is an epidemic
When communicable disease spreads rapidly to a lot of people on a local or national level
What is a pandemic
When a communicable disease spreads to a lot of people across a number of countries
What is herd immunity
Significant number of people have been vaccinated so it gives protection to people who haven’t been
What is penicillin
First widely used safe antibiotic derived from mould Penicillium notatum
Who discovered penicillin and how
Alexander Fleming in 1928
Found mould Penicillium chrysogenum growing on Staphylococcus cultures
How are many medicines manufactured now
Chemical processes
Some still extracted from organic biological compounds
Penicillin- commercial extraction og from mould growing on melons
What’s pharmocogenomics
Science of interweaving knowledge of drug actions with personal genetic materials
-Personalised medicine
What is synthetic biology
Using genetic engineering techniques, bacteria can be developed that produces drugs needed
What is selective toxicity
Ability to interfere with the metabolism of a pathogen without affecting the cells of the host
What is the antibiotic dilemma
Antibiotic resistance
What is antibiotic resistance
Antibiotics work because bacterium has binding site for drug
During reproduction, mutation can occur making antibiotic ineffective
Natural selection will cause large population of antibiotic resistant bacteria
Overuse of antibiotics can encourage this
Give 2 examples of antibiotic resistant bacteria
MRSA (methicillin resistant Staphylococcus aures)
-Causes boils and abcesses
Clostridium difficile
-Produces toxins that damage gut
How can antibiotic resistance be reduced
-Minimising use of antibiotics
-Good hygiene in hospitals
