12 - Communicable Diseases Flashcards
Define communicable disease
A disease, caused by a pathogen, that can be passed from one organism to another
What are bacteria cell walls made from
peptidoglycan
How to bacteria replicate
Binary fission
How are types of bacteria classified
Shape
Structure of cell walls (gram + or gram -)
Describe how different types of bacteria may appear different on staining
Gram-positive - walls are thicker - blue/purple colour
Gram-negative - appear red
How do bacteria make us feel ill
Production of toxins
How do viruses replicate?
Take over body cells and use their, mechanisms to replicate genetic material, cells are burst - releasing new viral particles
Describe the structure of a virus (4)
Genetic material (DNA or RNA)
surrounded by a protein coat (capsid)
surrounded by an envelope (phospholipid bilayer)
containing glycoproteins
Draw the structure of a virus
Revision number 4
Describe the life cycle of a virus (6)
attachment to cell penetration of cell uncoating gene replication and expression assembly release
Viruses that attack bacteria are called
bacteriophages
Why are the labels gram-positive and gram-negative useful?
The structure of the cell walls determine how they react to antibiotics so this information can inform the production of antibiotics
What is the cell wall of fungi made of?
Chitin
Describe the structure of protoctists and how they spread
eukaryotic
parasitic (use people or animals as host)
may need a vector to transfer or through polluted water
Describe the structure of fungi and how they spread
eukaryotic (multicellular or unicellular)
absorb food broken down by extracellular enzymes
parasitic
release spores to reproduce
Name the 4 plant diseases we study and what type of pathogen they are
Tobacco mosaic virus - virus
black Sigatoka - fungus
ring rot - bacterial
blight - protoctist
Name 5 reasons reducing infections in plants is important
- yield of crops
- quality of crop
- waste food
- food security
- extinctions
- habitats and biodiversity
What are the 2 ways plants can spread disease
Direct contact - eg. leaves touching leaves
Indirect contact - transported via vector eg. wind, water, animals, insects, contaminated soil
describe how ring rot affects plants and any cures or preventions
bacterial infection
leaves, tubers and fruit damaged
no cure - field can not be used for 2 years
describe how tmv affects plants and any cures or preventions
viral infection
leaves damaged, reduces yield and stunts growth
no cure - resistant crop strains available
describe how blight affects plants and any cures or preventions
protoctist
destroys leaves, tubers and fruit
no cure - resistant crop strains available, management and chemical treatments can reduce infection risk
describe how black sigatoka affects plants and any cures or preventions
fungal infection
destroys leaves (turn black), reduction in yield
fungicides can control spread
describe 4 factors that affect the transmission fo plant disease
monocultures
- diseases spread quickly
climate change
- more rain and higher temp. lead to higher transmission
poor farming practice
- same species in soil every year and not disinfecting tools increases indirect spread
overcrowding
- closer means more direct contact
-poor ventilation means greater humiidy, promotes growth of pathogens
State 5 ways to reduce the spread of plant dieases
leave space between plants remove all traces of plants after harvesting general hygiene eg. sterilising tools pest control eg. pesticides removing and burning infected plants annual crop rotation
State the 7 animal diseases we study
TB Bacterial meningitis HIV/AIDs Influenza Malaria Ring Worm Athletes foot
Describe TB affects animals and any cures or preventions
bacterial infection
damages/destroys lung tissue and suppresses immune system
curable by antibiotics
preventable by vaccination and improving living standards
Describe Bacterial meningitis affects animals and any cures or preventions
bacterial infection
infection of meninges in brain, can spread to body and cause blood poisoning
blotchy rash (does not disappear when a glass is pressed to it)
curable by antibiotics
vaccinations prevent some forms
Describe HIV/AIDS affects animals and any cures or preventions
viral infection
gradual destroys immune system
transmitted through bodily fluids
no vaccination and no cure but antiretroviral drugs can slow transmission in body
Describe Influenza affects animals and any cures or preventions
Viral infection
infection of ciliated epithelial cells in gaseous exchange system
no cure, mutates regularly, vaccination immunity only lasts for a few years max
Describe malaria affects animals and any cures or preventions
protoctist
spread through bites of infected mosquitoes
makes you weak and vulnerable to other infections
no cure and limited treatment - per cent by controlling vector eg. nets, long sleeves removing still water breeding ground
Describe Ring worm affects animals and any cures or preventions
fungal infection
grey-white crusty, infectious, circular areas of skin
antifungal creams effective cure
Describe athletes foot affects animals and any cures or preventions
fungal infection
grows on and digests warm, moist skin between toes
antifungal creams effective cure
State at least 5 factors that affect the transmission of animal diseases
overcrowded living conditions
lack of clean running water and sanitation
compromised immune system
poor nutrition
lack of vaccinations
lack of trained doctors
poor infrastructure eg. no access to health care
What are the 2 catagories for plant defences?
physical and chemical
Name at least 5 physical plant defences
- wavy cuticle on leaves
- callose production
- lignified xylem
- stomatal closure
- meristems
- plants can seal off and lose infected “limbs”
How do pathogens get into plants
physcial wounds eg. storm damage, cuts, animals biting off bark etc.
insect vectors eg. aphids
give an example fo an active defence mechanism for plants
callose production
what is callose
polysaccharide, polymer of b- glucose
how does callose production protect a plant from infection
callose is synthesised and deposited in
-sieve plates - prevent pathogen from spreading further
plasmodesmata - prevent pathogen from spreading between cells
-between cell walla and membrane - sealing cell off to prevent spread
When do cells produce callose?
When they detect an infection, either detect chemicals released by pathogens (eg. toxins) or products of cell wall hydrolysis (which is catalyzed by enzymes released by pathogens)
What are the 4 stages in the non-specific immune response in plants?
RSGD Recognise Signaling Gene Expression Defend
In the non-specific immune response in plants, what does signaling mean?
Cell signaling- molecules active the defense genes
In the non-specific immune response in plants, what does gene expression mean?
defensive chemicals made (proteins) or enzymes to make the chemicals are made in the ribosomes
In the non-specific immune response in plants, what does defend mean?
directly attack pathogen/ communicate with other cells/ cause cell death
What is necrosis?
cell suicide, cells are sacrificed to prevent the spread of a pathogen
Name at least 5 chemical defenses in plants
- insect repellents
- insecticides
- antibacterial compounds
- antifungal compunds
- anti-oomycetes
- general toxins
Name at least 5 ways of limiting the spread of disease in humans
Antibiotics Vaccinations Isolating infected individuals avoiding contact washing hands covering mouth when coughing or sneezing condoms good food hygiene reducing overcrowding clean water and good sanitation
Name at least 5 non-specific barriers against pathogens in animals
skin mucous membranes lysozymes (in tears and urine) saliva gut bacteria
How does skin act as a barrier against pathogens
physical barrier, bacteria on skin outcompete pathogens
sebum acts a an antimicrobial compund
How do mucous membranes act as a barrier against pathogens
traps microbes, contains phagocytes and lysozymes
How do cilia act as a non-specific defense against pathogens
surface of gaseous exchange system
sweep mucus out of airways and to the back of the throat where it is swallowed and destroyed by stomach acid
Name 4 expulsive réflexes and how the defend against infection
Coughing Sneezing Vomiting Diarrhoea Physically expels pathogens from body
What component of the blood causes blood clots and where are these made
Platelets/thrombocytes
Fragments of cells made in the bone marrow
What are the 4 steps involved in blood clotting?
1 - platelets come into contact with collagen (skin/outside do blood vessels) and are activated
2 - platelets adhere to surface of damaged area and stick to each other
3 - produce serotonin - blood vessels contract
4 - produce thromboplastin enzyme - triggers reactions leading to blood clot
How does a blood clot prevent infection from pathogens?
Clots dries to form a tough hard scab to keep pathogens out - physical barrier
Epidermal cells grow beneath scab, wound is healed
What type of immune response is an inflammatory response
Non-specific localised response
What are the symptoms of inflammatory response?
Pain
Heat
Swelling
Redness
What starts an inflammatory responses?
Mast cells, type of WBC, activated
Release histamines and cytokines
What 2 chemicals are released in inflammatory response?
Histamines and cytokines
What do histamines do?
Cause blood vessels to dilate - increase blood supply = more WBCs, Increases temperature - unfavourable for pathogens
Increases permeability of capillaries - blood plasma forced out, causes swelling
What do cytokines do?
Attract phagocytes to are to destroy pathogens by phagocytosis
- stimulate specific immune response
- stimulate hypothalamus to increase temp - unfavourable conditions for pathogen
Why do your lymph nodes swell due to an inflammatory response
Lymphatic fluid joins back circulation at lymph nodes, more WBCs needed there to filter fluid and destroy pathogens causing swelling
What are antigens
Glycolipids of the surface of cells
What type of things can be (/have) antigens?
Allergens
Abnormal cells eg. Cancer cells
Non-self cells eg. Transplanted organ or blood transfusions
Pathogens
What is phagocytosis?
The process by which pathogens are engulfed and destroyed (hydrolysed)
What are the 2 types on WBCs in phagocytosis?
Neutrophils and macrophages
What is the difference between neutrophils and macrophages
Neutrophils are quick responders
Macrophages are more slow and become antigen presenting cells
What are the 5 stages on phagocytosis
Recognition Attachment Engulfing Digestion Antigen Presentation
When a pathogen is engulfed where does it go and how is it digested?
Vesicle-like structures called phagosomes, these are fused with a lysosomes containing hydrolytic enzymes that hydrolyse the pathogen
After a pathogen is digested in phagocytosis, what happens to the debris?
Soluble debris is ejected through exocytosis
Antigens are combined with major histocompatibility complex and presented on surface
What cells control our specific immune response?
WBCs- T lymphocytes and B lymphocytes
What type of immune response do T lymphocytes control?
cell mediated immunity
What type of immune response do B lymphocytes control?
humoral response
What is cell-mediated immunity?
response to self cells that have been changed in some way eg. infection with a virus, cancerous, APCs
What is humoral immunity?
Response to antigens found detached (from non-self cells or APCs)
Describe the stages of cell-mediated immunity (up to differentiation)
1 - macrophage that has destroyed an antigen becomes an APC
2- complimentary receptors on the surface of a t helper cell bind to the antigen
3 - T helper cells release INTERLEUKINS that stimulate mitosis of the T-helper cell
4 - T helper cells then differentiate
What are the 4 ways T helper cells can differentiate after the initial cell mediated response?
- continue producing interleukins (attract phagocytes)
- become t killer cells
- become t memory cells
- continue producing interleukins (stimulate b cells to divide)
What do t killer cells do?
Produce perforin, perforates the cell membrane of pathogens to destroy them
What do t memory cells do?
stay in blood long term
divide to form t killer cells on reinfection
What are the 4 types of T lympocytes?
killer
helper
regulator
memory
What the role of B lymphocytes in the humoral response?
B cells produce antibodies to neutralise pathogens
Describe the process of humoral immunity
- B cells are triggered when they come into contact with the antigen complementary to their antibodies
- antigen in engulfed and presented on their surface MHCs
- T-helper cell is attracted and selects the b-cell for cloning
- b cells divide and mature into plasma cells (which secret antibodies and neutralise the pathogen) or memory cells (which circulate in the blood for future infection)
Describe the secondary response to infection in terms of b cells
B memory cells detect the antigen (binds to antibodies)
memory cells develop into plasma cells that produce antibodies
Compare plasma cells and memory cells
plasma - short-lived, immediate response, primary response
memory - long-lived, secondary, long-term immunity
Where do T cells mature?
thymus gland
Where do B cells mature?
bone marrow
What type of proteins are antibodies?
quaternary (4 strands)
immunoglobulins
What are the 3 ways antibodies “fight” pathogens?
Agglutination
Neutralise antigens
opsonisation
What is aggultination?
“clumping” pathogens together
too big to enter host cells, immobilised and easier for phagocytosis
What is neutralisation of antigens?
antibodies bind to toxins and block receptors on pathogens so they can’t bind to or enterr host cells
What is opsonisation?
antibodies bind to antigens and “tag” them - marks them for destruction by phagocytosis
ENHANCES PHAGOCYTOSIS
Describe the structure of an antibody
- 4 polypeptide chains (2 short/light chains, 2 heavy/long chains)
- held in Y shape by disulfide bridges
- large area of constant region
- 2 variable regions specific to antigens
Draw the shape of the primary and secondary response graph, marking on the first exposure the second exposure and labelling the axes
revision photo 5
What is an autoimmune diease?
stops recognising self cells and starts to attack and destroy healthy tissue
How are autoimmune diseases treated?
Immunosuppressants
Define antibody
Immunoglobulins produced by B lymphocytes in response to a specific antigen, triggering an immune response
Define APC
Antigen presenting cell
a macrophage that displays foreign antigens
Define clonal selection
The identification of an antibody-producing cell with complementary receptors to the shape of the specific antigen
State the 4 types of immunitty
Natural active
Artificial active
Natural passive
Artificial passive
Give an example of natural active immunity
Antibodies made after an exposure to an infection
Give an example of artificial active immunity
Antibodies made after getting a vaccination
Give an example of natural passive immunity
Antibodies transmitted from bother to baby eg. via breast milk
Give an example of artificial passive immunity
Antibodies made by someone else and injected into you
Describe when active immunity occurs and how long it lasts
direct contact to antigens/pathogens/spike proteins
immunological memory via B and T memory cells
Describe when passive immunity occurs and how long it lasts
antibodies directly introduced into your body
you do not make antibodies yourself
immunity is immediate but does not last
Why are booster vaccines necessary?
- more memory cells produced
- more plasma cells produced if reinfected
- more antibodies produced so stronger fight against pathogen
Why are vaccines given in small doses?
enough to trigger immune response but not overwhelm immune system
What is herd immunity
a critical proportion of a population are vaccinated against a disease reduces spread and protects vulnerable people
Why are diseases difficult to eradicate?
- vaccinations might not work on some people
- some people may be infected before vaccination and spread it
- mutations
- vulnerable can not be vaccinated
- some choose not to be vaccinated
What is antigenetic varabilty?
the formation of new strains of a pathogen as mutations cause changes in antigens thus antibodies and memory cells ineffective
What are antibiotics and what do they do?
Inhibit growth/ destroy bacteria without affecting our cells (selective toxicity)
produced by other living organisms
What are the 2 types of antibiotic
Broad spectrum/targeted
How do antibiotics work?
- inhibition of ell wall synthesis
- disruption of cell wall
- inhibit protein synthesis
- inhibit RNA synthesis
- inhibit nucleic acid synthesis
(generally enzyme inhibitors)
Why do antibiotics not work against viruses?
can’t inhibit cell wall/protein synthesis as they have no cell wall and don’t use their own machinery to produce proteins
How is antibiotic resistance caused?
- –random mutation produces a gene for antibiotic resistance
- –antibiotics are used (selection pressure) natural selection for bacteria that are resistant
- –the number of resistant bacteria increase as they multiply, outcompete the non-resistant strain
- –alleles for resistance passed on through conjugation
What is conjugation?
cells attach to each other through pilli and genes are exchanged
What is MRSA?
carried by 30% on our skin or in our nose
in blood in can cause boils, abscesses and septicaemia
treated with methicillin but now resistant
What is C. difficile?
in the gut of 5%
produces toxins - damages the lining of intestines
causes diarrhoea, bleeding and death
How can we reduce antibiotic resistance?
- minimise the use of antibiotics
- finish every course of antibiotics
- good hygine
- targetted antibiotics where possible
What are medicines?
Drugs used to treat communicable and non-communicable diseases
treat symptoms or cures
Where do we get medicines from?
- naturally occurring compounds in plants/microorganisms that they use to defend themselves
- – developed by complex computer programs to build 3D models and search through libraries of molecules
Why is biodiversity important in medicines and antibiotics?
maintaining biodiversity is important as plants/microorganisms that could go extinct could hold the key to a life-saving drug
What is pharmacogenetics? Give an example
the study of our genome and personalising medicines or treatments based on this
eg. genes alter our side effects to leukaemia treatment, blood is taken and analysed so dose can be given correctly
Give 2 examples of synthetic biology in drugs
nano-technology for delivering drugs
using bacteria as factories to produce drugs
