4.1.1 Communicable Diseases, Disease Prevention and the Immune System Flashcards
What is gram positive bacteria?
- Looks purple/blue under a light microscope
- Stained with crystal violet
E.g. MRSA
What is gram negative bacteria?
- Looks red under a light microscope
- Stained with safranin
E.g. E. coli
What are the different shapes and examples of bacteria?
- Cocci (spherical) e.g. Staphylococcus aureus that causes acne
- Vibrio (curved) e.g. Vibrio cholerae causes cholera
- Bacilli (rod-shaped) e.g. Escherichia coli causes food poisoning
- Spirilli (spiral) e.g. Helicobacter pylon causes stomach ulcers
What are the characteristics of different shapes of bacteria?
- Cocci have less surface area per volume than bacilli or spirrilum so can survive in dryer environments
- Bacilli and vibrio have a greater SA:V ratio so take up nutrients from dilute solutions more efficiently
- Spirilli move with a corkscrew motion so meet less resistance from surrounding water
How do bacteria reproduce?
- Binary fission
- One bacterium can divide into two bacteria every 20 minutes
What are the problems with bacteria reproducing so quickly?
- Food spoilage
- Spread of disease
How do bacteria cause disease?
- Produce toxins and cause symptoms by cell damage
- Damage cell membranes, enzymes (affecting metabolic activity) or genetic material
- Antigens on bacteria
What are the characteristics of tuberculosis (TB)?
- Caused by bacteria
- Attacks the lungs
- Symptoms include a cough, pain in the chest, coughing up blood, weight loss, fever
What are the characteristics of bacterial meningitis?
- Caused by bacteria
- Symptoms include fever, vomiting, rash on the skin, stiff neck, bruising on skin
What are the characteristics of ring rot?
- Caused by bacteria
- In potatoes and tomatoes
- Plants wilt
- Soft cheese like rotting of the vascular wall
What are the features of a bacteriophage (virus)?
- Injection tube
- Protein coat
- Loose genetic material
- Tail plate
How do bacteriophages invade living cells?
- The virus attaches to a specific host cell
- The genetic material from the virus is injected into the host cell
- The viral genes cause the host cell to make new viruses
- The host cell splits open, releasing the new virus
What are the features of a retro virus (e.g. HIV)?
- Capsid
- RNA + protein
- Enzymes (reverse transcriptase)
- Matrix
- Envelope (phospholipid bilayer)
- gp120 and gp41 - glycoprotein spike specific (complementary to CD4 receptor)
How does a retrovirus replicate?
- Single stranded RNA instead of DNA
- Reverse transcriptase enzyme uses RNA as a template to make SSDNA
- DNA polymerase enzyme then makes double stranded DNA
- This is then attached to the host DNA
- Host cell is now able to make new viruses which travel to the host membrane to be released
- Exocytosis gets it out
What are the characteristics of HIV/AIDS?
- Caused by viruses
- In humans
- Symptoms include fever, weakness, weight loss, swollen lymph glands and diarrhoea
What are the characteristics of influenza?
- Caused by viruses
- In animals
- Symptoms include fever, chills, irritation of upper respiratory tract, cough and sore throat
What are the characteristics of tobacco mosaic virus?
- Caused by viruses
- In plants
- Discolouration of the leaves of the tobacco plant
What are the features of a fungus cell?
- Cell wall
- Nucleus
- Cell membrane
- Cytoplasm
- Vacuole
- Mitochondria
What are the characteristics of cattle ringworm?
- Caused by fungi
- Circular ring shaped scales or plaques
- Flat patches with raised border
- Itchy skin
What are the characteristics of athlete’s foot?
- Caused by fungi
- In humans
- Symptoms include scaly, peeling cracked skin between toes, itchy feet, inflamed skin
What are the characteristics of black sigatoka?
- Caused by fungi
- In bananas
- Symptoms include reddish brown spots and streaks on underside of leaves
What are the features of protoctista?
- Uncellular
- Have a nucleus
E.g. amoeba and plasmodium (plasmodium falciparum causes malaria)
What are the characteristics of late blight in potatoes/tomatoes?
- Caused by protoctista
- Symptoms include brown and rotting, shriveled leaves, dark brown legions on leaves, yellow leaves
What are the characteristics of malaria?
- Caused by protoctista: plasmodium
- Symptoms include fever, chills, sweating, headache, muscle pain and yellow skin/whites of eyes
What are the methods of direct transmission of animal communicable pathogens?
- Direct contact
- Innoculation
- Ingestion
How does direct contact transmit animal communicable pathogens?
- Contact with body fluids (e.g. kissing)
- Skin to skin (ringworm, athlete’s foot)
- Microbes from faeces (diarrhoea diseases)
How does innoculation transmit animal communicable pathogens?
- Break in the skin
- Animal bite
- Puncture wound/sharing needles
How does ingestion transmit animal communicable pathogens?
- Taking in contaminated food or drink
- Transferring pathogens from hand to mouth
What are the methods of indirect transmission between animals?
- Fomites
- Droplet infection
- Vectors
How do fomites transmit animal communicable pathogens?
- Inanimate objects (e.g. bedding, socks, cosmetics)
- Carry and spread pathogens
How does droplet infection transmit animal communicable pathogens?
- Droplets of saliva and mucus are expelled from your mouth as you talk, cough or sneeze
- Others breathe this in and are contaminated
How do vectors transmit animal communicable pathogens?
- Transmits disease from one host to another
E.g. Mosquitos transmit malaria, rat fleas transmit bubonic plague, water can transmit diarrhoea diseases
What factors increase the transmission of communicable disease in animals?
- Bad diet
- Socioeconomic factors
- Poor disposal of waste
- Culture
- Climate change
- Infrastructure
- Drought
- Famine
- Compromised immune system (e.g. HIV/AIDS)
- Overcrowding
How are the eyes a primary non-specific defence?
- Protected by tears and REM (rapid eye movement)
- REM pushes microbes to front of eye
- Tears contain water, salts and lysosomes
- Microbes die in salty conditions
How is the nose a primary non-specific defence?
- Full of hair and mucus which trap microbes and then you blow it out or shift it to the back of your throat and swallow it
- Mucus contains lysozymes which destroy bacteria and fungal cell walls and phagocytes
How is the mouth a primary non-specific defence?
- Saliva contains antibacterial enzymes
How are the ears a primary non-specific defence?
- Wax traps pathogens
How is mucus in the airways a primary non-specific defence?
- Mucus traps microbes and ciliated epithelial cells waft it to the back of the throat
How are tears/sweat a primary non-specific defence?
- Contain antibacterial enzymes
How is skin a primary non-specific defence?
- Massive protective barrier covering the entire body
- Prevents entry
- Produces sebum which inhibits growth of pathogens
How is the gut a primary non-specific defence?
- Good gut bacteria out compete the bad
How is the vagina a primary non-specific defence?
- Female cycle ensure that most microbes are ejected from the vagina every 28 days with the uterine wall
How is the penis a primary non-specific defence?
- Urine is a mixture of water and urea
- A toxic substance made from products of broken down protein
- Microbes don’t live in these conditions
- Urine contains lysozymes
How is the anus a primary non-specific defence?
- Most microbes are ejected from the anus with faeces
How is the stomach a primary non-specific defence?
- Stomach acid is pH 2
- Low pH kills harmful microbes
How is blood clotting a primary non-specific defence?
- Blood clots to prevent pathogens from getting in
- Thromboplastin is released which causes the clot
- Seratonin contracts capillaries to reduce blood loss
How are expulsive reflexes a primary non-specific defence?
- Coughing and sneezing
- Expels foreign objects automatically
How is inflammation a non-specific defense?
- Mast cells in damaged cells release histamines and cytokines
- Histamines make blood vessels dilate and leaky, causing localised heat, redness and swelling
- Prevents pathogens reproducing
- Cytokines attract phagocytes which will engulf and digest pathogens
How is a fever a non-specific defense?:
- Cytokines are released when a pathogen has invaded
- Your hypothalamus detects this and raises your body temperature
- Most pathogens reproduce best at 37°C or below
- The specific immune system works faster at higher temperatures
How are phagocytes a non-specific defense?
Neutrophils:
- Have a lobed nucleus
- Takes approximately 10mins to engulf and destroy pathogens
- Can get through pores in capillaries
Macrophages:
- Have a round nucleus
- When the pathogen is destroyed its antigens combine with glycoproteins in the cytoplasm to form an MHC (major histocompatibility complex)
- This takes the antigen to the cell surface membrane and is now an APC (antigen presenting cell and can stimulate the specific response
- APCs are needed for T and B lymphocytes
What is the process of phagocytosis?
- Phagocyte recognises the antigens on invading pathogens as foreign or by chemicals/toxins
- The cell membrane of the phagocyte fuses around the pathogen, engulfing it into a vesicle called a a phagosome
- A lysosome fuses with the vacuole to form a phagolysosome and empties its digestive enzymes to hydrolyse the pathogen
- Antigens are present on the cell surface membrane (APC), useful products are taken into the cytoplasm by diffusion/active transport and wasted products are exocystosed
What is the humoral response of B lymphocytes?
- Helper T cells release interleukins to activate B cells (cell signaling)
- Clonal selection means the correct antibody is selected for cloning
- B cell matures in bone marrow
- Clonal expansion means clones of plasma and memory cells are made by mitosis
- Forms plasma cells which produce and secrete antibodies (only live for a few days) into the blood steam
- Forms memory cells which remain in lymph nodes to respond rapidly if the same type of pathogen invades again
What are killer T cells?
- Attach to pathogenic cells
- Perforins are released
- Lysis of pathogen occurs
What is the cell-mediated response of T lymphocytes?
- T helper cells have receptors on their surface which attach to the antigens on an APC
-Helper T cells multiply by mitosis so cells are identical with the specific receptor - Makes large numbers of clones which differentiate
What are helper T cells?
Secrete interleukins to activate other T and B cells
What are memory T cells?
Remain in lymph nodes to respond rapidly if the same type of pathogen invades again
What are regulator T cells?
Slow down and stop the immune reaction after about 1 week
What are the characteristics of the primary response?
- Slower
- Pathogen enters the body for the first time
- Not many B lymphocytes that can make the correct antibody
- Show symptoms
- Memory cells produced
- T lymphocytes record the antigen on the pathogen
- B lymphocytes remember specific antibodies
- There is clonal selection and expansion but it is slow
What are the characteristics of the secondary response?
- Faster
- Same pathogen enters the body
- Clonal selection happens faster
- Memory B lymphocytes divide into plasma cells that produce the correct antibody
- Memory T lymphocytes divide and kill pathogens
- May not show symptoms
What is an antigen?
- A protein on the surface of a pathogen
- Initiates an immune response by causing antibody production
What is an antibody?
Protein made by a B lymphocyte in response to an antigen
What is the structure of an antibody?
- Variable region
- Contrast region
- Antigen binding site
- Light chain
- Hinge region
- Disulphide bonds
- Heavy chain
What is the variable region?
- Complementary to a particular antigen
- Depends on the plasma cell
- Varies on different antibodies
- Forms antigen binding site
What is the constant region?
- Same in all antibodies
- Site where it can bind to receptors on an immune system cell
What is the hinge region?
- Allows flexibility when antibody binds to antigen
What is the heavy chain?
- Contains the site at which the antibody can bind to a cell
What are opsonins?
Antibodies that bind to antigens and act as markers for phagocytes
What are agglutins?
Bind to antigens and cause clumping which prevents them from entering body/host cells
What are anti-toxins?
- Bind to/neutralise toxins to prevent harm to human cells
- Phagocytes then engulf the toxin-antibody complex
What is natural active immunity?
- Immunity provided by antibodies made in the immune system as a result of infection
- Suffers once and then is immune
E.g. chickenpox
What is artificial active immunity?
- Immunity provided by antibodies made in the immune system as a result of vaccination
E.g. TB and influenza
What is passive natural immunity?
- Antibodies provided via the placenta or via breast milk
- Baby is immune to diseases to which the mother is immune
- Useful when the baby’s immune system is still developing in the first year of their life
What is artificial passive immunity?
- Immunity provided by injection of antibodies made by another individual
E.g. hepatitis A and B
What are the differences between active and passive immunity?
Active:
- Exposure to antigen
- Takes time for protection to develop
- Long term protection
- Memory cells are produced
Passive:
- No exposure to antigen
- Protection is immediate
- Short term protection
- Memory cells are not produced
What is an autoimmune disease?
When the immune system is unable to recognise its own cells and launches an immune response to attack a part of the body
What is lupus?
- Can affected any part of the body
- Causes swelling and pain
- May be associated with antibodies that attack certain proteins in the nucleus in cells and affected tissues
- Symptoms include joint/muscle pain, extreme tiredness and rashes
- Inflammation can cause severe damage to heart, lungs and kidnets
- More common in women and those with Black African, Carribean and Asian ancestries
What is arthritis?
- Painful inflammation of a joint
- Cause in uncertain but starts with antibodies attacking the membranes around the joint
- Rheumatoid arthritis is autoimmune but there are other types (e.g. osteoarthritis)
- 1% of the UK is affected
- Women, smokers and those with an RA family history are at a higher risk
- Most common in wrists, hands and feet
- Typically affects joints symmetrically
- Causes join pain, stiffness, fatigue, fever, poor appetite and swelling
- Synovium becomes sore/inflamed and releases chemicals that damage bones, cartilage, tendons and ligaments
- Joints lose shape and alignment
What is herd immunity?
- Where unvaccinated people are protected because the occurrence of the disease is reduced by the number of people who are vaccinated
What is a vaccine?
Stimulates an immune response so that immunity is achieved, usually a dead or weakened pathogen or an antigen
What is immunisation?
The process whereby a person is made immune or resistant to an infectious disease, typically by the administration of a vaccine
What is an epidemic?
A rapid spread of disease through a high proportion of the population
What is a pandemic?
An infectious disease that spreads across continents
What is antigenic variability?
- Antigens of some pathogens are constantly changing
- Each antigen causes its own immune response
What is the source and action of penicillin?
- Originally from would growing on melons
- Antibiotics (first effective treatment
- Inhibits synthesis of bacterial cell walls
What is the source and action of docetaxel
- Yew trees
- Treatment for breast cancer
- Induces cell death by mitotic catastrophe
What is the source and action of aspirin?
- Willow bark
- Pain killer
- Anti-coagulant
- Anti-inflammatory
- Anti-pyretic
What is the source and action of prialt?
- Venom of a cone snail from oceans near Australia
- Painkiller (1000x more effective than morphine)
What is the source and action of vancomycis?
- A soil fungus
- Very powerful antibiotic
What is the source and action of digoxin?
- Foxgloves
- Treats atrial fibrillation and heart failure
What are pharmacogenetics?
- Testing people’s genome to detect whether or not a drug will work
- Doctors can prescribe drugs that will work rather than the ‘one fits all’ system
- Big advances for breast cancer patients
- Herceptin is only prescribed is cancer cells are found to have lots of receptors that are complementary
What is synthetic biology?
Development of molecules that mimic aspects of biology
E.g. enzymes, pigments, bacterial cells
What are antibiotics?
- Medicinal substance used to destroy bacteria inside the body
- Works by bacteria ingesting them and damaging cell structure
- Viruses are inside a host (so no structure to damagae)
What causes antibiotic resistance?
- Overuse of antibiotics (selection pressure)
- Not finishing a course of antibiotics
How does antibiotic resistance happen?
- A random mutation occurs in some bacteria which fives them a resistance to the antiobiotic
- Bacteria that are not resistant die
- Bacteria with resistance survive and reproduce by binary fission
- Resistant gene is passed onto the next generation
- Whole population becomes resistant
What are the problems with antibiotic resistance?
- Resistant strains are hard to treat
- Hard to find new antibiotics and treatments
What is MRSA?
- Stands for methicillin-resistant staphylococcus aureus
- Gram positive bacteria
- Usually live harmlessly on skin but can cause serious infection inside the body
- Patients with supressed immune systems are particularly susceptible
What is Clostridium difficile?
- Infects bowel and cause diarrhoea
- Found harmlessly in the digestive system of 1 in 30 adults and kept under control by other bacteria
- Some antibiotics interfere with the balance of bacteria so C. difficile multiples and produces toxins
- Gram positive bacteria
What are the methods of direction transmission between plants?
Direct contact:
- Healthy plant touches any part of an infected plnt
What are the methods of indirect transmission between plants?
Soil contamination
- Infected plants often leave pathogens in the s
oil which can affect the next crop
Vectors:
- Healthy part of plant touches any part of an infected plant (wind, water, animals, humans)
What factors increase the transmission of communicable disease in plants?
- Climate change
- Overcrowding
- Planting varieties susceptible to disease
- Poor mineral nutrition (specifically micronutrients)
- Damp and warm conditions (microorganisms can grow)
What are the physical defences in plants?
- Cellulose cell wall is a physical barrier
- Lignin thickening of cell walls makes them waterproof and indigestible
- Waxy cuticle prevents water from collecting on the surface
- Guard cells can close the stomata
- Callose is a large polysaccahride that is deposited in sieve tubes at the end of the growing season and blocks the flow so pathogens can’t spread
What are chemical defences in plants?
- Terpenoids have antibacterial and antifungal propteries
- Alkaloids are N containing compounds with a bitter taste which stop herbivores feeding on them and less grazing means less exposure to pathogens
