4.1 - C - Communicable Diseases Flashcards
Define pathogen
An organism that causes disease
What are the 4 types of pathogen?
Bacteria
Fungi
Protoctist
Virus
Explain what bacteria are and do and give 2 examples
Prokaryote Smaller than eukaryotes Reproduce rapidly Damage cells by releasing toxins Eg: tuberculosis, ring rot in potatoes
Explain what fungi are and do and give 2 examples
Often lives in skin
Reproductive hyphae grow into skin and release pores
Hyphae form a mycelium
Lives in vascular tissue (plants) to gain nutrients (from xylem and phloem)
Hyphae release extracellular digestive enzymes to break down cellulose
Eg: black Sigatoka (bananas), ring worm
Explain what proctosits are and do and give 2 examples
Enter hosts and feed on contents of cells
Eg: potato blight, malaria
Explain what viruses are and do and give 2 examples
They invade cells and take over genetic machinery
The cause cells to reproduce copies of the virus
The host cell bursts and new viruses are released, the cycle repeats
Eg: HIV, influenza
What are the 2 types of ways diseases can be transferred
Direct
Indirect
Give 5 examples of direct transfer of diseases
Physical contact Airborne Spores Sneezing/coughing etc. Water/food
Give 1 example of indirect transfer of diseases
Vectors (ie. mosquitoes)
Give 7 factor which affect disease transmission
Homelessness Human migration Poor ventilation Poor health Poor diet Poor hygiene Overcrowding
Explain tuberculosis and the organism that causes it
A disease that affects many parts of the body, killing the cells and tissues; the lungs are most often affected
Bacteria:
Mycobacterium tuberculosis
Explain bacterial meningitis and the organism that causes it
Infection of the meninges - the membranes that surround the brain and spinal chord; the membranes become swollen and may cause damage to the brain and nerves
Bacteria:
Neisseria meningitidis or Streptococcus pneumonia
Explain ring rot (in plants) and the organism that causes it
Ring of decay in the vascular tissue of a potato tuber or tomato, accompanied by leaf wilting
Bacterium:
Clavibacter michiganensis subsp. sepedonicus
Explain HIV/AIDS and the organism that causes it
Attacks cells in the immune system and compromises the immune response
Virus:
Human immunodeficiency virus
Explain influenza and the organism that causes it
Attacks the respiratory system and causes muscle pains and headaches
Virus:
From the Orthomyxoviridae family - “flu” viruses
Explain tobacco mosaic virus and the organism that causes it
Causes mottling and discolouration of leaves
Virus:
Tobacco mosaic virus
Explain black sigatoka (bananas) and the organism that causes it
Causes leaf spots on banana plants reducing yield
Fungus:
Mycosphaerella fijienis
Explain blight (tomatoes and potatoes) and the organism that causes it
Affects both leaves and potato tubers
Protoctistan:
Phytophtora infestans
Explain ringworm (cattle) and the organism that causes it
Growth of the fungus in skin with pore cases erupting through the skin causing a rash
Fungus:
Trichophyton verrucosum
Explain athlete’s foot and the organism that causes it
Growth under the skin of feet - particularly between the toes
Fungus:
Trichophyton rubrum
Explain malaria and the organism that causes it
Parasite in the blood that causes headaches and fever and may progress to coma and death
Protoctistan:
Plasmodium falciparum
What are the 4 stages of a pathogen’s life cycle?
Travel from 1 host to another (Transmission)
Entering the host’s tissues
Reproducing
Leaving the host’s tissues
Define direct transmission
Passing a pathogen from host to new host with no intermediary
Define indirect transmission
Passing a pathogen from host to a new host, via a vector
Define transmission
Passing a pathogen from an infected individual to an uninflected individual
What is a vector?
An organism that carries a pathogen from one host to another
Define inflammation
Swelling and redness of tissue caused by infection
What are coughing, sneezing and vomiting examples of?
Expulsive reflexes
Why are primary defences non-specific?
They can prevent more diseases
What is an expulsive reflex?
When irritation causes a reaction, expelling the pathogen
What do histamine and anti-histamine do?
Histamine - causes inflammation, allows immune system to act
Anti-histamine - reduces inflammation
Define callose
A large polysaccharide deposit that blocks old phloem sieve tubes
What do plants not have?
An immune system
What are the 2 types of passive defence in a plant?
Chemical and physical
Give 5 examples of passive defences
Cellulose cell wall - physical barrier waterproofed by lignin and contain tannins
Waxy cuticle - prevents water collecting which can contain pathogens
Bark - physical barrier, contains chemicals which will work against pathogens
Tylose formation - tylose is a balloon like projection which fills the xylem, acts as a plug, prevents the spread of pathogens. Has high levels of terpenes which are toxic to many pathogens.
Callose
What is the one type of active defence in plants?
Chemical
Give 4 things active defence in plants include
Cell walls become thickened and strengthened with additional cellulose
Deposition of callose between the plant cell wall and cell membrane near the invading pathogen
Oxidative bursts damage cells of invading organisms
Increase in production of chemicals
Give 5 chemicals used in active defence in a plant
Terpenoids - Range of essential oils with antibac and anti fungal properties. Also creates scents.
Phenols - Antibac and anti fungal properties. Tannins in Bari inhibit insect’s attacks. Pathogen transmission drops by high amounts of tannins ingested by insects, causing death.
Alkaloids - nitrogen-containing compounds. Give herbivores a bitter taste. Some inhibit protein synthesis.
Defensins- defensive proteins
Hydrolytic enzymes
(See book)
What are tannins?
Chemical defences which are activated if a pathogen is detected
What is canker?
A sunken necrotic lesion in the woody tissue such as the main stem or branch. It causes death of the cambium tissue in the bark.
What is necrosis?
Deliberate cell suicide. Sacrifices are made to save the rest of the plant. Stops spread of pathogens.
What are primary defences?
Those that prevent pathogens entering the body
What is a mucous membrane?
Specialised epithelial tissue covered by mucus
What do the clotting factors activate?
An enzyme cascade
What does histamine do?
Causes vasodilation - makes capillary walls permeable to phagocytic white blood cells and proteins
Give 8 examples of primary defences
Skin
Blood clotting/skin repair
Mucous membranes
Coughing/sneezing/vomiting - expulsive reflexes
Inflammation
Eyes protected by antibodies and enzymes in tear fluid
Ear wax
Mucus plug in the cervix of the female reproductive system, maintaining acidic conditions in the pussy
What is an antigen-presenting cell?
A cell that isolates the antigen from a pathogen and places it on the plasma membrane so that it can be recognised by other cells in the immune system
Define clonal selection
Selection of a specific B or T cell that is specific to the antigen
What are cytokines?
Hormone-like molecules used in cell signalling to stimulate the immune response
What is a neutrophil?
A type of white blood cell that engulfs foreign matter and traps it in a large vacuole (phagosome) which fuses with lysosomes to digest the foreign matter
What are opsonins?
Proteins that bind to the antigen on a pathogen and then allow phagocytes to bind
Antibodies that make it easier for phagocytes to engulf the pathogen
What is the purpose of secondary defence?
To combat pathogens that have entered the body
Define phagocytosis
The first line of secondary defence.
Specialised cells in the blood and tissue fluid engulf snd digest pathogens.
What are lymphocytes and phagocytes involved in?
Lymphocytes - specific immune response
Phagocytes - non-specific response
Describe what happens in phagocytosis
Neutrophil binds to opsonise attached to antigen of the pathogen
Pathogen engulfed by endocytosis forming a phagosome
Lysosomes fuse to the phagosome and release lyric enzymes into it
After digestion, the harmless products can be absorbed by the cell
What is the first line of secondary defenceL
Phagosytosis
What are macrophages a type of?
Phagocyte
Explain macrophages
Lager cells, made in bone marrow. Travel in blood as monocytes then settle in body tissues.
They initiate responses to invading pathogens.
When engulfing pathogens, they don’t fully digest them.
The antigen on the pathogen is moved to a special protein complex on the surface of the cell. It becomes the antigen-presenting cell.
It exposes antigen on its surface so other cells recognise it.
What are the 2 types of antigen immunity?
Antigen presentation
Specific immune response
Explain antigen presentation
Antigen presenting cells move around the body where it can come into contact with specific cells that can activate full immune response. Involves T and B lymphocytes
Explain specific immune response
Clonal selection produces antibodies that combat specific pathogens and memory cells that will provide long-term immunity.
Define antibody
Specific proteins released by plasma cells that can attach to pathogenic antigens
Define clonal expansion
An increase in the number of cells by mitosis cell division
What are interleukins?
Signalling molecules that are used to communicate between different white blood cells
What are the 4 types of cells that T lymphocytes develop/differentiate into and what are their functions?
T helper cells - release cytokines that stimulate B cells to develop and stimulate phagocytosis by the phagocytes.
T killer cells - which attack and kill host-body cells that display the foreign antigen
T memory cells - which provide long-term immunity
T regulator cells - which shut down the immune response after the pathogen has been successfully removed. They are also involved in preventing autoimmunity
What are the 2 types of cells that B lymphocytes develop into and what are their functions?
Plasma cells - which circulate in the blood, manufacturing and releasing the antibodies
B memory cells - which remain in the body for a number of years and act as the immunological memory
What are autoimmune diseases?
Give 2 examples
When the immune system attacks a part of the body.
When antibodies start to attack our own antibodies.
Lupus, arthritis
What are agglutinins?
Antibodies that cause pathogens to stick together
What are anti-toxins?
Antibodies that render toxins harmless
How many polypeptide chains are in an antibody?
How are they held together?
4
Disulphide bonds
What is the purpose of the constant region?
For binding to phagocytes
What is the purpose of the hinge region?
Allows flexibility
What is the purpose of having more than one variable region?
Allows attachment to more than one antigen - agglutination
What is the purpose of the variable region?
Binds to antigens
Define active immunity
Where the person’s own immune system is activated and manufactures its own antibodies
Define passive immunity
Immunity acquired without the activation of the lymphocytes, it’s achieved when antibodies are passed to the individual from another person’s immune system (breastfeeding, injections, etc.)
Define natural immunity
Immunity gained in the normal course of living
Define artificial immunity
Immunity achieved as a result of medical intervention/deliberate exposure to antibodies or antigens
Define epidemic
A rapid spread of disease through a high proportion of the population
Explain ring vaccination
Vaccinating all people living with or near the victim
It contains the spread in a ring
It requires people to report victims
Explain nerd vaccination
Vaccinating all people at risk
Stops infection spreading
Give an example of natural active immunity
As a result of infection
Give a result of artificial active immunity
Injection of weakened antigens
Give an example of natural passive immunity
Across the placenta/breast milk
Give an example of artificial passive immunity
Injections of antibodies
Give 7 reasons why people may choose not to get immunised
Too busy/cba Media scare stories Concerned about side effects Allergic to vaccine Fear of needles Religious reasons Vaccine is expensive
Give 3 reasons why governments want people to be vaccinated (other than direct health benefits)
Prevention of disease - less sick days, less harm to economy
Costs less to vaccinate than treat
Health service may not cope if lots get infected
Define antibiotic
A chemical which prevents the growth of microorganisms
They can be antibacterial or antifungal
Define personalised medicine
The development of designer medicines for individuals
Define synthetic biology
The re-engineering of biology. This could be the production of new molecules that mimic natural processes, use of natural molecules to produce new biological systems that do not exist in nature.
Give 3 reasons why new drugs are needed
New diseases are emerging
There are still many diseases for which there are no effective treatments
Some antibiotic treatments are becoming less effective
