Communicable Disease Flashcards
What are communicable diseases?
- Can be spread between organisms of the same species or sometimes between different species.
- Spready by PATHOGENS
What are PATHOGENS?
microorganisms which can causes disease.
- HOST ~ the organism which the pathogen infects
FOUR main categories:
- bacteria
- virus
- fungi
- protoctista / protista
Bacteria
- PROKARYOTIC cells
- Once they enter the body, release TOXINS.
- Toxins ~ chemicals which damage host cells and tissues leading to symptoms of the disease
- Divide rapidly by BINARY FISSION
Examples of Bacterial diseases
TUBERCULOSIS:
- affects many part of the body , mostly the LUNGS
- kills the cells and tissues
MENINGITIS:
- infection of the MENINGES ~ the membrane that surround the brain & spinal cord
- The membranes become swollen and may cause damage to the brain & nerves
RING ROT ( plants):
- Ring of decay in the VASCULAR TISSUE
- infect potato tuber and tomato
- Cause leaf wiltering
Viruses
- Much SMALLER than bacteria
- NON-LIVING
- Have no cellular structure
- PREVENT a host cell from functioning normally and can lead to the death of the host cell
- Consist of GENETIC MATERIAL which can be DNA or RNA which is wrapped in a protein structure , CAPSID.
- ATTACHMENT PROTEINS ~ allow the virus to attach to host cells
- Some contain a LIPID MOLECULE
How do viruses REPRODUCE?
- CANNOT reproduce OUTISIDE of a host cell
To reproduce:
- a virus ATTACHES to the host cell and then passes through the CELL MEMBRANE
- COPIES itself using the ENZYMES of the host cell
- Virus particles now LEAVE the host cell and can go on to infect NEW host cells and continue REPRODUCING
Examples of VIRUSES
HIV/AIDS:
- attacks cells in the immune system and comprises the immune response
- caused by infected needles
INFLUENZA (flu):
- Attacks respiratory system
- causes muscle pain & headaches
TOBACCO MOSAIC VIRUS (plants):
- causes mottling & decolouration of leaves
Fungi
- EUKARYOTIC organisms
- Can be UNICELLULAR or MULTICELLULAR
- Obtain NUTRIENTS by releasing enzymes and DIGESTING the material around them
- The PRODUCTS of digestion are then absorbed back into the fungal cells
- Causes DAMAGE to host cells & tissues
- SPORES ~ released when they reproduce and cause fungal diseases to spread very WIDELY
- Some found in REMAINS of dead bodies where they take part in the DECAY process
- PATHOGENIC BACTERIA are found on living organisms where they cause disease
Examples of fungal infections
BLACK SIGATOKA :
- infects plants, mainly BANANAS
- causes leaf spots which reduce yields
RINGWORM:
- infects CATTLE
- growth of fungus in skin withs spore cases erupting through skin to cause a RASH
ATHLETES FOOT:
- growth under skin of feet
- Particularly between the toes
Examples of PROTISTA diseases
BLIGHT:
- Affects tomatoes & potatoes
- causes damage to potato tubers & leaves
MALARIA:
- parasite in the blood
- causes headaches and fever
- can progress to coma and death
- caused by PLASMODIUM
Protocista/ protista
- EUKARYOTIC organisms
- Cause harm by entering host cells and feeding on their contents as they grow
- GIARDIA ~ causes diarrhoea and is transmitted when humans drink water containing infected faeces
- PLASMODIUM ~ causes malaria in humans and is transmitted between humans by mosquitos
Direct transmission and factors that affect these
Direct physical contact :
- hygiene
- e.g washing hands regularly
- cleaning surfaces
Faecal ( contamination of food and drink):
- Washing all fresh food
- Treatment of waste water
- thorough cooking of all food
Droplet infection:
- cover mouth when sneezing or coughing
- using a tissue then disposing correctly
Spores:
- washing skin after contact with soil
- use of a mask
SOCIAL FACTORS that affect transmission
OVERCROWDING:
- Many people living and sleeping together in one house
POOR VENTILATION
POOR HEALTH:
- Particularly those with HIV/AIDS, as they are more likely to contract more diseases
POOR DIET
HOMELESSNESS
MIGRATION :
- Living or working with people who have migrated from areas where a disease is more common
Indirect transmission
Passing a pathogen from hot to new host via a VECTOR.
VECTOR ~ an organism that carries a pathogen from one host to another
PASSIVE DEFENCES of plants against pathogens
These are present BEFORE infection and their role is to PREVENT ENTRY & SPREAD of the pathogen:
CELLULOSE CELL WALL ~ acts as a physical barrier but also can have a variety of chemicals that are activated
LIGNIN THICKENING :
- Prevent water form collecting on the cell surfaces
- pathogens need water to survive
BARK:
- contains chemical defences such as TENNINS
STOMATAL CLOSURE :
- Controlled by guard cells
- when pathogen is detected guard cells close stomata
Callose & Tylose formation
Types of chemical & passive defence against pathogen in PLANTS:
CALLOSE:
- Large polysaccharide
- deposited around the sieve plates
- BLOCKS the flow in the sieve tube
- prevents pathogen from spreading around the plant
TYLOSE:
- Balloon-like swelling or projection
- plugs the vessel so the vessel can no longer carry water
- BLOCKS XYLEM vessels
- contains TERPENES which is TOXIC to pathogens
ACTIVE defences of plants against pathogens
When a pathogen attacks, the plant responds by fortifying the defences already present:
ADDITIONAL CELLULOSE:
- Cell wall becomes thickened and strengthened
DEPOSITION OF CALLOSE:
Between the plant cell wall and cell membrane near the invading pathogen
OXIDATIVE BURSTS:
- Produce highly reactive oxygen molecules capable of damaging the cells of invading organisms
CHEMICAL defences of plants against pathogens
TERPENOIDS:
- Essential oils with antibacterial & antifungal properties
- Can create SCENT e.g menthols by mint plants
PHENOLS:
- Antibiotic & antifungal properties
- TANNINS found in bark inhibit attack by insects
- Bind to salivary proteins & digestive enzymes and DEACTIVATE them
- If a high amount of tannins is digested the insect dies.
ALKALOIDS:
- Nitrogen-containing ~ caffeine, nicotine, cocaine
- Give a BITTER taste
- Inhibit enzymes involve in metabolic reactions e.g protein synthesis
DEFENSINS:
- Small cysteine-rich proteins
- Have broad anti -microbial activity
- Work in plasma membrane of pathogen, inhibiting the action of ion transport channels
HYDROLYTIC ENZYMES:
- Found in spaces between cells
- CHITINASES ~ breaks down chitin in fungal cell walls
- GLUCANASES ~ hydrolyse glycosidic bonds in glucans
- LYSOZYMES ~ degrade bacterial cells walls
Necrosis & Canker
PLANT defences against pathogens that cause DEATH of a part of the plant:
NECROSIS:
- Deliberate cell suicide
- some cells are sacrificed to save the rest of the plant
- Limits the pathogens access to water an nutrients
- stop the pathogen from spreading further
CANKER:
- A sunken necrotic lesion
- in the woody tissue e.g stem or branch
- Causes death of the CAMBIUM TISSUE in the bark
NON-SPECIFIC defences against pathogens in humans
- RAPID
- Prevent pathogens from gaining access to the body
- Are the SAME for ALL pathogens
INCLUDE:
- skin
- mucous membrane
- expulsive reflexes
- blood clotting
- inflammation
OTHERS:
- Wax ~ in ear canal traps pathogens
- Acidic conditions ~ vagina
Skin
- Provides a PROTECTIVE layer for the majority of the body surfaces
- Outer layer ~ EPIDERMIS , consists of LAYERS of cells , mostly…
KERATINOCYTES :
- produced by MITOSIS at the base of the epidermis
- MIGRATE out to the surface of the skin
- Dry out and the CYTOPLASM is replaced by the protein KERATIN.
- Process ~ KERATINISATION
- The keratinised layer of DEAD cells acts as an effective BARRIER to pathogens
Mucous Membrane
- PROTECTIVE layer that lines openings such as trachea in the breathing system.
- Secrete MUCUS which traps microorganisms , these can then be destroyed by PHAGOCYTES
- In the STOMACH , the mucus contains HCl which helps to kill any pathogens in food or water
Lysozymes
MUCOUS MEMBRANE:
- Destroys BACTERIA by digesting the bacterial cell wall
TEARS:
- Prevents pathogens from entering the eye
Also found in SALIVA & LYSOSOMES
Expulsive Reflexes
- pathogens can enter through openings e.g mouth or nose
- Areas prone to attack are SENSITIVE and respond to irritants like toxins with reflexes including:
- Coughing
- Sneezing
- Vomiting
- Diarrhoea
- These SUDDEN EXPULSIONS carry the microorganisms & irritants with it.
Blood clotting
PLATELETS:
- Tiny, short-lived, fragments of cells with no nucleus
- Formed continuously in the bone marrow
- Damage to the blood vessel wall EXPOSES COLLAGEN
- The platelets are ACTIVATED :
- form a PLUG over the damaged
- release CLOTTING FACTORS e.g thrombokinase
- THROMBOKINASE together with Ca2+ ions act on a blood protein called PROTHROMBIN
- Converted into an ACTIVE enzyme called THROMBIN
- which acts on a SOLUBLE protein called FABRINOGEN
- This CATALYSES the formation of INSOLUBLE FIBRIN which forms a MESH , which traps red blood cells to form a BLOOD CLOT.
What occurs after the BLOOD CLOT forms?
- The clot DRIES to form a SCAB
- This PROTECTS the underlying tissue from pathogens while the wound heals
- SKIN CELLS under the scab DIVIDE & REPAIR the damage
- Scab FALLS OFF leaving freshly repaired skin
Inflammation
- When tissue is damaged, MAST CELLS are activated, releasing HISTAMINE.
This causes:
VASODILATION:
- Blood vessels dilate or widen
- increases the supply of blood to the effected area
- causes area to feel HOT and RED
- The increases in temperature reduces the ability of pathogens to REPRODUCE
BLOOD VESSEL PERMEABILITY:
- allows more blood plasma to leave the blood and form TISSUE FLUID
- Causes nearby tissue to swell (OEDEMA) and feel PAINFUL.
EXCESS TISSUE FLUID:
- drained into the lymphatic system where lymphocytes are stored
- The ACTIVITY of these lymphocytes…
- causes swelling of the LYMPH NODES
Types of WHITE BLOOD CELL
Non-specific defences:
PHAGOCYTES~
- Neutrophils
- Macrophages ( also play a role in specific immune system)
Specific defences:
LYMPHOCYTES~
- B
- T
OPSONINS
PROTEINS that attach to FOREIGN molecules and TAG them a foreign.
- Include ANTIBODIES as well as other molecules which are called COMPLEMENTS.
- The surface of pathogens are covered with chemicals
- These FOREIGN CHEMICALS are what opsonins recognise , STICK TO , and tag.
Phagocytosis with NEUTROPHILS
- Neutrophil is ATTRACTED to molecules produced by pathogens ~ CHEMOTAXIS
- RECEPTORS on the neutrophil MEMBRANE now attach to the opsonins
- Pathogen is ENGULFED by ENDOCYTOSIS forming a PHAGOSOME
- LYSOSOMES move towards the phagosome and FUSE with it , forming a PHAGOLYSOSOME.
- HYDROLYTIC enzymes DIGEST pathogen
- The HARMLESS products can be absorbed into the cell
Phagocytosis with MACROPHAGES 1
- Travel in the blood as MONOCYTES
- The foreign molecules on the bacterium surface are ANTIGENS
- Pathogen is ENGULFED into a PHAGOSOME
- LYSOSOMES join to forma PHAGOLYSOSOME
- HYDROLYTIC ENZYMES digest the pathogen
Phagocytosis with MACROPHAGES 2
ANTIGEN PRESENTATION:
- GYLCOPROTEINS from the cytoplasm move to the phagolysosome
- This BINDS to the antigen molecules to form a MHC- antigen complex
- This move to the cell SURFACE MEMBRANE
- the antigens are presented to the EXTERIOR of the cell.
- The macrophages are functioning as an ANTIGEN-PRESNETING CELL
( also play a critical role in the SPECIFIC immune system when presenting antigens to lymphocytes)
Cytokines
- CHEMICAL released by PHAGOCYTES when it engulfs a pathogen
- SIGNALS to phagocytes and other IMMUNE CELLS to move to the site of infection
- Also trigger INFLAMMATION & FEVER
