Diseases, Communication and Immune System Flashcards
Definition of pathogen
An organism which lives on or inside another organism, and causes a disease
Definition of toxin
A substance which is produced by a living organism, typically a pathogen, which is poisonous to the cells of another organism
Definition of a vector
An animal which carries a pathogen in its body and transmits it, but it is not the main host of the pathogen.
Symptoms of a flowering plant infected with Tobacco Mosaic Virus
Leaf tissue is mottled, with brown marks Fruit is slower to ripen Leaf tissues may become yellow and die Leaves curl at the edges Reduced seed/ fruit yield
What is HIV/AIDS and how does it cause disease
It is a virus
The pathogen infiltrates and lives inside T-helper cells, gradually weakening the immune system
What is Bacterial Meningitis and how does it cause disease
Bacterium
The pathogen replicates in the meninges of the brain, causing swelling; can spread into the blood where it leads to septicaemia
What is Athlete’s foot and how does it cause disease
Fungus
The pathogen lives on and digests damp skin around the toes, causing a red rash
What is Malaria and how does it cause disease
Protoctist
The pathogen invades red blood cells and liver, causing fever and vomiting and weakening the body’s immune system.
How does HIV/AIDs spread
Direct (sexual) contact
Breaks in skin genitals
How does Ebola spread
Contact with bodily fluids including sexual contact
How can an injection cause diseases
Through contaminated needles
How does ingestion cause diseases
Eating infected food
vectorborne transmission
Stagnant water-> (direct transmission): drinking water contaminated with faeces which will lead to cholera
Bites from insects etc- a mosquito bite could lead to Malaria if the mosquito carries the pathogen
Fomites transmission
Particles of dead/skin/ hair in bedding- lead to Athlete’s foot
Airborne transmission
Through coughing and sneezing, mucus droplets are spread in air
This can lead to influenza
Examples of direct transmission
Ingestion
Direct contact - both sexual and skin
Exposed cuts
Injection
Examples of indirect transmission
Vector borne
Airborne
Fomites
Why might climate change increase the transmission of a disease
Increasing global temperatures mean that some vectors, such as Zika-virus-carrying mosquitoes or tsetse flies, have a broader range in which they can live and breed, making transmission more likely.
Why might living in a refugee camp increase the transmission of a disease
Refugee camps are typically overcrowded, which makes transmission of airborne diseases more likely, since people are often in close contact. In addition, they often have poor sanitation- this means that diseases spread by contact with contaminated food or water are more likely.
Plant primary defences
Bark on stem provides stability
waxy cuticle on the upper surface on the leaves waterproofs it
However, some pathogens do still manage to access the plant. Infected parts of the plant can be sealed off using a polysaccharide known as callose, which closes the plasmodesmata (gaps) between cells and also prevent movement throguh the phloem by blocking the sieve end plates.
Chemicals plants use as defence mechanisms, and how does it work
Saponins: chemicals with detergent-like properties that disrupt the cell membranes of fungal cells
Phytoalexins: disrupts the metabolism and cellular structure of fungi and bacteria.
Caffeine: inhibits enzymes in the nervous systems of insects, causing paralysis.
Other ex: cyanide, gossypol, pyrethrins, chitinase
main primary defences the human body uses to prevent the entry of pathogens
Skin tissue is tough and difficult to break through
Blood clotting rapidly blocks a point of entry for pathogens
Mucus in the throat traps pathogens, which are brushed upwards by the cilia and swallowed
Coughing and sneezing may remove potential pathogens from the airways
Inflammation restricts the movement of pathogens from the airways.
Lysozymes (digestive enzymes) are produc3d in tears and urine.
Stomach acid has a low pH which kills or inactivates many pathogens.
Why do histamines increase the temperature around a site of infection
Makes it more difficult for pathogens to reproduce, since human pathogens typically have a preferred temperature that’s the same as core body temperature
Process of blood clotting
Platelets are activated by damaged tissue
Thromboplastin is released into the area around the wound
The enzyme causes prothrombin to be converted into thrombin
This compound converts the precursor protein fibrinogen into its active form
Fibrin produces a layer of fibres over the wound, stopping the movement of pathogens.
New skin is created beneath the protein mesh.
How does neutrophils destroy pathogens
Neutrophils engulf a pathogen by surrounding it with the neutrophil membrane, and the ‘budding off’ part of the membrane to form a vesicle. Then they digest the pathogen using enzymes called lysozymes.
When does neutrophils destroy pathogens
Occurs in the blood or in an infected tissue once an infection has been recognised.
How does phagocytes find pathogens and damaged cells
Pathogen and dead or damaged cells produce waste products that act as attractants to the phagocytes, the phagocyte moves towards the pathogen or cell and uses receptors on its cell-surface membrane to attach to the surface of the pathogen or cell.
Pathogens also recognise and digest cells which have been marked by opsonins- a broad range of marker molecules which include antibodies.
How does a phagocyte engulf and destroy a pathogen
When the phagocyte engulfs the pathogen, the pathogen is then contained within a vesicle called a phagosome. Lysosomes within the phagocyte then move towards and fuse with the vesicle, releasing lysozymes into the phagosome. The lysozymes hydrolyse the cell walls of the pathogens, destroying the pathogen.
What happens to the breakdown products of the pathogen
The soluble breakdown products are absorbed into the cytoplasm of the phagocyte.
Where does a Plasma cell mature and its function
Bone marrow
Produces huge numbers of antibodies which trap pathogens and encourage phagocytosis.
Where does B-memory cell mature and its function
Bone marrow
Stays in immune system for years, and creates plasma cells when exposed to a specific antigen.
Where T-helper cell mature and its function
Thymus gland
Had receptors which bind to antigens on antigen-presenting cells; produces interleukins which signal to various other immune cells.
Where does a T-regulator cell mature and its function
thymus gland
Able to regulate the immune system and suppress it to stop autoimmune responses
Why are interleukins described as immune response modulators
Interleukins are chemicals which signal between different white blood cells, and affect the immune response. For example, the interleukins produced by T-helper cells encourage the creation of T-killer cells, and make both phagocytes and plasma cells more active. However, interleukins are also involved in the suppression of the immune response by T-regulatory cells.
