responding antigen Flashcards
Define an antigen.
An antigen is a unique molecule or part of a molecule that can initiate an immune response.
Define a pathogen.
A pathogen is a disease-causing agent
How is non-cellular defined?
They require a host cell as they cannot reproduce outside a host cell
No metabolic cellular processes (whilst they have DNA or RNA they have no organelles to generate energy or proteins)
Not made of cells
What are prions?
Prions are abnormal infectious proteins.
What is a virus composed of?
Genetic material (DNA or RNA) and protein coat (capsid)
What are examples of chemical barriers and how do they prevent the entry of a pathogen in plants?
Secretion of enzymes
Secretion of toxins e.g. Phytoalexins which are antimicrobial compounds produced by damaged plant cells
Odour chemicals e.g. peppermint that act as natural pesticides
Coffee plants use caffeine to ward off insects
When a plant is wounded resin is secreted which closes the wound over to prevent pathogen entry.
What are examples of physical barriers and how do they prevent the entry of a pathogen in plants?
Intact bark and thick waxy cuticles provide a protective coat through which pathogens cannot enter.
Hair on the leaves and surrounding the stomata prevent the entry of pathogens.
Galls are abnormal swellings at the infection site which limit the movement of the pathogen by trapping it in this area.
Stomata are often sunken within the leaf to prevent pathogens entering.
What is an example of a microbiota barrier in plants?
Rhizosphere is the area around a plant root that is inhabited by a unique population of microorganisms and is influenced by the chemicals released from plant roots, this acts as a microbiota barrier in plants as the naturally occurring bacteria outcompete the pathogenic bacteria in the soil
What is an example of a microbiota barrier in humans?
Many microbes live in a symbiotic relationship with humans these microbes outcompete pathogenic bacteria preventing them establishing colonies in the human body e.g. on the skin or in the alimentary canal.
What are examples of chemical barriers and how do they prevent the entry of a pathogen in humans?
weat secretes both salt and fatty acids which are bacterial inhibitors and prevent pathogen infection.
Saliva and tears secrete lysozymes which are enzymes that break bacterial cell walls, so bacterial cells burst due to osmosis.
The lungs secrete a mucus from goblet cells that helps trap dirt and pathogenic particles, this mucus is then removed via the cilia that pass the mucus up and out of the lungs and nose.
The stomach secretes a strong hydrochloric acid which kills the majority of pathogens that enter via the digestive system.
What are examples of physical barriers and how do they prevent the entry of a pathogen in humans?
Intact skin prevents the entry of pathogens
Hairs in our ears and nose trap foreign particles
Ear wax traps foreign particles
What is a chemical barrier?
some type of secreted chemical that helps prevent the entry of a pathogene
