UNIT 4 7A: First Line of Defence Flashcards
Innate Response
A non-specific defence against a pathogen
First line of defence
The first innate response; consists of physical, chemical and microbiota barriers
Normal Flora
Naturally occurring microorganisms that live in or on animals and plants and do not cause harm or an immune response
Surfactants
Molecules that reduce the surface tension of water and aqueous solutions
Saponin
Soapy compound that occurs naturally in plants; has anti-fungal and antimicrobial properties
Defensins
Proteins that are toxic to microbes
Blood-brain barrier
A barrier of specialised epithelial cells in the brain and spinal cord that prevents pathogens and toxins reaching the neurons
Pathogenic Bacteria
Bacteria that cause harm and an immune response
How many lines of defence does a human have?
3
Which lines of defence make up the innate immune response?
1 and 2
What is the difference between a Plant’s immune response and an Animal’s?
A plant only has the first line of defence, whereas an animal has all three. Every plant cell has to defend itself. It has no circulating immune cells.
Describe how mucus and cilia work together to help defend against pathogens.
Mucus helps to trap a pathogen, and the cilia assist in transporting the mucus and the pathogen towards the mouth. The mucus and the pathogen are swallowed and enter the digestive system, and the pathogen is killed when it encounters the extreme acidic environment of the stomach.
Describe how a plant’s bark acts as a physical barrier
Bark is a thick layer of cells that prevents pathogens entering the plant. The bark also drops away from the plant, taking the pathogen with it.
Describe how natural flora assist in protecting a human and plants against pathogens.
Natural flora compete directly with pathogenic bacteria for space and resources. The successful natural flora do not allow the pathogenic bacteria to grow and replicate (binary fission) and this protects the person or plant from getting sick.
What are two locations where you would expect to find normal flora in humans, and one location where you would expect to find them in plants?
In humans, skin, digestive tract, nose.
In plants: the roots.
Explain why it is important for skin to be intact when acting as a physical barrier for animals
Skin can only act as a physical barrier when it is intact. Any breaks in the skin can act as an entry site for pathogens to enter the body, so the skin would no longer be acting as a physical barrier.
Examples of Physical Barriers in Animals
Intact skin
Mucus
Cilia
Hairs
Examples of Physical barriers in Plants
Thickened cell wall
Thick Bark
Waxy cuticle
Stomata that close
Examples of Chemical barriers in Animals
Lysozyme
Stomach acid
Surfactants in the lungs
Examples of Chemical barriers in Plants
Toxins
Oils
Resins
Saponin
Defensins
Microbiota Barriers in Animals
Normal flora in the gut, on the skin, nose
Microbiota barriers in Animals
Normal flora in the gut, on the skin
Microbiota Barriers in Plants
Normal flora in roots
Role of Physical Barriers
To prevent a pathogen from entering the organism
Role of Chemical barriers
To reduce the pathogen’s ability to grow
Role of Microbiota barriers
To compete for resources/space, preventing pathogen’s growth/reproduction
methods of entry of a pathogen into a host cell
Endocytosis
Membrane Fusion
Gene injection
Methods of release out of a host cell
Lysis
Cell budding
Exocytosis
