4.1 Biodiversity, Evolution And Disease Flashcards
Describe the features of fungi
•Live under the skin
Describe the features of bacteria
- reproduce rapidly
* cause disease by damaging cells/releasing waste products/toxins
Describe the features of viruses
•Invade cells + take over genetic machinery + other organelles of cell
E.g HIV
Describe the features of protoctista
•Enter host cells + feed on contents as they grow
What is a pathogen
An organism that causes disease
What are the different ways diseases are transmitted?
Vectors
Describe how diseases are transmitted through vectors
- Organisms e.g insects that transmit parasites from one host to another
- food air water
What are the passive (physical) defences plants have against pathogens?
- Cellulose cell wall - contains chemical defences
- Bark - chemical defences
- Callose deposition
What is callose?
A large polysaccharide that blocks the flow in the sieve tube, prevents pathogen spreading around plant.
Name the different primary defences against pathogens in animals
- Skin
- Blood clotting + skin repair
- Mucous membranes
- Coughing + sneezing
- Inflammation
How does the skin act as a primary defence?
Epidermis (outer layer of skin) contains dead skin cells which undergo keratinisation: they dry out and are replaced by the protein keratin.
The keratinised layer of dead cells acts as an effective barrier to pathogens.
How does blood clotting and skin repair act as a primary defence?
Platelets release clotting factors that cause an enzyme cascade that forms a clot and eventually a scab.
How do mucous membranes act as a primary defence?
Protects surfaces at risk of infection.
Most mucous swallowed and pathogens killed by acidity of stomach.
How does coughing and sneezing act as a primary defence?
respond to irritant caused by microbes/toxins by attempting to expel them.
How does inflammation act as a primary defence?
- Histamine is released and causes vasodilation
- white blood cells leave blood and enter tissue fluid
- opsonins released and attach to neutrophil
- engulfs the pathogen in phagosome (capsule)
- lysosomes then destroys the bacteria
What is a phagocyte
The first line of secondary defence, specialised cells in the blood and tissue fluid engulf + digest the pathogens
What are the 2 types of phagocytes
Neutrophils:
Nucleus is split into multiple parts + connected together so it’s more flexible
Macrophages:
Do not move quickly
Link with immune defence
Stores the antigens of pathogens
How do phagocytes engulf pathogens
- macrophages or neutrophils recognise invading bacteria as pathogens
- cell membrane of macrophage/neutrophil fuses around a single bacterium, trapping it inside a cellular compartment called phagosome
- Opsonins (non-specific antibodies) released
- Once pathogen is inside phagosome capsule lysosomes destroy bacteria and keep useful parts, expelling the rest.
What is a T helper cell?
cells that release signalling molecules to stimulate immune response
What is a T killer cell?
Cells that attack or destroy our own body cells that are infected by pathogen
What is a T/B memory cell?
Cells that remain in the blood for a long time, providing long-term immunity
What is a T regulator cell?
Cells that are involved with inhibiting or ending the immune response
What are antibodies?
Specific proteins released by plasma cells that can attach to pathogenic antigens.
What are the 4 main stages in the immune responce
- phagocytes engulf pathogens
- phagocytes activate T lymphocytes
- t lymphocytes activate b lymphocytes, which divide into plasma cells
- plasma cells make more antibodies to a specific antigen
