Infection and response

What is the difference between communicable and non communicable diseases

• communicable: infectious diseases spread between organisms through a pathogen

• non communicable: chronic diseases that cannot be spread between organisms, not through a pathogen

What are the main bacterial diseases and their characteristics

• tuberculosis: kills cells, mainly affecting lungs

• meningitis: swells the meninges surrounding brain and spinal cord

• ring rot: decay in vascular tissue of potato tuber or tomato, wilts leaves

What are the main viral diseases and their characteristics

• HIV/AIDS: attacks cells in immune system - antiretroviral drugs

• influenza: attacks respiratory system causing muscle pain and headaches

• TMV: mottles and discolours leaves

What are the main fungal diseases and their characteristics

• black sigatoka: causes leaf spots on bananas

• ringworm: growth of fungus in skin with spore cases erupting, causing rash

• athletes foot: growth under skin of feet between toes

What is direct and indirect transmission

• direct: immediate transfer of pathogens through physical contact

• indirect: transfer of a pathogen through a vector or medium

How are pathogens directly transferred in animals

• touching

• biting

• sexual contact

How are pathogens transferred directly in plants

• entering wounds

How are pathogens indirectly in animals

• airborne droplets

• contaminated surfaces

• ingestion of infected food/water

• vectors - mosquitoes

How are pathogens indirectly transmitted in plants

• wind

• water

• soil

• vectors - aphids

What factors affect transmission

• overcrowding

• poor ventilation

• poor health/diet

• working/living with those who have migrated from areas where disease is common

What are ways to reduce chances of transmission

• vaccinations

• needle exchange programmes

• washing hands frequently

What are physical defences plant have to prevent entry of disease and how do they work

• waxy cuticle - waterproof

• bark - protective outer layer

• cellulose cell walls - form rigid barrier

• thorns/spikes - deter herbivores

• trichromes - trap pathogens

• stomatal closure

• callose - blocks plasmodesmata

What are chemical defences plants have and how do they work

• alkaloids - disrupt metabolic reactions

• phenols & terpenoids - antibacterial and antifungal properties

• hydrolytic enzymes - chitinase breaks chitin in fungal cell walls

• defensins - disrupt pathogen membranes

What is the name of the organism that causes malaria

• plasmodium

What is a parasite

• an organism that lives inside another organism (host) from which it obtains nutrients which causes harm to host cells

Explain how a person is likely to acquire malaria

• person gets bit by a pregnant female mosquito

• parasite is injected into the bloodstream via saliva

• parasite grows in liver cells

State ways HIV is transmitted

• exchange of bodily fluids

• shared needles

• blood to wound

• breastfeeding

• blood transfusion

What are the two types of human defence mechanisms

• specific

• non-specific

What does the specific defence do

• creates antibodies which are specific to antigens

• different responses for each type of pathogen

What does the non-specific defence do

• first line of response including physical barriers

• protects against multiple types of pathogens through phagocytosis which occurs in tissue fluid

What are the two types of specific defences

• cell mediated response

• humoral response (antibody production)

What are the primary defences and what do they do

• skin - prevents entry of microorganisms

• mucus - traps dust, pathogens

• blood clotting - platelets cause scab to form which acts as temporary barrier

• cough&sneeze - removes mucus out of body

• inflammation - causes vasodilation so capillary walls are permeable to WBCs

• tear fluid - contains lysosymes which hydrolyse bacterial cell walls

What are antigens

• (glyco)proteins which are attached to the surface of a pathogen

• stimulates the immune response

What are secondary defences

• phagocytosis (NS)

• antibody production (S)

What are phagocytes and examples

• specialised cells in blood and tissue fluid which engulf and breakdown pathogens

  • neutrophils

  • macrophages

What are types of macrophages

• lymphocytes

• monocytes

What are the key features of neutrophils

• multi-lobed nuclei

• engulf and digest pathogens

• short lived

• released in large numbers

• travel in blood and sometimes tissue fluid

What are key features of macrophages

• oval/kidney shaped nucleus

• larger than neutrophils

• produces antigen-presenting cells

• initiate specific responses to invading pathogens

Explain how pathogens are destroyed by phagocytosis

• phagocyte is attracted to pathogen and recognises the antigen on surface

• phagocyte engulfs pathogen

• pathogen is enclosed in vesicle - a phagosome

• lysosome fuses with phagosome which contains lysosymes/lytic enzymes

• pathogen is digested/destroyed

How can a macrophage act as an antigen-presenting cell

• antigen is removed from pathogens surface

• macrophage sticks antigens onto its own surface

• antigen is exposed so T lymphocytes can recognise it and become activated

• the activated T cells initiate specific immune response

What takes place in active immunity

• antigen presentation

• specific immune response

What is the purpose of the specific immune response

• produced antibodies

• produces memory cells which provide immunological memory

• provides long-term protection from disease

What are the roles of T helper cells and what chemicals do they use

• produce interleukins (cytokine)

• stimulate B cells and antibody production

• attracts other cells and antibodies

What are the roles of T killer cells

• kill pathogens by producing perforin

• makes holes in pathogens plasma membranes

What are the roles of T memory cells

• remain in blood to provide immunological memory

• when second infection occurs, they divide rapidly to form Tk cells

What are the roles of T regulator cells

• prevent an autoimmune response

• represses immune system after all pathogens are destroyed

What is a plasma cell and its role

• B lymphocyte that produces antibodies specific to invading antigen

What is the role of B memory cells

• provide immunological memory

What are the stages of the specific immune response

• infection & reproduction of pathogen

• presentation of antigens

• clonal selection

• proliferation

• differentiation

• action

Outline what happens in the specific immune response

• pathogen enters the body by passing primary defences

• antigen removed from pathogen and moved onto surface of macrophage (APC) allowing immune system to recognise

• antigen on pathogens are detected by T and B cells that carry specific receptor molecules on their plasma membrane

• T/B cell becomes activated when binded to an antigen, they increase in number by mitosis

• B and T lymphocyte clones develop into a range of useful cells

• each of the T and B cells produced have a different action within immune response

What is the difference between cell mediated and humoural response

• cell mediated: activated T lymphocytes undergo clonal selection and differentiate into T killer cells which destroy infected body cells and T memory cells which provide a faster secondary response

• humoural: activated B lymphocytes undergo clonal selection and differentiate into plasma cells which secrete specific antibodies and B memory cells which enable faster secondary response

What is an antibody

• Y-shaped protein produced by plasma cells

• has specific shape with a region that’s complimentary to antigen

What is the structure of an antibody

• variable region: containing antigen binding site which is complimentary to antigen

• constant region: stem which allows binding to receptors on immune system cells - phagocytes

• hinge region: allows flexibility when antibody binds to antigen

• 2 heavy and 2 light polypeptide chains

• constant region has same 1° as they all have same function but variable region has different 1°, 2°, and 3° as they are specific to different antigens

What are the 3 ways that antibodies act on antigens

• agglutination

• opsonisation

• neutralisation