biology C3.2

sl

major causes od disease

genetic factors

environmental factors

infectious agents

define pathogen

microorgansims that causes disease

major pathogen types

viruses

bacteria

fungi

worms

define primary defense

physical and chemical barriers that prevent pathogen entry

role of skin in primary defense

physical barriers; keratin blocks entry

sebaceous glands in primary defense

secrete oils and acids that inhibit microbes

mucous membranes in primary defense

trap pathogens; contain lysozyme and cilia

benefits of blood clotting

prevents blood loss; prevents pathogen entry

roles of platelets

release clotting factors; form a temporary plug

blood clotting cascade

1. Platelets activate.

2. Clotting factors convert prothrombin → thrombin.

3. Thrombin converts fibrinogen → fibrin.

4. Fibrin forms mesh stabilizing clot.

innate immunity

fast, non-specific, uses phagocytes

adaptive immunity

slow, specific, uses lymphocytes, memory

function of phagocytic WBCs?

enguld and destory pathogens

how does a macrophage destory a pathogen

Recognizes → engulfs → forms phagosome → fuses with lysosome → digests → exocytosis of waste.

structure and function of lymphocutes

large nucleus; produce specific immune responses

where are lymphocytes found?

blood, lymph nodes, spleen

define specific immune response

targets one particular antigen

define antibody

protein that binds specifically to antigens

role of lymphocytes

produce antibodies against specific pathogens

define antigen

molecule that triggers an immune response

strcture of antigen

proteins or polysaccharides on pathogen surfaces

what happens when antibody binds antigen?

neutralisation or marking for phagocytosis

differences in blood antigens?

types differ in surface carbohydrate antigens

consequnces of mismatched transfusion

Agglutination → hemolysis → circulation blockage

activation of helper T cells

macrophage presents antigen —> helper T binds —> activates

role of helper T cells in B activation

Release cytokines that activate specific B cells.

what activates B-cells?

binding to antigen and activation by helper T-cell

describe clonal selection

activated B cells divide to form clones of plasma cells

what do plasma B-cells do?

produce large quantities of antibodies after differentiating

define immunity

ability to resist disease due to memroy cells

role of memory B cells

respond rapidly on re-exposure

primary response

slow, small, short-lasting

secondary response

fast, large, long-lasting

how is HIV transmitted

blood, semen, vaginal fluids, breast milk, shared needles

consequence of HIV

infects and destory helper T cells —> weakens immunity

relationship between HIV and AIDS

AIDS is advanced HIV wirh severe immune deficiency

natural function of antibiotics in fungi

kill competing bacteria

function in medicine

block bacterial matabolic processes

why ineffective against viruses

viruses lack metabolism and cell strctures targeted by antibiotics

how does natural selection cause ressitance?

mutations —> resistance bacteria survive antibiotics —> spread

major routes of pathogen transmission

air, water, bodilty fluids, vectors, food, contact

why are most pathogens species-specific

require specific cell receptors

define zoonosis

disease that transfers from animals to humans

example of zoonotic pathogen

rabies cirus

SARS

ebola

reasons zoonoses increase

habitat loss, wildlife trade, farming density, climate change

define immunisation

deliberate exposure to antigen to provoke immunity

vaccine ingredient classes

inactivated pathogens

subunit antigens

mRNA

principle of vvaccination

stimulates primary response —> creates memory —> faster secondary response

define herd immunity

protection of a population when enough individuals are immune

how does it limit disease

interrupts transmission chain

define R0

average number of people one infected person infects

how to estimate immunity needed for herd immunity

threshold = 1 - 1/R0