IB biology: topic 6: responses to disease

what are the primary levels of defence? (8)

ears,

nose,

eyes,

blood clotting,

digestive system,

respiratory tract,

skin,

vagina

how do the eyes protect against infection?

tears contain lysozyme

how do the ears protect against infection?

wax + hairs

how does the nose protect against infection?

mucus + hairs

how does blood clotting protect against infection?

semi-solid gel seals up wound to prevent entry of pathogens.

how does the digestive system protect against infection?

acidic conditions produced by stomach acid

how does the respiratory tract protect against infection?

cilia + mucus

how does the vagina protect against infection?

has mucus

how does the skin protect against infection?

secretes sebum (oil)

what are characteristics of the skin?

tough outermost layer,

physical barrier to pathogens,

protects against physical and chemical damage,

what does the skin produce in order to fight infection?

sebum (oil) - maintains skin moisture and slightly lowers pH to inhibit bacterial and fungal growth.

where are mucous membranes found?

the respiratory tract, digestive system & genitals

what allows mucous membranes to fight against infection?

produces mucus which is a sticky solution of glycoproteins

that traps pathogens and harmful particles which are then

swallowed or expelled.

has antiseptic properties due to the antibacterial lysozyme

what are characteristics of mucous membranes?

acts as a physical barrier,

thinner and softer

describe the process of producing fibrin

thrombin promotes the production of fibrinogen, which in turn promotes the production of fibrin, which is used to repair damaged blood vessel walls.

describe the process repairing a damaged blood vessel wall

when a blood vessel wall is damaged, platelets aggregate at the site forming a temporary plug.

clotting factors are then released to produce fibrin

why must blood clotting be under strict control?

as if it occurs inside blood vessels the clots can cause blockages.

what is the next line of defence if primary defences are breached?

white blood cells

how do phagocytes work to fight infection?

squeeze through fenestrations to sites of infection,

engulf pathogens by endocytosis and digest them with lysosomal enzymes.

phagocytes: specific or non-specific?

non-specific

how do lymphocytes work to fight infection?

each will respond to only one particular foreign antigen on surface of pathogens.

produce antibodies specific to antigen.

lymphocytes: specific or non-specific?

specific.

how many lymphocytes are present in the immune system?

a small number of all required - too few lymphocytes to produce enough antibodies to control a pathogen.

Antigens stimulate lymphocytes to divide and form a large clone of antibody-producing plasma cells.

what are antibodies?

large proteins that can prevent virsues docking onto host cells and can activate complement pathway which leads to pathogen being lysed.

also can make pathogen more recognisable to phagocytes.

what is the structure of an antibody?

light variable (lv), light constant (lc)

heavy variable (hv), heavy constant (hc),

how does the structure of an antibody allow it do to its job?

constant region helps body neutralise pathogen.

hypervariable region binds to specific antigen.

how long do antibodies persist for?

only for a few weeks or months.

what can lymphocytes turn into during response?

plasma cells (gradually lost) or memory cells (long-lived)

what are memory cells?

long-lived cells that remain inactive until re-infection when they divide rapidly to produce plasma cells.

what is immunity?

possessing the antibodies and/or the memory cells for an infectious disease.

what does HIV stand for?

Human Immunodeficiency Virus

what type of virus is HIV? what does this mean?

retrovirus - reverse transcriptase so causes host cell to produce its own DNA copies

how does AIDS spread?

by blood:

sexual intercourse (bleeding can occur), blood transfusions, sharing of hypodermic needles

what cells does HIV attack?

helper T cells

what does AIDS stand for?

acquired immunodeficiency syndrome

how is AIDS different from HIV?

once a collection of several diseases/conditions exist together, due to HIV being present

how do antibiotics work?

block processes (DNA replication, transcription, translation, ribosome function and cell wall formation.)

that occur in prokaryotes but not eukaryotes so kill bacteria without harming human cells.

what are antibiotics?

chemicals that inhibit growth of microorganisms.

why can’t antibiotics be used to treat viruses?

viruses are non-living and therefore do not possess a metabolism.

what are the risks of using antibiotics to treat viruses?

contributes to overuse of antibiotics and emergence of antibiotic resistance.

can viral diseases be treated with antibiotics?

no

how does antibiotic resistance develop?

bacteria mutate so that genes have resistance to antibiotics.

what are ways that we can reduce antibiotic resistance?

doctors only prescribe antibiotics for serious bacterial infections.

patients complete courses to ensure infection is entirely eliminated.

hospital staff must maintain high standards of hygiene

farmers not add antibiotics to animal feed to promote growth.

pharmaceutical companies need to develop new types of antibiotic

describe the functioning of immunoglobulin

• antibodies

• variable sites for binding

• specific to antigens on bacteria

• constant region marks pathogen

• attract phagocytes