communicable disease

Question 1

what are the main disease causing pathogens in humans

Answer 1

bacteria and virus

Question 2

what type of pathogen causes TB

Answer 2

bacteria

Question 3

what pathogen causes TB

Answer 3

Mycobacterium tuberculosis

Question 4

what does TB infects

Answer 4

phagocytes in the lungs

Question 5

what does TB lead to

Answer 5

breathing problems, coughing, weight loss, fever and can result in death

Question 6

what are examples of physical defences against pathogens in plants

Answer 6

cellulose cell walls
a lignin layer that thickens the cell wall
waxy cuticles
old vascular tissue is blocked to stop the pathogen spreading

Question 7

what mechanisms are activated in plants when a pathogen is detected

Answer 7

closing of the stomata to prevent entry to the leaves
additional thickening of cell walls
callose deposits between cell wall and cell membrane near the site of infection to strengthen cell wall
necrosis which is when cells near the infection are killed by intracellular enzymes

Question 8

what are the physical barriers against infection in animals

Answer 8

skin consisting of keratin
stomach acid that kills bacteria
gut and skin flora that compete with pathogens for food and space

Question 9

explain inflammation

Answer 9

histamines released by mast cells in the injured tissue cause vasodilation which increases blood flow to the infected area and increases permeability of blood vessel.
antibodies, white blood cells and plasma leak out into the infected area and destroy the pathogen

Question 10

explain lysozyme action

Answer 10

lysozymes are enzymes found in secretions such as tears and mucus that kills bacterial cells by damaging their cell walls

Question 11

what is phagocytosis

Answer 11

a process in which white blood cells engulf pathogens, destroying them by fusing a pathogen enclosed in a phagocytic vacuole with a lysosome

Question 12

explain blood clotting

Answer 12

reduces the blood loss by temporarily sealing the opening thus preventing the entry of pathogens

Question 13

what are memory cells

Answer 13

cells that replicate themselves when exposed to an invading pathogen and remain in the lymph nodes searching for the same antigen thus resulting in a much faster immune response.

Question 14

what are B effector cells

Answer 14

antibody producing cells

Question 15

what are T helper cells

Answer 15

stimulate B cells and T killer cells to divide

Question 16

what are T killer cells

Answer 16

destroy pathogen infected cells

Question 17

explain the humoral response

Answer 17

a B cell is triggered when it encounters its matching antigen
the B cell engulfs the antigen and digest it
it then displays the antigen on its surface
a matching T cell is then attracted
the T cell secretes cytokines which help the B cell multiply and divide into plasma cells
then released into the blood and the antibodies lock onto matching antigens

Question 18

explain the cell mediated response

Answer 18

macrophage ingests the antigens
processes them
presents them to a T helper cell
produces clones to produce a T helper cell, a T killer cell or a memory cell

Question 19

what are antibodies

Answer 19

globular proteins produced by lymphocytes

Question 20

explain antibody action

Answer 20

neutralisation- have a complementary shape to a specific antigen. they attach to the antigen and inhibit its action
agglutination- several antibodies clump the antigens together allowing easier digestion

Question 21

describe the structure of antibodies

Answer 21

composed of four polypeptide chains which are linked by disulfide bridges
have a constant region and a variable region
contain hinge region responsible for flexibility

Question 22

what is meant by active immunity

Answer 22

results from the production of antibodies by the immune system in response to the presence of an antigen

Question 23

what is meant by passive immunity

Answer 23

the introduction of antibodies from another person or animal

Question 24

direct transmission

Answer 24

direct contact (kissing, skin to skin contact)
inoculation (break in skin, animal bite)
ingestion (contaminated food or drink)

Question 25

indirect transmission

Answer 25

fomites (ianimate objects)
droplet infection (mucus and saliva when cough talk or sneeze)
vectors (often but not always animals)

Question 26

blood clotting and wound repair

Answer 26

platelets adhere and secrete substances
thromboplastin (enzyme that triggers cascade of reaction forming blood clot)
serotonin (makes walls of blood vessels contract and narrow to reduce supply of blood in that area)

Question 27

stages of phagocytosis

Answer 27

pathogens produce chemicals to attract phagocytes
engulfs pathogen and encloses in a vacuole known as a phagosome
phagosome combines with lysosome forming a phagolysosome
enzymes digest and destroy the pathogen

Question 28

pharmacogenomics

Answer 28

the science of interweaving knowledge of drug actions with personal genetic material

Question 29

synthetic biology

Answer 29

using populations of bacteria to produce much needed drugs that would otherwise be too rare, expensive or just not available