communicable diseases

Question 1

define disease

Answer 1

departure from good health caused by malfunction of the mind/body

Question 2

define communicable disease

Answer 2

caused by infectious agent

Question 3

define parasite

Answer 3

organism tha loves on/within another- causing harm to the host

Question 4

define pathogen

Answer 4

MICROORGANISM that causes disease

Question 5

how do bacteria cause diseases differently to other pathogens

Answer 5

b- produce toxins which damage host tissue

other- damage host tissues directly

Question 6

describe bacteria and how they cause disease

Answer 6

prokaryotic cells
many aren’t pathogens
gram positive- purple- blue under light microscope when stained
gram negative- red under light microscope
secrete toxins that damage cells by breaking down membranes

Question 7

describe viruses and how they cause disease

Answer 7

non-living
have DNA/RNA
intracellular parasites
-invade living cells
-insert own genetic material into hosts DNA
-use host cell to reproduce new viruses rapidly
-burst out of cell, destroying it and spreading to others

Question 8

describe protoctists and how they cause disease

Answer 8

eukaryotic
only few are pathogens
often need vectors to transfer
take over cells and break them open
-digest contents

Question 9

describe fungi and how they cause disease

Answer 9

eukaryotic
can be uni/multicellular
can’t photosynthesise
secrete enzymes to extracellularly digest food and absorb nutrients

Question 10

name an describe a direct method of transmission

Answer 10

physical contact

Question 11

name and describe indirect forms of transmission

Answer 11

droplet infection
-contact with bodily fluids
contact with fomites
-things infected ppl have touched
vectors

Question 12

name and describe plant defences to disease

Answer 12

recognition

• receptors in cells respond to mol.s on pathogens
• signalling mol.s released that with on genes
• triggering cell responses e.g. strengthening walls, producing defensive chemicals

physical defences

• cells next infected one produce high levels of callose
• synthesised and deposits between cell membrane + wall
• prevents pathogen entering
• lignin added to make barter stronger

chemical defenders

• repel insect vectors
• kill invading pathogens

Question 13

describe defences in the skin

Answer 13

dead, out cells full of keratin- difficult to penetrate
dead cells flake off with pathogens
sebum from sweat gland has low pH which inhibits pathogen growth
harmless microorganisms reduce pathogen N due to competition

Question 14

describe defences of the gut wall

Answer 14

saliva has lysozyme which digests bacteria walls

stomach has hydrochloric acid which destroys bacteria

Question 15

describe defences of the urinary tract

Answer 15

mucus traps pathogens
harmless microorganisms
lysozyme in urine

Question 16

describe defences of the gas exchange surface

Answer 16

mucus

cilia sweep the away to mouth to be expelled

Question 17

describe the inflammatory response

Answer 17

tissue damage activates mast cells which secrete histamine and cytokines

Question 18

describe the effects of histamines

Answer 18

dilate blood vessels
-increases blood flow + body temp
increase permeability of blood vessels
-easier for WBCs to leave vessels
-plasma forced out- causing swelling

Question 19

describe the effects of cytokines

Answer 19

attract phagocytes to engulf pathogens

cause hypothalamous to raise body temp (fever)

Question 20

describe the process of blood clotting

Answer 20

platelets become sticky
secrete thombroplastin
activates prothrombin into thombrin
converts fibrinogen (soluble) to fibrin (insoluble)
forms mesh that traps RBCs

Question 21

describe phagocytosis

Answer 21

neutrophils and macrophages
phagocytes recognise non-human proteins
engulf pathogen into phagosomes
phagosome combines with lysosome to form phagolysosome
enzymes from lysosome direct pathogen

Question 22

describe the specific immune response

Answer 22

antigens= protein/ polysaccharide on pathogen surface
antibodies= proteins secreted by b lymphocytes in response to non-self antigens- neutralise pathogens

Question 23

describe the structure of antibodies

Answer 23

hinge region
-provide flexibility so can attach to antigens
variable region
-different primary (and tertiary) structure in different antibodies
-specific to antigens
constant region
-binds to phagocyte receptors

Question 24

describe b cells

Answer 24

mature in bone marrow
produce antibodies with some binding site as receptor
used outside pathogen cells

Question 25

describe t cells

Answer 25

mature in thymus gland
t killer cels
-kill defective body cells
t helper cells
-receptors bind to antigens
- stimulate t and B cell activity

Question 26

describe the humoral response

Answer 26

non-sef antigens displayed by pathogen
macrophage (phagocyte) cells ingest pathogen displaying parts of it on surface
clonal selection= b+T cells with complementary receptors bind ( are selected)
clonal expansion
-t helper cells secrete interleukins
-which stimulate B cells to divide
-mitosis produces many clones of particular B cell
differentiation
-some clones specialise to become plasma cells which fit antigens on pathogen surface
-others become memory cells which form plasma cells of are pathogen enters again

Question 27

what are some variations of the humoral response

Answer 27

B cell ingests pathogen itself
B cell encounters enough antigen to become active without t helper cell
-no helper cells produces

Question 28

name and define some antibody-antigen reactions

Answer 28

neutralisation
-bacteria, toxins and viruses can’t enter cells
opsonisation
-phagocytes have receptors that bind to constant region of antibody
agglutination
-binding 2/more pathogens together
-harder to spread
-phagocytes can ingest >1 pathogen at a time