Communicable Diseases

Question 1

name 4 types of pathogen that can cause communicable diseases

Answer 1

bacteria
fungi
protoctista
viruses

Question 2

how does myobacterium tuberculosis cause disease

Answer 2

triggers inflammatory response by infecting phagocytes in lungs
infected phagocytes sealed in waxy coated tubercles so bacteria remain dormant
first infection has no symptoms
if another factor weakens immune system, bacteria becomes active and destroys lung tissue

Question 3

how does HIV result in symptoms of AIDS

Answer 3

attachment proteins bind to complementary CD4 receptors on Th cells
HIV replicates inside Th cells killing or damaging them
AIDS develops when there were too few Th cells for immune system to function
individuals cannot destroy other pathogens and suffer from secondary diseases

Question 4

how does tobacco mosaic virus cause disease

Answer 4

affects plants and transmitted via sap
contains ssRA which is directly transcribed by host cell to assemble new virions
virions enter cells via plasmodesmata then enter xylem and phloem
causes stunted growth

Question 5

how does the influenza virus cause disease

Answer 5

transmitted via droplet infection
injects viral RNA into ciliated epithelial cells of throat and lungs
viral RNA hijacks cell biochemistry to produce new virions
cell lysis releases virions

Question 6

what causes malaria

Answer 6

female mosquito acts as vector when it transfers saliva to another organism during feeding
parasite reproduces asexually in red blood cells causing lysis

Question 7

what causes potato blight

Answer 7

protoctista behaves similarly to a fungus
mainly transmitted via spores

Question 8

what causes ring rot

Answer 8

bacteria mainly transmitted by planting infecting seeds

Question 9

describe 3 fungal infections

Answer 9

sac fungus causes leaf spot disease black Sigatoka in banana plants
ringworm transmitted through direct contact
athletes foot

Question 10

how are communicable pathogens transmitted directly

Answer 10

inhalation
skin to skin contact or exchange of fluids
penetrate skin actively using enzymes or passively

Question 11

how are communicable pathogens transmitted indirectly

Answer 11

consumption of contaminated foods
via a vector
spores

Question 12

how do living conditions affect transmission

Answer 12

overcrowding increases direct transmission
climate determines which organisms can survive
social factors determine how quickly people are treated

Question 13

name 4 physical barriers to pathogen entry in plants

Answer 13

cellulose cell walls
lignified layer
waxy upper cuticle
old vascular tissue blocked to prevent pathogens from spreading inside plant

Question 14

describe 2 mechanical responses to infection in plants

Answer 14

guard cells close stomata
thick polysaccharide callose is produced and deposited between cell wall and plasma membrane to increase entry distance

Question 15

what is necrosis

Answer 15

injury activates intracellular enzymes in plants that kill cells near the site of infection to prevent pathogen from spreading

Question 16

describe the chemical defences plant use

Answer 16

terpenoids-act as antibacterials
phenols-interfere with digestion
alkaloids-provide bad tastes
defensins- inhibit transport channels hydrolytic enzymes-break down cell wall of invading organism

Question 17

name 5 barriers to infection in animals

Answer 17

skin is tough keratin layer
blood clotting prevents pathogens entering through skin lesions
hydrochloric acid in stomach kills bacteria
harmless bacteria increase interspecific competition with pathogens
mucous membranes trap pathogen

Question 18

what are expulsive reflexes

Answer 18

body attempts to force foreign substances out

Question 19

outline the process of inflammation

Answer 19

damaged vessels release histamines causing vasodilation
blood flow and permeability of blood vessels increases
white blood cells and plasma move into infected cells

Question 20

how does blood clotting occur

Answer 20

blood platelets form plug and release chemicals that enhance clotting prothombin changes into thrombin-its active form
fibrinogen changes into insoluble fibres which covers wound

Question 21

how does phagocytosis destroy pathogens

Answer 21

phagocyte moves towards pathogen which may have been marked by opsonins
phagocyte engulfs pathogen via endocytosis to form a phagosome
phagosome fuses with lysosome (phagolysosome)
lysozomes digest pathogens
phagocyte absorbs the products from pathogen hydrolysis

Question 22

explain the role of antigen presenting cells

Answer 22

macrophage displays antigen from pathogen on its surface
enhances recognition by Th cells which cannot directly interfere with pathogens
secrete cytokines involved in stimulating specific immune response

Question 23

what are lysozymes

Answer 23

digestive enzymes
found in lysosomes and secretions
damage bacterial cell walls causing osmotic lysis

Question 24

name the two types of specific immune system

Answer 24

cell mediated
humoral

Question 25

outline the process of cell mediated response

Answer 25

complementary Th lymphocytes bind to foreign antigens on APC cell signalling via secretion of interleukins stimulates -clonal expansion of Th cells: become memory cells or trigger humoral responses -clonal expansion of cytotoxic T cells: secrete perforin to destroy infected cells

Question 26

outline the process of humoral response

Answer 26

complementary Th lymphocyte bind to foreign antigens on antigen presenting T cells release cytokines that stimulate cell expansion of complementary B lymphocytes B cells differentiate into plasma cells plasma cells secrete antibodies with complementary variable region to antigen

Question 27

describe the structure and function of B and T lymphocytes

Answer 27

many specific receptors and immunoglobulins on surface B cells differentiate into plasma cells to secrete antibodies

Question 28

what are the three types of T cells and their function

Answer 28

T helper cells-secrete cytokines T killer cells-secrete perforin T regulator cells-suppress other immune cells to prevent autoimmune disease

Question 29

what is an antibody

Answer 29

protein secreted by plasma cells

Question 30

describe the structure of an antibody

Answer 30

quaternary structure: two light chains held by disulfide bridges and 2 longer heavy chains binding sites on variable regions of light chains have specific tertiary structure complementary to an antigen

Question 31

how do antibodies lead to the destruction of a pathogen

Answer 31

agglutinins form antigen-antibody complexes to enhance phagocytosis opsonins mark microbes for phagocytes antitoxins make toxins insoluble via precipitation

Question 32

what are memory cells

Answer 32

specialised T/B cells produced from primary immune response remain in low levels in the blood can divide rapidly by mitosis if an organism encounters the same pathogen again

Question 33

contrast the primary and secondary immune response

Answer 33

secondary reponse: faster rate of antibody production higher antibody concentration antibody levels remain higher pathogen usually destroyed before symptoms

Question 34

compare and contrast active and passive immunity

Answer 34

both involve antibodies active: memory cells=long term time lag lymphocytes produce antibodies needs direct contact with antigen passive: no memory cells=long term immediate antibodies from external source no direct contact with antigen

Question 35

give examples of passive immunity

Answer 35

passive natural=antibodies in breast milk passive artificial=needle stick injections

Question 36

give examples of active immunity

Answer 36

active natural=humoral response active artificial=vaccinations

Question 37

define autoimmune disease

Answer 37

immune system produces antibodies against own tissue example=lupus results in inflammation throughout the body

Question 38

explain the principles of vaccination

Answer 38

vaccine contains dead/ inactive form of pathogen triggers primary immune response memory cells produced and remain in the bloodstream so secondary response is rapid and produces high concentrations of antibodies pathogen in secondary response is destroyed without symptoms

Question 39

define endemic

Answer 39

disease occurs routinely in a geographical area

Question 40

define epidemic

Answer 40

temporary rapid increase in incidence of a disease in a geographical area

Question 41

what role do vaccines play in preventing epidemics

Answer 41

routine vaccination reduces available carriers of pathogen resulting in herd immunity vaccinating close contacts of infected individuals limits spread of pathogen

Question 42

list some possible natural sources of medicines

Answer 42

fungi (penicillin) plants

Question 43

what is personalised medicine

Answer 43

genome sequencing has enabled scientists to predict an individuals response to disease/medicines so prescriptions targeted

Question 44

what is synthetic biology

Answer 44

engineering that targets biochemical processes

Question 45

what are the benefits of using antibiotics

Answer 45

effectively reduce population of bacterial colony bacteriostatic antibiotics-prevent protein synthesis bactericidal antibiotics-prevent formation of peptidoglycan cross links in cell walls

Question 46

what are the risks of using antibiotics

Answer 46

overuse increases selection pressure for resistant strains antibiotic resistant infections are difficult to treat