4.1 - Communicable Diseases - New

Question 1

Pathogen def

Answer 1

A microorganism that causes disease

Question 2

4 different types of pathogen

Answer 2

Bacteria
Fungi
Viris
Protoctista

Question 3

Different bacterial diseases

Answer 3

TB
Bacterial Meningitis
Ring Rot (in plants)

Question 4

Different diseases caused by viruses

Answer 4

HIV/AIDS
Influenza
Tobbaco Mosaic Virus

Question 5

Different fungal diseases

Answer 5

Black Sigatoka
Ringworm (cattle)
Athlete’s foot (humans)

Question 6

Diseases caused by protoctista

Answer 6

Blight (tomatoes and potatoes)

Malaria

Question 7

Direct Transmission def

Answer 7

Passing a pathogen from host to new host, with no intermediary

Question 8

Indirect Transmission

Answer 8

Passing a pathogen from host to new host, via a vector

Question 9

Transmission def

Answer 9

Passing a pthogen from an infected individual, to an uninfected individual

Question 10

Vector def

Answer 10

An organism that carries a pathogen from one host to another

Question 11

Simple pathogen life cycle

Answer 11

Travel from one host to another (transmission)
Enter host tissues
Reproduce in host tissues
Leave the host tissues
Infect a new uninfected person

Question 12

Different means of direct transmission

Answer 12

Direct physical contact
Faecal-oral transmission
Droplet infection
Transmission by spores

Question 13

Methods to decrease transmission by direct physical contact

Answer 13

Direct physical contact

• hygiene - wash hands regularly
• keep surfaces clean - especially door handles
• clean and disinfect cuts and abrasions
• sterilise surgical instruments
• use condoms during sexual intercourse

Question 14

Methods to decrease transmission by faecal-oral transmission

Answer 14

• treatment of waste water and drinking water to decontaminate and reduce risk
• thorough washing of all fresh food (using treated water)
• careful prep and cooking of all food

Question 15

Methods Methods to decrease transmission by droplet infection

Answer 15

Catch it - bin it - kill it
Cover mouth when coughimg or sneezing
Use tissue and dispose of correctly after use

Question 16

Methods to decrease transmission by transmission by spores

Answer 16

Use of a face mask

Washing skin after contact with soil

Question 17

Social factors affecting transmission of diseases

Answer 17

Overcrowding
Poor ventilation
Poor health - especially with HIV/AIDS
Homelessness
Living or working with people who ahve migrated from areas where disease is common

Question 18

Life cycle of Plasmodium and malaria

Answer 18

Person with malaria
Gametes of Plasmodium in blood
Female Anopheles mosquito sucks blood
Plasmodium develops and migrates to mosquito’s salivary glands
Uninfected person is bitten
Plasmodium migrates to liver
Plasmodium migrates to blood

Question 19

What conditions are optimal for many pathogens

Answer 19

Warm, moist conditions

• allows them to reproduce more rapidly
• so greater variety of pathogens may be present in these conditions

Question 20

Callose def

Answer 20

A large polysaccharide deposit that blocks old phloem sieve tubes

Question 21

Plant physical defences, and more info on the,

Answer 21

• Cellulose cell wall - contains many chemical defences that can be activated on detecting pathogen
• Lignin thickening of cell walls - waterproof and almost completely indigestible
• Waxy cuticles - prevent water colection on cell surfaces, prevents pathogens accumulating there, need water to survive
• Bark - contains a variety of chemical defences against pathogens
• Stomatal closure - closed, as are possible points of entry for pathogens - controlled by guard cells when pathigens detected.
• Callose - large polysaccharide deposited in sieve tube at end of growing season.
• blocks flow of assimlates, and pathogens in sieve tube elements
• Tylose Formation - balloon-like swelling or projection that fills the xylem vessel
• plugs vessel, and water (and pathogens) can longer move through the xylem

Question 22

Chemical defences for plants

Answer 22

Terpenoids
Phenols
Alkaloids
Defensive proteins
Hydrolytic enzymes

Question 23

Active defences in plants, and more info

Answer 23

• Cell walls become thickened with additional cellulose
• Deposition of callose between plant cell wall and memebrabe near invading pathogen
• Oxidative bursts - produce highly reactive O2 molecules capable of damaging invading pathogen cells
• Increase in production of chemicals
• Canker - necrotic lesionin woody tissue - causes death of cambium tissue in bark

Question 24

Inflammation def

Answer 24

swelling (odoema) and redness caused by infection

Question 25

what is a mucous membrane?

Answer 25

specialiswd epithelial tissue covered by mucus

Question 26

primary defences def

Answer 26

defences that prevent pahogens entering the body

Question 27

list different primary defences in the human body

Answer 27

skin
blood clotting and skin repair
mucous membranes
coughing and sneezing
inflammation

Other:
enzymes and antibodies in tear fluid
ear canal lined by wax - traps pathogens
mucus plug in cervix, relatively acidic conditions in vagina

Question 28

what are the primary “non-specific” defences

Answer 28

defences that prevent pathogens entering the body and bloodstream, but are not specific to any one pathogen or antigen - prevent entry of any pathogen

Question 29

how does skin act as primary defence

Answer 29

skin conists of layers of cells
outer layer called epidermis
acts as a barrier for pathogens

Question 30

Outline the process of blood clotting and skin repair

Answer 30

Blood Clotting

platelets bind to exposed collagen
they release clotting factors
this activates an enzyme cascade
this causes fibrinogens to form insoluble fibres that attach to the platelets in the plug
red blood cells and platelets are trapped in place
this forms a blood clot

Skin Repair

when clot has formed
dries out and forms a scab
as it dries, it draws sides of the cut together
makes temp. seal under which skin is repaired
fibrous collagen deposited under scab
stem cells in epidermis divide by mitosis to form new skin cells
they migrate to edge of cut - diff. to form new skin
new blood vessels grow to supply O2 and nutrients to new cells
edge of cut contracts and skin is repaired - scab falls off

Question 31

how does mucous membrane act as primary defence

Answer 31

thin layers in body, e.g. alveoli, lungs, blood vessels etc., contain mucous membranes
mucus secreted by goblet cells
mucus traps any pathogens
epithelium also contains ciliated cells
cilia can move to waft the mucus with pathogens along and out of airways
enter oesophagus and is swallowed
killed by stomach acid

Question 32

how coughing and sneezing acts as primary defence

Answer 32

expulsive reflex

expels any pathogens in airway that caused the irritation

Question 33

inflammation mechanism

Answer 33

pathogen detected by mast cells
this causes release of histamines
causes vasodilation
makes capillary walls more permeable to white blood cells
plasma and WBC leave blood vessel and enter tissue fluid
causes increased prod. of tissue fluid
causes swelling (odoema)
excess tissue fluid drained into lymphatic system - where lymphocytes are stored
can lead to pathogens coming into contact with lymphocytes
causes initiation of primary immune response

Question 34

what is an antigen presenting cell (APC)?

Answer 34

a cell (usually phagocyte) that incorporates the antigens of a pathogen into its cell surface membrane so it can be recognised by other cells in immune system

Question 35

clonal selection def

Answer 35

selection of a specific B or T cell specific to the antigen

Question 36

what are cytokines?

Answer 36

hormone-like molecules used in cell signalling to stimulate the immune response

Question 37

what are neutrophils?

Answer 37

a type of white blood cell that engulfs foreign matter and traps it in a large vacuole (phagosome),
which fuses with lysosomes to digest the foreign matter.
- a type of phagocyte

Question 38

what are opsonins?

Answer 38

proteins that bind to the antigen on a pathogen and then allow phagocytes to b

Question 39

parasite def

Answer 39

an organism that:

• lives in/on host
• gains nutrition from host
• at expense of host