C12- Communicable disease

Question 1

Communicable disease

define

Answer 1

A disease that can be passed from one organism to another

Question 2

Pathogen

Define

Answer 2

A microorganism that causes disease

Question 3

Bacteria

General

Answer 3

prokaryotes

no membrane bound organelles

produce toxins

Question 4

Bacteria

Gram staining technique

Answer 4

due to two types of bacterial cell walls

gram positive- purple blue

gram negative- red

Question 5

Virus

general

Answer 5

Non living

invade living cells, use viral DNA to tell cell to reproduce virus, then burst cell

can lie dormant

not cells- no nucleus and cannot reproduce on its own

Question 6

Fungi

general

Answer 6

eukaryotic cells

digest food extracellularly

send threads (hyphae) into organisms

reproduce sexually or asexually

Question 7

General strategy of a pathogen

Answer 7

damage tissues of host organism directly

produce toxins which damage tissues

Question 8

Ways that pathogens damage tissue directly

Answer 8

Virsues take over cell metabolism and genetic material of a cell

break cells open as new generation of pathogen emerge

fungi digest and destroy living cells

Question 9

effect of pathogens produce toxins

Answer 9

fungi produce toxins that effect the host cell and cause disease

bacteria produce toxins that damage host cells

Question 10

Plant disease

TMV

Answer 10

virus that infects a range of over 150 plant types

damages leave sand flowers

stunts growth

resistant crop strains available

Question 11

Plant disease

potato blight

Answer 11

Fungus

hyphae penetrate host cells

resistant strains and careful management

Question 12

Plant disease

black sigatoka

Answer 12

banana fungus

attacks and destroys leaves

hyphae penetrate leaf cells and turn them black

use resistant strains and fungicides

Question 13

Plant disease

Ring rot

Answer 13

bacterial disease (gram positive)

damages leaves and tubers

field cannot be used for 2 years after infection

Question 14

Methods of direct transmission- animals

3

Answer 14

Direct contact

inoculation

Ingestion

Question 15

What is innoculation

Answer 15

Introduction of pathogenic microorganisms, infective material or other substances into tissues of living organism or culture media

Break in the skin- e.g. wound or bite

Question 16

Indirect transmission- animals

3

Answer 16

Fomites

Droplet infection (inhalation)

Vectors

Question 17

What are fomites

Answer 17

Inanimate objects such as bedding, socks or cosmetics that can transfer pathogens

Question 18

Factors affecting rate of transmission of disease in animals

5

Answer 18

overcrowded conditions

poor nutrition

compromised immune system

Poor waste disposal

Culture and infrastructure

Question 19

Direct transmission- plants

Answer 19

Direct contact of a healthy plant with an infected plant

Question 20

Indirect transmission- plants

Answer 20

Soil contamination

leaves pathogens in the soil to infect plants

Question 21

Vectors- plant disease

4

Answer 21

wind- carries spores

water

animals

humans

Question 22

Factors affecting the rate of transmission of communicable disease in plants

5

Answer 22

Crops that are susceptible to disease

overcrowding

Poor mineral nutrition

damp warm conditions

climate change

Question 23

Why do viruses not use erythrocytes as host cells

Answer 23

No nucleus

Needs host cell DNA to replicate

Question 24

Why does the malarial pathogen plasmodium spend part of its life cycle inside eryrocytes

Answer 24

To hide from the immune system

Source of food for growth

Question 25

Key non specific defences animals 6

Answer 25

Tears - Contain lysozymes which break down bacteria and fungal cell walls Skin – prevents entry and has good bacteria which out-compete pathogens Mucous membranes traps microbes and contains lysozymes and phagocytes Saliva contains enzymes and antimicrobial chemicals Stomach acid– Low pH kills pathogens

Question 26

Process of blood clotting 6 key steps

Answer 26

Damage to blood vessel exposes collagen, activating platelets Platelets bind to the exposed collagen releasing clotting factors and forming tendrils, form a platelet plug A clotting factor is thromboplastin, which catalyses the conversion of prothrombin to thrombin in presence of Ca+ Thrombin catalyses the reaction that converts fibrinogen into fibrin Fibrin is an insoluble protein, made of mesh fibres, which then attach to the platelet plug RBCs and other platelets become trapped in the mesh forming a clot

Question 27

Enzymes involved in blood clotting and their process of production

Answer 27

Thromboplastin (clotting factors) +Ca ions prothrombin Thrombin Fibrinogen Fibrin

Question 28

Fibrinogen vs fibrin

Answer 28

Fibrinogen is insoluble Fibrin is insoluble meaning it can form the mesh of fibres needed to form a blood clot

Question 29

Why do platelets produce serotonin

Answer 29

To induce vasoconstriction to limit blood flow to area of rupture

Question 30

Inflammation response Cause and effect

Answer 30

Caused by affected cells producing: Histamines and cytokines Inflammation results in heat, pain, swelling, loss of function and redness

Question 31

What are histamines role in inflammation 3

Answer 31

Causes blood vessels to dilate so increases blood supply This will increase the temperature and thus make the conditions unfavourable for pathogens Causes the vessels to become more permeable. This will cause plasma to leak and a build up of tissue fluid (swelling / oedema)

Question 32

What type of cells produce histamines and cytokines

Answer 32

Mast cells

Question 33

What are cytokines role in inflammation

Answer 33

Small proteins released by cells – cell signalling They message the rest of the body to indicate infection Signal phagocytes to visit site Also message the hypothalamus (controls homeostasis) which causes fever. Microorganisms don’t like it too hot also the specific immune system works more efficiently at higher temperatures

Question 34

Phagocytosis triggers

Answer 34

initiated by cell signalling: Cytokines message the phagocytes Opsonins are attached to the invading pathogen to indicate its presence to the phagocyte Opsonins are (generally) antibodies that 'mark’ a cell (pathogens or self cells) for destruction

Question 35

What are opsonins

Answer 35

Opsonins are attached to the invading pathogen to indicate its presence to the phagocyte Opsonins are (generally) antibodies that 'mark’ a cell (pathogens or self cells) for destruction placed by mast cells

Question 36

Process of phagocytosis

Answer 36

Pathogens produce chemicals that attract phagocytes Phagocytes detect opsonins and antigens- thus identifies the cell as non self and binds to it Phagocyte engulf the pathogen to form the phagosome meanwhile the lyosome moves towards the phagosome fuse to form phagolyosome- digestive enzymes then begin to break down the pathogen The digested pathogen is then absorbed by the phagocyte

Question 37

Which type of cells carry out phagocytosis

Answer 37

Neutrophils and macrophages

Question 38

Differences in phagocytosis with neutrophils and macrophages

Answer 38

On macrophages only the cell becomes an antigen presenting cell (APC) MHC antigen complex is displayed on the membrane

Question 39

What is MHC

Answer 39

A set of genes that code for proteins found on the surface of cells Primarily involved in antigen presentation to T cells, a key process in the immune system

Question 40

What is a lyosome

Answer 40

Specialised vesicle that carries digestive enzymes

Question 41

Characteristics of a neutrophil

Answer 41

Lobed nucleus- to allow it to move to sites of infection through tissue Granulated- due to increased number of lyosomes for phagocytosis