4.1.1

Question 1

Name 4 groups of pathogen that can cause communicable diseases

Answer 1

Bacteria
Fungi
Protoctista
Viruses

Question 2

How does mycobacterium tuberculosis cause disease

Answer 2

Triggers inflammatory response by infecting phagocytes in lungs
Bacteria becomes active and destroy lung tissue

Question 3

What does ring rot do

Answer 3

Affects potatoes and aubergines and damages leaves and fruits
Bacterial disease

Question 4

What causes bacterial meningitis

Answer 4

Often menigococcal bacteria A B C W X Y
Damages membrane around brain
Transmitted by droplet infection and direct contact with saliva

Question 5

How are bacteria’s classified

Answer 5

Basic shapes-rod,spherical, spiralled, corkscrew, comma
Cell walls via gram staining
Positive=purple/blue
Negative= red

Question 6

Describe three viruses

Answer 6

Tobacco mosaic virus- transmitted via infected sap, damages leaves, flowers+ fruits, affects tomato and cucumbers , causes stunted growth
HIV - attachment protein binds to complementary CD4 receptor on Th cells, destroys immune system
Influenza - transmitted via droplet infection,contact with mucus containing, injects viral RNA into CEC- destroys

Question 7

Define three bacterial diseases

Answer 7

Tuberculosis
Meningitis
Ring rot - affects potatoes and aubergines + damages leaves and fruit

Question 8

Describe 3 fungal infections

Answer 8

Black Sigatoka -affect bananas, attack leaves
Ringworm-causes grey, white, crusty circular patches
Athletes foot- in human causes cracking and scaling

Question 9

What are Protoctists and explain blight

Answer 9

Eukaryotic cell
Causes malaria,potato/tomato late blight
Blight -transmitted via spores and causes cell death in leaves

Question 10

What causes malaria

Answer 10

Mosquitoes act as vector for plasmodium spp

Parasite reproduce asexually in red blood cells in liver, causing lysis

Question 11

How are communicable pathogens transmitted directly

Answer 11

Inhalation
Skin to skin or exchange of fluids
Penetrate skin

Question 12

How are communicable pathogens transmitted indirectly

Answer 12

Consumption of contaminated food
Via a vector
Spores

Question 13

Name 4 physical barriers to pathogens entry in plants

Answer 13

Cellulose cell walls
Waxy cuticle
Lignified layer
Old vascular tissue blocked to prevent pathogens from spreading in plant

Question 14

Describe two mechanical and one chemical response to infection in plant

Answer 14

Guard cells close stomata
Polysaccharide cal lose deposited between plant cell walls and plasma membrane to limit spread
Produce anti microbial chemicals

Question 15

What are the primary non specific defences that KEEP PATHOGENS out

Answer 15

Skin -physical barrier of keratin layer
Mucous membrane - trap pathogens and May secrete anti microbial enzymes
Hydrochloric acid
Harmless bacteria in gut and skin to increase interspace competition with pathogens

Question 16

What are secondary defences that help get rid of pathogens

Answer 16

Blood clotting
Inflammation
Expulsive reflexes

Question 17

What happens in blood clotting

Answer 17

Blood clot rapidly seal wound
Thromboplastin -enzyme that triggers lots of reaction resulting in formation
Serotonin -smooth muscle in the walls of the blood vessels contract, reduces supply of blood to area

Question 18

What occurs in inflammation

Answer 18

Can be triggered by tissue damage

Damaged tissue activate mast cells which release histamines and cytokines

Question 19

What are expulsive reflexes

Answer 19

Force foreign substance out
Irritation causes sneezes in mucous membrane
Irritation of ciliated epithelium in respiratory tract causes coughing

Question 20

Outline the process of inflamation

Answer 20

Damages vessels leads to release of histamines causing vasodilation
Blood flow and permeability of blood vessel increases
White blood cell and plasma move into the infected tissue

Question 21

How does phagocytes destroy pathogens

Answer 21

Pathogens produce chemicals that attract phagocytes
Phagocytes engulf pathogen via endocytosis to form a phagosome
Lysozyme digest and destroy pathogens

Question 22

What is an antibody? Describe its structure

Answer 22

Proteins secreted by plasma cells
Quaternary structure
2 long identical polypeptide chains -heavy
2 shorter identical polypeptide chains-light
Held by disulfide bridges
Binding site on variable region Specific tertiary structure complementary to antigen

Question 23

How do antibodies lead to the destruction of a pathogen

Answer 23

Neutralise toxins so they became insoluble
Act as agglutinins so pathogen clump together
Opsonises for phagocytes

Question 24

Name two types of specific immune response

Answer 24

Cell mediated

Hum-oral

Question 25

Outline the process of cell mediated response

Answer 25

Selection: Complementary Th lymphocytes bind to foreign antigen on antigen presenting cell
Expansion : Th cells (rapid mitosis) -became memory cells or trigger hum oral response
Expansion: cytotoxic T cells
Action - secrete enzyme perforin - destroy infected cells

Question 26

Outline the process of hum oral response

Answer 26

Selection: Complementary Th lymphocytes bind to foreign antigen on antigen presenting T cells
Expansion: complementary B lymphocytes
Differentiate: B cells into plasma cells
Action : plasma cells secrete antibodies with complementary variable region to antigen

Question 27

Describe the structure and function of B lymphocytes

Answer 27

B cells differentiate into plasma cells to secrete antibodies

Question 28

Describe T lymphocytes

Answer 28

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

Question 29

What are memory cells

Answer 29

Specialised Th/B cells produced from primary immune response
Remain in low levels in the blood
Can divide very rapidly