Communicable diseases part 3

Question 1

How does aggulitinis work?

Answer 1

each antibody has two identical binding sites so is able to cross link by binding an antigen on one pathogen with one binding site and another pathogen with the other binding site this clumps them together then a phagocyte can engulf them at once

Question 2

Whate are the advantages of aggulitinins

Answer 2

physically impedes them from carrying out some fuctions such as invading host cells
can easily be destroyed and recongnised
very effective against viruses

Question 3

Why does the primary immune response take time

Answer 3

when first infected the immune system takes time to

• clonally expand
• clonal selection
• differentiation
• APC
• Lack of memory cells

Question 4

why doesn’t the secondary immune response take time

Answer 4

there are T and B memory cells so they regonise them more quickly and produce an immune response they are quicker and there is a higher concentration therefore no symptoms are felt

Question 5

draw the graph on immune response times

Answer 5

see revision guide

Question 6

What makes plants attractive to pathogens

Answer 6

plants have a wide range of sugars in photosynthesis these convert those sugars to many compounds such as proteins and oils which make the plant attractive to organisms

Question 7

what are passive defences

Answer 7

passive defences are defences are defences that are present before an infection, they prevent entry and spread of pathogen by the chemical and physical ways

Question 8

what are the physical defences of plants

Answer 8

cellulose cell wall
lignin thickening of cell walls
waxy cuticles
bark
stomatal closure
callose
formation of tylose

Question 9

describe what role cellulose in the cell wall plays (plant passive physical defences)

Answer 9

it acts as a physical barrier but most plant cell walls contain a variety of chemical defences that are induced when a pathogen is detected

Question 10

Describe what role the lignin thickening of the cell wall plays (plant passive physical defences)

Answer 10

waterproof and almost completely indigestible

Question 11

Describe what role waxy cuticles play (plant passive physical defences)

Answer 11

prevent water collecting on cell surfaces therefore waterborne pathogens cannot survive

Question 12

describe what role bark plays (plant passive physical defences)

Answer 12

bark contains a variety of chemical defences that work against pathogenic organisms

Question 13

Describe what role stomatal closure plays (plant passive physical defences)

Answer 13

stomata are points of entry therefore when pathogens are detected in a part of the plant the guard cells close the stomata and trap the pathogen preventing it from spreading

Question 14

Describe what role callose plays (plant passive physical defences)

Answer 14

large polysaccharide polymers are deposited in sieve tube elements at the end of the growing system in the sieve tube elements around sieve tube plates this blocks the flow in the sieve tube and can prevent a pathogen from spreading around the plant

Question 15

Describe what role tylose plays (plant passive physical defences)

Answer 15

a tylose is a balloon like swelling that fills the xylem vessel, the vessel can no longer carry water and this prevents the spread of pathogens, tylose contains a high concentration of terpenes that are toxic to the pathogen

Question 16

Name some chemical passive defences

Answer 16

some chemicals are passive such as terpenes but a lot of chemicals are active as it requires a lot of energy to make them

Question 17

What are active defences

Answer 17

when pathogens attack specific chemicals in pathogenic cell walls, for example proteins and glycolipids, are detected by the plant cell. this increases the passive defences and secretes chemicals

Question 18

Describe some active defences

Answer 18

• cell wall are stronger and more thickened with more cellulose
• oxidative bursts that produce highly reactive oxygen molecules are capable of damaging the cells of invading organisms
• callose between the plant cell wall and membrane near the invading pathogen, they deposit polysacchiraride polymers which impede cell wall penetration at the site of infection as well as strengthening the cell wall and blocking the plasmodesmata
• terepenoids, phenols, alkaloids, defensive proteins, and hydrolytic enzymes
• necrosis - deliberate cell suicide, this is activated by intracellular enzymes that are activated by injury they turn the leaves brown. this is when a few cells are sacrificed for the rest of the plant to survive (around the infected area), this traps the pathogen and stops it from getting nutrients and water therefore stops it from spreading
• canker - this is a sunken necrotic lesion in the woody tissue, it causes the death of cambium tissue in the bark and prevents spreading and entry

Question 19

What do terepenoids do (active chemical defence)

Answer 19

these are essential oils that have antibacterial and antifungal properties

Question 20

what do defensive proteins do (active chemical defence)

Answer 20

small cysteine rich proteins that have broad antimicrobial activity that act on molecules in plasma membranes of pathogens inhibiting action of ion transport channels

Question 21

What do phenols do? (active chemical defences)

Answer 21

have antibiotic and antifungal properties, tannins found in bark inhibit attack by insects
the tannins bind to the salivary proteins and digestive enzymes such as trypsin and chymotrypsin and deactivate them.
If insects digest a high concentration of these then it stops growth and the insect eventually dies

Question 22

What do alkaloids do? ( active chemical defences)

Answer 22

Nitrogen containing compounds such as caffeine give a bitter after taste this stops herbivores from feeding on them
also acts on metabolic reactions inhibiting or activating enzyme action this inhibits protein synthesis

Question 23

What do hydrolytic enzymes do? (active chemical defences)

Answer 23

found in spaces between cells, they include chitinases this breaks down the chitin in fungal walls, glycanases which hydrolyse the glyosidic bonds in glycan and lysozymes which are capable of degrading bacterial cell walls

Question 24

Why are new drugs needed

Answer 24

• new diseases are emerging
• still many diseases with no treatments
• some antibiotics treatments are becoming less effective

Question 25

who accidently discovered penicillin

Answer 25

Alexander Flemming

Question 26

who developed penicillin

Answer 26

Florey and Chain

Question 27

what are some of the traditional remedies that were used

Answer 27

Morphine - sap from an unripe poopy seed head
opium - from poppies, these were both used as anaesthetics as they reduced nervous action in the central nervous system so the person could not feel pain
- willow bark used to relieve pain and fever, the active ingredient was found in 1897 and was used to reduce the side effect of stomach bleeding by adding an acetyl group this lead to the making of aspirin and ibuprofen

Question 28

Name ways in which animals use medicine

Answer 28

• monkeys and bears and other animals rub citrus oil onto their coats as insecticides and antiseptics in order to prevent insect bites and infection

Question 29

How did plants help aspirin

Answer 29

research into plants allowed scientists to isolate the active ingredient, they analysed the molecule then manufactured similar molecules

Question 30

Why are we now using tropical plants

Answer 30

great diversity therefore they contain molecules that could form medicinal drugs

Question 31

what does screening do

Answer 31

enables scientists to screen chemicals more effectively for their potential use

Question 32

what do pharmaceutical companies do

Answer 32

they conduct research into the way microorganisms cause disease

Question 33

How do drugs stop disease from spreading

Answer 33

if binding site between pathogens and receptor can be blocked then disease causing pathogen cannot gain access to the cell,
the glycoprotein receptor molecule can be isolated and sequenced once the amino acid sequence is known molecular modelling can be used to determine the shape of a receptor and could be used to bind to the virus itself this blocking the virus from entering T-helper cells, it also can inhibit the action of certain enzymes

Question 34

How does personalised medicine work

Answer 34

one day it might be possible to sequence genes from individuals with a particular conditions and develop drugs for that condition

Question 35

what is synthetic biology used to do

Answer 35

used to construct new devices and systems

Question 36

Where are most antibiotics derived from

Answer 36

the genus streptomcyes

Question 37

What can cause antibiotic resistance

Answer 37

misuse can cause bacteria and fungi to develop a resistance and therefore current antibiotics have a limited effect