Defence against Disease and Drugs

Question 1

First Defences : Skin

Answer 1

A physical layer.
Rough top layer sheds, meaning that microorganisms and bacteria shed too.
Sebaceous glands produce antimicrobials.

Question 2

First Defences : Hair in Nose

Answer 2

Helps trap particles in a sticky layer of mucus ; removed by blowing or swallowing, which is taken care of in stomach

Question 3

First Defences : Trachea and Bronchi

Answer 3

Hair like projections - cilia
Mucus-producing cells ( goblet cells ) are mixed in with ciliated cells to keep a fresh lining of mucus. This traps large particles + microorganisms. Cilia waft mucus to the back of the throat to be swallowed and microorganisms are destroyed by stomach acid.
Many mitochondria for energy.

Question 4

First Defences : Stomach

Answer 4

Hydrochloric acid destroys cell wall of microorganisms and kills them ( pH 2 ). Coated with a special lining to prevent the stomach wall corroding.

Question 5

First Defences : Tears + Eyelashes

Answer 5

Trap dirt and microorganisms, preventing infections.
Tears have high salt content to dry up microorganisms, they also wash out microorganisms.

Question 6

Lysozyme

Answer 6

Enzyme in tears, breaks down bacterial cell walls.

Question 7

First Defences : Scabs

Answer 7

Repair physical barrier.
Formed from blood clots - platelets are exposed to the air, making fibrin. This stretches across the wound, forming a mesh. Additional red blood cells and platelets fill the mesh, forming a clot.

Question 8

Second Defences : Phagocytosis

Answer 8

1. Phagocytes leave the blood through capillary walls and enter blocked tissue.
2. Cell membrane and cytoplasm of the phagocyte surrounds the pathogen.
3. Pathogen is engulfed by phagocytosis.
4. Pathogen is digested by lytic enzymes. Useful substances are absorbed and waste substances are released via exocytosis. The phagocytes can continue to engulf more pathogens.

Question 9

Pathogen

Answer 9

A microorganism that causes disease.

Question 10

Third Defences : Lymphocytes

Answer 10

Lymphocytes produce antitoxins to neutralise the toxins from pathogens, making them safe. Antitoxins are specific to particular toxins.

Question 11

Antibody

Answer 11

A protective protein produced by the immune system (WBCs - phagocytes) in response to the presence of a foreign substance, called an antigen. They recognise and latch onto antigens in order to remove them from the body. They can either neutralise the pathogen by binding or initiate phagocytosis.

Question 12

Antigen

Answer 12

An antigen is a substance that is capable of stimulating an immune response. Often on the surface of a pathogen but can also be a toxin or a chemical.

Question 13

Vaccination

Answer 13

Involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the WBCs to produce antibodies. If the same pathogen re-enters the body, the WBCs respond quickly to produce the correct antibodies, preventing infection.

Question 14

Response to vaccine

Answer 14

Primary response : 1st exposure, correct antibodies made over 2-3 weeks
When pathogen destroyed, conc. of antibodies decrease, but not to zero due to memory cells ( WBCs that stay in your blood and remember how to make pathogen specific antibodies ) created
Secondary response : 2nd exposure - more antibodies created faster due to memory cells - no symptoms, not ill

Question 15

Small pox

Answer 15

A virus.
Cure found by Edward Jenner, who inoculated James Phipps with cowpox pus, which helped develop memory cells, which also fought smallpox as they were in a similar viral family.

Question 16

Issues with vaccines

Answer 16

Pathogen could mutate.
Not everyone will want to be vaccinated.
Side effects eg fever, chills, muscle pain, headache.

Question 17

Herd immunity

Answer 17

Mass vaccination programmes increase the number of people who are immune, making it harder for the pathogen to spread to nonimmunised people.

Question 18

Global vaccination problems

Answer 18

LICs have less access to healthcare.
Funding.
How the vaccine is rolled out - focus on densely populated areas

Question 19

Drug

Answer 19

Any chemical that alters how the body works.

Question 20

Main goals of medicines

Answer 20

Relieving symptoms.
Breaking / curing the underlying illness by destroying pathogens.

Question 21

Antibiotics

Answer 21

Only kill bacterial pathogens.
1. Interfere with a pathogens metabolism eg. prevent cell wall growth or block the actions of ribosomes ( cannot grow ).
2. Slow bacterial growth long enough for the immune system to get on top of them.
Don’t harm our own cells.
Specific bacteria have to be treated with specific antibiotics, however, there are some general ones eg. amoxicillin.

Question 22

Alexander Fleming

Answer 22

Discovered penicillin ( fungal mould )
He was investigating a strain of bacteria called Staphylococcus, growing them on petri dishes. He came back from holiday to find mould had contaminated one of his petri dishes, but there was no bacteria growing around it. He concluded that the mould must make a chemical that destroys the bacteria.
Name originated from the mould’s family, Penicillum.

Question 23

Antibiotic resistance

Answer 23

Mutation in DNA of bacteria, making it resistant to antibiotics. This mutated cell continues to divide by binary fission, creating a drug-resistant population.

Question 24

Reducing antibiotic resistant strains

Answer 24

Doctors should not prescribe antibiotics inappropriately.
Patients should complete a full course of antibiotics, so none survive, therefore can’t mutate.
Widespread agricultural use.

Question 25

Common antibiotic resistant strains

Answer 25

Antibiotic-resistant gonorrhea MRSA ( a hospital superbug )

Question 26

Painkillers

Answer 26

Stop nerve impulses transmitting pain messages to the brain, therefore limiting the feeling of pain. Mainly based on - aspirin, opiates ( from poppies )

Question 27

In the past, drugs were extracted from plants :

Answer 27

Foxglove provides heart drug, digitalis. Willow bark provides aspirin. Penicillin from penicillum mould.

Question 28

Antiviral drugs

Answer 28

Slow down viral development. Hard to manufacture a drug to kill a virus as they reproduce inside cells.

Question 29

Preclinical drug testing - Laboratory

Answer 29

Tests using computer models and human skin cells ( grown from stem cells ). Can test effectiveness and side effects. Fails if drug damages cells.

Question 30

Preclinical Drug testing - Animal

Answer 30

Continues to test for effectiveness, but also monitors side effects. Variety of animals used, but try to show relatedness to humans.

Question 31

Clinical drug testing

Answer 31

Phase 1 - healthy people, 20-80 volunteers (for safety and dosage) Phase 2 - infected people, 100-300 volunteers (for efficacy and side effects) Phase 3 - 3000+ volunteers, Double blind tests (Patients are randomly allocated into groups, one has drug, one has placebo), peer review (research checked by other experts for validity + ethics, before publication in scientific journals) Phase 4 - Doctors report on side effects - continues as long as medicine in circulation

Question 32

Placebo effect

Answer 32

People feel better as they believe they are taking the drug

Question 33

Monoclonal

Answer 33

All one type, MABs are copies of one type of antibody

Question 34

Lymphocytes cannot

Answer 34

divide after they begin to produce antibodies

Question 35

Method of making MABs

Answer 35

Mouse is injected with specific antigen to stimulate lymphocytes to make specific antibody. Extracted lymphocytes are combined with a specific tumour cell. Detergents used to break cell membranes and help fuse. Creates a hybridoma cell, which can divide and make antibodies. Screened to check for antibody production. Cloned to produce identical cells that produce same antibody ( these are MABs ) Large amount of MABs are collected and purified.

Question 36

Pregnancy tests

Answer 36

rely on monoclonal antibodies which bind to HCG, a hormone made in the early stages of pregnancy.

Question 37

MAB research use

Answer 37

Can carry fluorescent markers, which make it easy for doctors to see where they have built up. When the antibody binds to the specific antigen, it will fluoresce. This allows doctors to detect problems before they seriously affect a person's health.

Question 38

Antiseptic

Answer 38

A chemical that destroys pathogens outside the body.

Question 39

Parts of a pregnancy test

Answer 39

The reaction zone contains MABs, specific to HCG, with an enzyme attached that can activate dye molecules. The results zone contains immobilised MABs specific to HCG. The control zone contains immobilised antibodies complementary to the MABs from the reaction zone.

Question 40

How a pregnancy test works

Answer 40

When a pregnant woman's urine touches the reaction zone, HCG will bind to the MABs. As urine moves up the test, MABs, + their associated enzymes, are stopped in the results zone, as the MABs here also bind to HCG. The enzymes activate the dye, creating a blue line. Antibodies, + associated enzymes, not bound in the results zone move up into the control zone, where they bind to the immobilised antibodies. The enzymes react with the dye to show a second blue line.

Question 41

Pregnancy test if not pregnant

Answer 41

The free MABs will be stopped ONLY in the control zone, showing one blue line.

Question 42

MABs treatment use

Answer 42

1. an anti-cancer drug is attached to a monoclonal antibody ; the MABs bind to specific antigen on the cancer cell ; drugs either directly destroy cancel cell, or prevent cells from dividing and growing ; harmless to surrounding tissue. 2. Once bounds, trigger immune system to attack and destroy the cancer cells. 3. Make cancerous cells more identifiable to surgeons eg. clumping together or fluorescence.

Question 43

MAB treatment advantages

Answer 43

Healthy cells are unaffected Side effects easily treated Treat wide range of conditions Used in many different ways

Question 44

MAB treatment disadvantages

Answer 44

Expensive Many side effects eg. nausea, fever Difficult to get correct antibodies Ethical issues

Question 45

Antiseptic RQP variables

Answer 45

independent - type of antiseptic dependent - area of uninfected circle control - type of bacteria, volume of antiseptic, type of agar jelly, temperature

Question 46

Zone of inhibition

Answer 46

Area where no bacteria is growing

Question 47

Antiseptic RQP method

Answer 47

1.Wash hands to prevent contamination 2.Draw quarters onto petri dish and label each quarter with type of antiseptic. 3.Use a sterile pipette to add 100 microlitres of microbial culture to agar jelly. Keep lid as closed as possible throughout to prevent air microbes entering. 4. Sterilise a spreader by dipping in ethanol to kill bacteria, passing through a flame and allowing to cool. 5.Use spreader to gently spread microbial culture across the agar jelly. 6.Sterilise forceps. 7.Use forceps to soak a mast ring in an antiseptic and place in labelled quarter of petri dish. 8. Repeat 7 for each antiseptic. 9.Tape plate shut to prevent microbes from the air entering. 10.Wash hands. 11. Incubate at 25C for a week. 12. Measure diameter of zone of inhibition. 3. Calculate areas.