Topic 5 helath, disease and the development of medicines

Question 1

define health

Answer 1

complete physical, mental and social well-being not merely the absence of disease or infirmity

World Health Organisation (WHO)

Question 2

define communicable and non communicable disease

Answer 2

communicable - diseases that can be spread between individuals

non communicable - diseases that cannot be transferred or transmitted between individuals

Question 3

define susceptible

Answer 3

being susceptible to a disease means that you have an increased chance of getting it. for example if you already have one disease it could make you more susceptible to others because your body and immune may have become weakened by the diseases so it’s harder to fight off others.

Question 4

discuss cholera

Answer 4

pathogen - bacteria called bacterium cholerae
symptoms - diarrhoea
spread - by contaminated water
reduce/prevent - making sure people have access to clean water supplies

Question 5

discuss tuberculosis

Answer 5

pathogen - bacteria called mycobacterium tuberculosis
symptoms - coughing and lung damage
spread - through the air when infected individuals cough
reduce/prevent - infected people should avoid public places, practice good hygiene, sleep alone and ensure their homes are well-ventilated

Question 6

discuss malaria

Answer 6

pathogen - protist
symptoms - damage to red blood cells and in severe cases the liver
spread - mosquitos act as a vector (carrier)
reduce/prevent - use mosquito nets and insect repellents

Question 7

discuss stomach ulcers

Answer 7

pathogen - bacteria called helicobacter pylori
symptoms - stomach pain, nausea and vomiting
spread - oral transmission e.g swallowing contaminated food or water
reduce/prevent - having clean water supplies and hygienic living conditions

Question 8

discuss ebola

Answer 8

pathogen - ebola virus
symptoms - haemorrhagic fever (a fever with bleeding)
spread - bodily fluids
reduce/prevent - by isolating infected individuals and sterilising any areas where the virus is present

Question 9

discuss chalara ash dieback

Answer 9

pathogen - fungi that affects ash trees
symptoms - leaf loss and bark lesions
spread - carried through air by the wind and when diseased ash trees are moved between areas
reduce/prevent - removing young infected ash trees and restricting the import or movement of ash trees

Question 10

what is a virus

Answer 10

• a protein coat around a string of genetic material

- they have to infect living host cells to survive and reproduce

Question 11

discuss the lytic pathway of the virus life cycle

Answer 11

• the virus attaches itself to a specific host cell and injects its genetic material into the cell
• the virus uses proteins and enzymes in the host cell to replicate its genetic material and produce the components of new viruses
• the viral components assemble
• the host cells splits open releasing the new viruses which infect more cells

Question 12

discuss the lysogenic pathway of the virus life cycle

Answer 12

• the injected genetic material is incorporated into the genome (DNA) of the host cell
• the viral genetic material gets replicated along with the host DNA every time the host cell divides - but no new viruses are made because the virus is dormant (inactive)
• eventually a trigger e.g the presence of a chemical causes the viral genetic material to leave the genome and enter the lytic pathway

Question 13

discuss chlamydia

Answer 13

• It is an STI

pathogen - bacterium but it behaves in a similar way to a virus because it can only reproduce within host cells
symptom - can cause infertility in men and women
spread - bodily fluids
reduce/prevent - wear a condom during sex, screen individuals so they can be treat and avoid sexual contact

Question 14

discuss HIV

Answer 14

• It is an STI
• human immunodeficiency virus
• eventually leads to aids

Pathogen - virus
Symptoms - kills white blood cells which are very important in immune response. it eventually leads to aids (acquired immune deficiency syndrome) which is where and infected person’s immune system deteriorates and eventually fails and because of this the person becomes very vulnerable to opportunistic infections by other pathogens
Spread - infected bodily fluids in sex or sharing needles
Prevent/reduce - use a condom during sex, avoid sharing needles, medication can reduce risk of passing the virus onto others during sex or mother passing onto baby during pregnancy, screening and proper treatment

Question 15

what are some physical defences a plant has against disease

Answer 15

• waxy cuticle (barrier and stops water collecting on the leaf which could reduce the risk of infection by pathogens transferred in water)
• cell walls made of cellulose

Question 16

what are some chemical defences a plant has against disease

Answer 16

• produce chemicals called antiseptics which kill bacterial and fungal pathogens
• produce chemicals to deter pests (insects) from feeding on their leaves

Question 17

discuss how plant chemicals can be used to treat human disease or relieve symptoms

Answer 17

quinine - comes from the bark of the cinchona tree and for years it was the main treatment for malaria

aspirin - used to relieve pain and fever. It was developed from a chemical found in the bark and leaves of willow trees

Question 18

how can plant pathologists detect disease in the field by observations

Answer 18

by recognising symptoms and indicators

galls (abnormal growths) might indicate crown gall disease in many different types of plant including apple and other fruit trees

symptoms such as yellow leaves indicate environmental causes such as nutrient deficiency. By changing the environmental conditions e.g adding nutrients to the soil and observing any change in the plants symptoms it can be possible to determine weather a plant is diseased or whether the symptoms are due to something else

different pathogens are spread in different ways so plant pathologists can analyse the distribution of diseased plants to identify the kind of pathogen involved
patches of diseased plants may suggest that the disease is spread by the soil and a random distribution may suggest an airborne pathogen

Question 19

how can plant pathologists detect disease in the field in the lab

Answer 19

detecting antigens

• pathogens have unique molecules on their surface called antigens
• antigens from a particular pathogen will be present in a plant infected with that pathogen and can be detected in a sample of plant tissue using monoclonal antibodies
• the detection of an antigen unique to a particular pathogen allows that pathogen to be identified and the disease diagnosed

Detecting DNA

• If a plant is infected with a pathogen, the pathogen’s DNA will be present in the plants tissue
• scientists have techniques that allow them to detect even small amounts of pathogen DNA in a sample of plant tissue allowing them to identify the particular pathogen that is present

Question 20

what physical barriers against pathogens do humans have

Answer 20

• skin acts as a barrier and if it gets damaged blood clots quickly seal cuts and keep microorganisms out
• cillia sweeps pathogens out the mouth or down the hydrochloric acid in the stomach and waft the mucus up to the back of throat where it can be swallowed
• mucus traps pathogens so they can be coughed out

Question 21

what chemical barriers against pathogens do humans have

Answer 21

• stomach hydrochloric acid

- lysozyme in tears which kill bacteria on the surface of the eye

Question 22

what are B-lymphocytes

Answer 22

a type of white blood cell that are involved in the specific immune response

1) every pathogen has unique molecules (proteins) on their surface called antigens
2) when your B-lymphocytes come across an antigen on a pathogen they start to produce proteins called antibodies. Antibodies bind to the new invading pathogen so it can be found and destroyed by other white blood cells. The antibodies are specific so won’t bind to other pathogens
3) the antibodies are then produced rapidly and flow all round the body to find all similar pathogens

Question 23

when a pathogen enters the body for the first time what is the immune response like

Answer 23

slow because there aren’t as many B-lymphocytes that can make the antibody needed to bind to the antigen

Question 24

as well as antigens what are also produced in response to a foreign antigen

Answer 24

memory lymphocytes which will remain in the body for a long time and remember a specific antigen

Question 25

what does the possession memory lymphocytes mean

Answer 25

the person is now immune as their immune system has the ability to respond quickly to a second infection of the same pathogen

Question 26

discuss immunisation

Answer 26

• injecting a dead or inactive pathogens into the body
• they are antigenic so even though they are harmless they still carry antigens
• the body will the make antibodies to help destroy them
• the production of antibodies will also trigger the production of memory lymphocytes so if the same pathogen enters the body the secondary immune response will be quick and the person won’t get ill

Question 27

what are the pros of immunisation

Answer 27

• big outbreaks of disease called epidemics can be prevented if a large percentage of the population are immunised because there are less people able to pass on or catch the disease (herd immunity)
• some diseases like smallpox have being virtually wiped out due to immunisation

Question 28

what are the cons of immunisation

Answer 28

• it doesn’t always work

- you can sometimes have a bad allergic reaction to a vaccine

Question 29

what are monoclonal antibodies

Answer 29

lots of clones of one type of cell produced from one single B-lymphocyte. this means all the antibodies are identical and will target only one specific protein antigen

Question 30

how do you produce monoclonal antibodies

Answer 30

• lymphocytes don’t divide very easily
• tumour cells don’t produce antibodies but divide lots so can be grown really easily
• it is possible to fuse a mouse B-lymphocyte with a type of tumour cell called a myeloma cell to create a cell called a hybridoma
• hybridoma’s can be cloned to get lots of identical cells
• these can all divide really quickly to produce the same antibodies (monoclonal antibodies)
• these can be collected and purified
• you can make monoclonal antibodies that bind to any specific antigen you want and only target one specific antigen in the body

Question 31

discuss the use of monoclonal antibodies in pregnancy testing

Answer 31

a hormone (HCG) is found in the urine of woman only when they are pregnant and pregnancy testing sticks detect this.

1) the bit of the stick you wee on has some antibodies to the hormone on it with blue beads attached
2) the test strip (the bit of the stick that turns blue if your pregnant) has some more antibodies stuck to it that can’t move
3) If you’re pregnant and you wee on the stick
- the hormone binds to the antibodies on the blue beads
- the urine moves up the stick carrying the hormone and the beads
- do the blue beads get stuck on the strip turning it blue
4) if your not pregnant and you wee on the stick the urine still moves up the stick carrying the blue beads but there’s nothing to stick the blue beads onto the test strip so it doesn’t go blue

Question 32

what do cancer cells have and what can you do in the lab

Answer 32

they have proteins on their cell membranes that aren’t found on normal body cells called tumour markers
in the lab you can make monoclonal antibodies that will bind to these tumour markers and they can be used to help diagnose and treat cancer

Question 33

how can monoclonal antibodies be used to diagnose cancer cells

Answer 33

• the antibodies are labelled with a radioactive element
• the labelled antibodies are then given to the patient through a drip
• they go into the blood and are carried around the body
• when the antibodies come into contact with cancer cells they bind to tumour markers
• a picture of the patient’s body is taken using a special camera that detects radioactivity and anywhere that cancer cells are present will show up as a bright spot
• doctors can see exactly where the cancer is, what size it is and find out if its spreading

Question 34

how can monoclonal antibodies be used to treat cancer cells

Answer 34

• an anti-cancer drug is attached to monoclonal antibodies
• the antibodies are given to the patient through a drip
• the antibodies target specific cells (the cancer cells) because they only bind to tumour markers
• the drug kills the cancer cells but doesn’t kill any normal body cells near the tumour
• other cancer treatments (like other drugs and radiotherapy) can affect normal body cells as well as killing cancer cells
• so the side effects of an antibody based drug are lower than for other drugs for radiotherapy

Question 35

how can monoclonal antibodies be used to find blood clots

Answer 35

• when blood clots, proteins in the blood join together to form a solid mesh
• monoclonal antibodies have been developed that bind to these proteins
• you can attach a radioactive element to these antibodies
• then if you inject them into the body and take a picture using a camera that picks up radiation, that picture will have a really bright spot where there is a blood clot
• this is useful because you can easily find a potentially harmful blood clot and get rid of it before it harms the patient

Question 36

what does radiotherapy involve

Answer 36

firing high-energy beams (like X-rays) straight at a tumour