Health and disease

Question 1

What are communicable diseases?

Answer 1

Diseases that can be spread between induviduals

Question 2

What are non communicable diseases?

Answer 2

-Diseases that cannot be transmitted between induviduals
-If you are infected by one disease, you are more susceptible to others

Question 3

What are pathogens?

Answer 3

Organisms such as viruses, protists, bacteria and fungi that cause communicable diseases

Question 4

A disease caused by Virus (viral):

Answer 4

Ebola
-causes haemorrhagic fever
-spread via bodily fluids
-transmission can be reduced by isolating infected induviduals and sterilising any areas where the virus may be present

Question 5

Name a fungal disease:

Answer 5

Chalara Ash Dieback
-symptoms include bark lesions and leaf loss
-fungus is carried through air by wind
-transmission reduced by removing young, infected ash trees and replanting with different species

Question 6

Name a disease caused by a protist:

Answer 6

Malaria
-effects of malaria include damage to red blood cells and liver
-mosquitoes act as vectors - they pass on the protist to humans but don’t get the disease themselves
-mosquito nets and insect repellent can be used to prevent mosquitoes from biting

Question 7

Name a bacterial disease:

Answer 7

Cholera
-Causes diarrhoea
-Spreads through contaminated water sources
-Transmission can be reduced by making sure that people have access to clean water supplies

Question 8

An example of an STI:

Answer 8

HIV
-Human Immunodeficiency Virus - it kills white blood cells, which are really important for immune response
-HIV eventually leads to AIDS, where an infected persons immune system fails
-spread via bodily fluids (e.g blood, semen, vaginal fluids).

Question 9

What is a virus?

Answer 9

-A protein coat around a strand of genetic material
-have to infect host cells in order to reproduce

Question 10

The lytic pathway (step-by-step)

Answer 10

1) Virus attaches itself to a specific host cell and injects its genetic material into the cell
2) The virus uses proteins and enzymes in the host cell to replicate its genetic material and produce the components of new viruses
3) The viral components assemble
4) The host cell lyses, releasing the new viruses, which infect , more cells

Question 11

The lysogenic pathway

Answer 11

1) The genetic material is incorporated into the genome of the host cell
2) The viral genetic material gets replicated along with the host DNA every time the host cell divides - virus is dormant and no new viruses are made
3) 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 12

Example of plants physical defenses:

Answer 12

-Most plants and leaves have a waxy cuticle, providing a barrier to stop pathogens/pests.
-Also stops water collecting which reduces the risk of infection by pathogens transferred by water
-Have cell walls made from cellulose

Question 13

Examples of chemical defenses in plants:

Answer 13

-Produce chemicals called antiseptics which kill bacterial and fungal pathogens.
-Produce chemicals to deter pests from feeding on leaves
-These can be used as drugs to treat human disease (e.g Qunine and Aspirin)

Question 14

Physical barriers to stop pathogens entering the body:

Answer 14

-skin act as a barrier to pathogens, if damaged, blood clots quickly seal cuts
-hairs and mucus in nose trap particles that could have pathogens
-cells in trachea and bronchi also produce mucus, trapping pathogens

Question 15

Chemical barriers to stop pathogens entering the body:

Answer 15

-The stomach produces hydrochloric acid, kills most pathogens swallowed
-eyes produce lysozyme in tears, killing bacteria on the surface of the eye.

Question 16

How does an immune response to a specific pathogen work?

Answer 16

1) every pathogen has unique molecules (proteins) on its surface called an antigen

2) when white blood cells come across an antigen on a pathogen, they start to produce antibodies

3) antibodies bind to specifically the new invading pathogen, so can be found by other white blood cells, they won’t lock on to any other pathogens

4) the antibodies are then produced rapidly and flow all around the body to find similar pathogens

Question 17

Why is the first response slow to fighting a pathogen in the body?

Answer 17

-as when pathogen first enters the body, there aren’t many B-lymphocytes that can make the specific antibody needed to ‘lock on’ to antigen

Question 18

What are memory lymphocytes?

Answer 18

-produced in response to a foreign antigen
-remain in the body for a long time, and ‘remember’ a specific antigen

Question 19

Why are memory lymphocytes so important?

Answer 19

-as it ensures the person is now immune
-because their immune system has the ability to respond quickly to a second infection

Question 20

Is the secondary immune response faster/slower? Why?

Answer 20

-if the same pathogen enters the body again, there are more cells that will recognise it and produces antibodies
-this secondary immune response is faster and stronger

Question 21

How does immunisation work?

Answer 21

-injecting dead or inactive pathogens into the body
-these are antigenic, so your body makes antibodies to help destroy them as well as memory lymphocytes
-so if live pathogens of same type enter body, there will be memory lymphocytes that can cause a fast secondary immune response

Question 22

Advantages of immunisation

Answer 22

-Epidemics can be prevented if a large percentage of the population are immunised
-Some diseases (e.g smallpox) have been virtually wiped out by immunisation programmes

Question 23

What is herd immunity?

Answer 23

-If a large percentage of a population are immunised against a disease, even those who aren’t immunised are unlikely to catch the disease as there is fewer people to pass it on to you

Question 24

Disadvantages of Immunisation

Answer 24

• Doesn’t always work - sometimes it doesn’t give immunity
• Sometimes you can have a bad reaction to a vaccine (e.g swelling, or maybe something more serious like a fever or seizures)

Question 25

What are monoclonal antibodies?

Answer 25

• Produced by B-lymphocytes
• Produced from lots of clones of a single B- lymphocyte, meaning all the antibodies are identical
  -Means they will only target one specific protein antigen

Question 26

How do you make monoclonal antibodies?

Answer 26

To get the lymphocyte:
- Inject a mouse with chosen antigen
- Take B-lymphocytes produced by mouse

To get hybridoma:
- Fuse the B-lymphocyte with fast dividing tumour cells from the lab to get hybridoma

This then divides quickly to produce lots of clones that produce the monoclonal antibodies

Question 27

Why are monoclonal antibodies useful?

Answer 27

As they will only bind to the molecule that it is programmed to, meaning you can target them at a specific cell or chemical in the body

Question 28

How are monoclonal antibodies used in pregnancy tests?

Answer 28

• The part of the pregnancy test you wee on has antibodies to HCG (hormone produced while being pregnant) with blue beads attached to it
• The test strip has some more antibodies to the hormone stuck onto it (so they can’t move)

If you’re pregnant and wee on the stick:
- Hormone binds to the antibodies on blue beads
- Urine moves up the stick carrying hormone and beads
- beads and the hormone bind to the antibodies on the strip
-blue beads get stuck on the strip, turning it blue

If you’re not pregnant and wee on the stick:
- The urine moves up the stick carrying the blue beads
- There’s nothing for the blue beads to stick to, so it doesn’t go blue

Question 29

How can monoclonal antibodies be used to find blood clots?

Answer 29

-When blood clots, proteins in the blood join together to form a solid mesh
-Monoclonal antibodies have been developed that bind to these specific 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, the picture will have a really bright spot where a blood clot is present

Question 30

How do monoclonal antibodies target cancer cells?

Answer 30

-Cancer cells have proteins on their cell membranes that aren’t found on normal body cells
-you can make monoclonal antibodies that will bind to these which can be seen on a special radioactivity detecting camera
-doctors can see exactly what size it is, where it is and if it is spreading

Question 31

How are antibiotics used to treat bacterial infections?

Answer 31

-work by inhibiting processes in bacterial cells, but not in host organism
-an example is some antibiotics inhibit the building of bacterial cell walls - this prevents the bacteria from dividing and eventually kills them
-has no effect on the human host

Question 32

Why is it difficult to develop drugs to destroy a virus?

Answer 32

-Because viruses use your own body cells to reproduce, making it very difficult to develop drugs that destroy just the virus without killing the body’s cells

Question 33

What is the first stage of developing a new drug?

Answer 33

Preclinical Testing:
- Once a drug is discovered, it needs to be developed
- Drugs are first tested on human cells and tissue in the lab
- Next step is to test drug on live animals to test the drug works and to find the best dosage for the drug

Question 34

What is the second stage of developing a drug?

Answer 34

Clinical Testing:
- If drug passes the tests on animals, then it’s testes on human volunteers
- Firstly tested on healthy people to ensure no side effects, then is tested on people suffering from the illness
- Patients are randomly put into two groups. One is given the new drug and one is given a sugar pill to test the placebo effect
- Once the drug has finally passed, it will be approved by a medical agency before it can be used to treat patients

Question 35

How do you grow bacteria in a lab?

Answer 35

You have to make an agar plate which will form invisible colonies of bacteria on the surface of the jelly:
-Pour hot agar jelly into a Petri dish
-When the jelly is cooled and set, a sterile pipette and spreader can be used to get an even covering of bacteria
-the microorganisms then multiply

Question 36

How do you investigate the effect of substances on bacterial growth?