Biology - disease, defence and treatment

Question 1

What are pathogens?

Answer 1

Micro-organisms that can cause disease

Question 2

What are the four main types of pathogens and what do they cause?

Answer 2

1) Virus - HIV
2) Bacterium - Salmonella
3) Fungus - Athletes foot
4) Protist - Malaria

Question 3

What is the life cycle of a pathogen?

Answer 3

They infect a host, reproduce themselves (or replicate, in the case of a virus), spread from their host, and infect other organisms.

Question 4

What are communicable diseases?

Answer 4

A disease caused by a pathogen which means it is transmitted from one person to another rather than being inherited or caused by an environmental factor.

Question 5

What features do all bacteria cells have?

Answer 5

-no nucleus
-a cell wall made of murein
-a cell membrane and cytoplasm
-chromosome that is loose in the cytoplasm in a long loop
-may contain small loops of DNA called plasmids
-no chloroplasts or mitochondria
-exist as single cells
-may have pili to attach to surfaces, or flagella to allow them to move

Question 6

What is a virus?

Answer 6

-An ultramicroscopic infectious non-cellular organism that can replicate inside the cells of living hosts, with negative consequences.
-They are not considered alive as they do not complete all of the seven life processes, ie movement, respiration, sensitivity, nutrition, excretion, reproduction and growth.

Question 7

What are the types of ways disease can be transmitted?

Answer 7

Direct contact - Sex, shaking hands
Water - Dirty water transmits many diseases
Air - Sneezing, coughing
Unhygienic food preparation - Undercooked or reheated foods
Vector - An organism that can spread a disease. Badgers, rats, mosquitoes

Question 8

What is HIV?

Answer 8

Human Immunodeficiency Virus - Transmitted through bodily fluids in sex, cuts, and injections with shared needles.

Question 9

What is AIDS?

Answer 9

Acquired Immune Deficiency Syndrome - Develops after months or years of having HIV. Starts attacking immune system.

Question 10

What is chlamydia?

Answer 10

A disease transmitted by sex. Spread can be prevented using condoms. Can be treated using antibiotics. If left untreated it can cause infertility in adults and can cause conjunctivitis in babies.

Question 11

What is malaria?

Answer 11

A disease spread by mosquitoes by sucking infected blood from one person and passing it on to the next. Mosquitoes are called vectors as they transmit the disease without becoming ill themselves. Symptoms include sweats, fever, headache vomiting etc. There is no vaccination.

Question 12

How do people prevent getting malaria?

Answer 12

There is no vaccination so the infection can only be prevented if people do not get bitten.
People sleep under mosquito nets and wear insect repellent to avoid bites.

Question 13

How does skin prevent infection?

Answer 13

-The skin covers almost all parts of your body to prevent infection from pathogens.
-If it is cut or grazed, it immediately begins to heal itself, often by forming a scab.
-It is a non-specific first line of defence

Question 14

What are non specific barriers?

Answer 14

-First lines of defence to stop pathogens from entering your body. These first lines are general defences, and are not specific to fight against certain types of pathogen.
-These include skin, nose, trachea and stomach

Question 15

How does the nose prevent infection?

Answer 15

• The nose has internal hairs, which act as a physical barrier to infection.
• Cells in the nose produce mucus which traps pathogens before they can enter the lungs.
• It is a non-specific first line of defence

Question 16

How do the trachea and bronchi prevent infection?

Answer 16

• The trachea is lined with cilia which waft their hairs and move pathogens and mucus up towards the throat where they can be swallowed.
• Goblet cells produce mucus which traps the pathogens.
• It is a non-specific first line of defence

Question 17

How does the stomach prevent infection?

Answer 17

-It contains hydrochloric acid (stomach acid), which is strong enough to kill any pathogens that have been caught in mucus in the airways or consumed in food or water.
-It is a non-specific first line of defence

Question 18

What is the second line of defence?

Answer 18

The immune system - consists of phagocytes and lymphocytes

Question 19

What do phagocytes do?

Answer 19

-Phagocytes are a type of white blood cell
-Phagocytes are attracted to pathogens in the blood and bind to them. The phagocyte’s membrane surrounds the pathogen and engulfs it. Enzymes found inside the cell then break down the pathogen in order to destroy it.
-As phagocytes do this to all pathogens that they encounter, they are called non-specific.

Question 20

What do lymphocytes do?

Answer 20

-Lymphocytes are another type of white blood cell.
-They recognise proteins on the surface of pathogens called antigens. Lymphocytes detect that these are foreign and produce antibodies.
-The antibodies cause pathogens to stick together and make it easier for phagocytes to engulf them.

Question 21

What are antitoxins?

Answer 21

Some pathogens produce toxins which make you feel ill. Lymphocytes can also produce antitoxins to neutralise these toxins.

Question 22

What are memory cells?

Answer 22

If your body encounters a particular antigen, your lymphocytes might recognise it. If they do, they clone themselves in order to make enough antibodies to destroy the pathogen. Memory cells are also created which remain in your bloodstream and produce a quick response if the antigen is encountered again. You are then said to be immune.

Question 23

What are a few things parents have to consider when vaccinating their child?

Answer 23

-There is a risk associated with any injection. However, the risk of contracting a serious disease is far greater.
- Immunising increases herd immunity, ie those who are unable to be vaccinated are protected as outbreaks of disease are prevented because others have been vaccinated and are therefore immune.

Question 24

How do vaccines work?

Answer 24

1) A dead version of the virus is injected into the body.
2) Lymphocytes recognise the foreign pathogens and produce antibodies to the specific antigen.
3) The lymphocyte cell divides repeatedly producing many clones of the cell all producing the same specific antibody.
4) Once the microorganisms have been destroyed all the clone cells die off except a few.
These cells are memory cells.
5) If the same microbe is encountered again the antibodies will be produced faster and in larger numbers, hopefully destroying the microbes before symptoms are felt. This is immunity.

Question 25

How do white blood cells work in primary and secondary response?

Answer 25

During the primary infection, the antibodies slowly increase, peak at around ten days, and then gradually decrease.
A second exposure to the same pathogen causes the white blood cells to respond quickly in order to produce lots of the relevant antibodies, which prevents infection.

Question 26

What are antibiotics?

Answer 26

Antibiotics are substances that slow down or stop the growth of bacteria. Examples include penicillin and amoxicillin. These can be taken to cure the disease by killing the pathogen, but are only effective against bacterial diseases, not viral ones.

Question 27

What are viral diseases?

Answer 27

Viral diseases cannot be cured by antibiotics, because they reproduce inside the host cells.

Question 28

How do antibiotics work?

Answer 28

Antibiotics damage the bacterial cells but do not damage the host cells. However, they do not work for viral diseases as they reproduce in the host cell.

Question 29

What are the problems with antibiotics?

Answer 29

-overuse of antibiotics making them ineffective
-failing to complete the fully prescribed course by a doctor
-use of antibiotics in farming

Question 30

What is antibiotic resistance?

Answer 30

The ability of certain bacteria to survive and reproduce in the presence of an antibiotic. - superbugs

Question 31

What are the stages of preclinical testing?

Answer 31

1) Testing on human cells grown in the laboratory.
2) Testing on animals.
3) Testing on healthy human volunteers.

Question 32

What strategies are used in clinical drug testing to avoid bias?

Answer 32

Placebo - A placebo is a pill that does not contain the active ingredient, and so should have no effect whatsoever on the patient.
Blind trials – The patients are not told if they are in the trial group or the placebo/control group.
Double blind trials – Neither the patient nor the doctor administering the drug knows if the patient is receiving the drug or a placebo in an attempt to eliminate bias altogether.

Question 33

What are monoclonal antibodies?

Answer 33

‘Mono’ means one and ‘clone’ means identical copy. Monoclonal antibodies are, therefore, identical copies of one type of antibody.

Question 34

How are monoclonal antibodies formed?(rats)

Answer 34

1) An antigen is injected into a mouse.
2) The mouse naturally produces lymphocytes, which produce antibodies specific to the antigen.
3) Spleen cells which produce the lymphocytes are removed during a small operation.
4) The spleen cells are fused with human cancerous white blood cells called myeloma cells to form hybridoma cells which divide indefinitely.
5) These hybridoma cells divide and produce millions of monoclonal antibodies specific to the original antigen.

Question 35

What are the uses of monoclonal antibodies?

Answer 35

When injected into a person’s body, the monoclonal antibodies will bind with cancer cells and clump them together. This makes it easier to identify a cancerous tumour, which can then be treated or removed.

Question 36

How can monoclonal antibodies treat cancer?

Answer 36

-carrying drugs that have been attached to them to the tumour
-encouraging your immune system to attack the cancer cells directly

Question 37

What is tissue typing?

Answer 37

If a person requires an organ transplant, they must wait until a suitable match is found. A suitable match means their tissue type matches the donor organ.

Question 38

Why is tissue typing used?

Answer 38

A tissue type is used to determine the extent to which the immune system of the recipient of a donor organ will react against the donor organ antigens. A poor match could result in the rejection of a donor organ.

Question 39

How do monoclonal antibodies help with organ transplants?

Answer 39

Monoclonal antibodies have been developed which can prevent rejection. They combine with and inactivate helper T cells (These cells signal to other cells of the immune system that an antigen is present), without which the lymphocytes that produce antibodies against the transplanted organ won’t work.