B3

Question 1

What is a pathogen?

Answer 1

a microorganism that causes disease

Question 2

What are the four types of pathogens?

Answer 2

1. protists
2. viruses
3. bacteria
4. fungi

Question 3

Give three ways that pathogens can be spread between people?

Answer 3

1. through the air- breathed in or spread by airborne droplets e.g. influenza virus
2. direct contact e.g. athlete’s foot
3. water- drinking or bathing in dirty water e.g. cholera

Question 4

Give three viral diseases

Answer 4

1. Measles
2. HIV
3. Tobacco Mosaic Virus(TMV)

Question 5

What is Tobacco Mosaic Virus?

Answer 5

a virus that can be transmitted by direct contact between plants (naturally or by the hands of farmers) which infects the chloroplasts of plant leaves and changes their colour from green to yellow or white in a mosaic pattern

• reduces the plant’s ability to photosynthesise and grow properly, which reduces the crop yield for farmers

Question 6

What happens when a plant has a nitrate deficiency?

Answer 6

Stunted growth

Question 7

What happens when a plant has a magnesium deficiency?

Answer 7

yellow leaves (discolouration) because magnesium helps with chlorophyll production

Question 8

What is HIV and how can you treat it?

Answer 8

a viral disease that is spread by unprotected sex, sharing needles or infected blood. It attacks white blood cells and can develop into AIDS

antiretroviral drugs

Question 9

Why might someone with AIDS take longer to recover from salmonella?

Answer 9

Their immune system would be weakened so their white blood cells would not be able to destroy the bacteria

Question 10

Name a fungal disease

Answer 10

Rose black spots (causes purple/black spots to form on the leaves of roses)

Question 11

How are protists usually transported?

Answer 11

By vectors (other organisms that do not get the disease)

Question 12

What is a parasite?

Answer 12

An organism that depends on another organism to grow and reproduce

Question 13

What is malaria caused by?

Answer 13

Malaria is caused by parasitic protists which means it needs a host to survive, transported between hosts by mosquitos.

Question 14

Give symptoms of malaria

Answer 14

• high fever
• pain
• diarrhoea
• vomiting
• sweat and chills

Question 15

Give two bacterial diseases and two symptoms of each

Answer 15

Salmonella
- fever
- stomach cramps
- vomiting
- diarrhoea

Gonorrhoea
- thick yellow/green discharge
- pain when urinating

Question 16

Give four ways to reduce/prevent the spread of disease and explain

Answer 16

1. being hygienic- using simple hygienic measures such as washing your hands thoroughly before preparing food or after sneezing
2. destroying vectors- by getting rid of the organisms/ their breeding sites that spread disease you can prevent the disease being passed on
3. isolating infected individuals- prevents the individual from passing it on
4. vaccinations- stops people from being able to develop the disease, therefore reduces risks of it being spread

Question 17

How does our first line of defence protect us from pathogens?

Answer 17

• skin acts as a physical barrier, it also secretes antimicrobial substances which kill pathogens
• nose is filled with little hairs and mucus which can trap the pathogens and any other particles
• trachea and bronchi are covered in a layer of mucus which would trap any particles and are lined with cilia, which waft the mucus up to the back of the throat(where it can be swallowed) to prevent the build up of this mucus
• stomach produces hydrochloric acid, which is very acidic and kills the pathogens

Question 18

How does our immune system defend us against pathogens?

Answer 18

White blood cells continually patrol the blood circulating in our body

Question 19

What are antigens?

Answer 19

antigens are unique substances on the surface of invading pathogens which our immune system detects as being foreign

Question 20

What is a vaccine and how does it work?

Answer 20

an altered/weakened/inactivated form of a pathogen that are injected into the body.

• They carry antigens = our body produces antibodies to attack them even though they are harmless. This means if live pathogens of the same type enter the body again the white blood cells can rapidly mass-produce antibodies to kill off the pathogen

Question 21

How does antibiotic resistance arise in a population of bacteria?

Answer 21

Antibiotic resistance happens when bacteria develop mutations in their DNA which can change their characteristics and this could result in the bacteria being less affected by the antibiotic.
The resistant bacteria quickly forms a new colony of its own which all have the gene for antibiotic resistance= an antibiotic resistant strain

Question 22

What is the difference between painkillers and antibiotics?

Answer 22

painkillers relieve symptoms of disease whilst antibiotics kill or prevent the growth of bacteria therefore curing the problem

Question 23

Which plant does aspirin originate from?

Answer 23

willow

Question 24

Which plant does digitalis originate from?

Answer 24

foxgloves

Question 25

What are the three main functions of white blood cells?

Answer 25

1. phagocytosis- certain white blood cells directly engulf pathogens. - by tracking the pathogen - binding to them - engulfing them at which point they kill the pathogen 2. producing anti-toxins anti-toxins are small molecules that can bind and counteract the toxins produced by bacteria 3. producing antibodies - antibodies are small proteins made by our white blood cells that can lock onto these foreign antigens and act as signals to tell our white blood cells to destroy them - each of our antibodies is specific for a particular antigen - once our immune system knows which antibody binds to the antigen, they are produced rapidly the next time the person is infected with the same pathogen to destroy it before it get a chance to develop - immune to that disease

Question 26

What is a placebo?

Answer 26

A substance that is similar to the drug being tested however it does not do anything

Question 27

What is a double blind clinical trial?

Answer 27

This is when both the patient in the study and the doctor do not know whether they have received the drug or placebo until all the results have been gathered to prevent any subconscious influence

Question 28

What are the three main stages in drug testing?

Answer 28

1. Preclinical testing- drugs are tested on human cells and tissues 2. Next step in preclinical testing is to test the drug on live animals (tests efficacy and finds out about its toxicity) 3. If the drug passes then it is tested on human volunteers in a clinical trial (first it is tested on healthy volunteers to ensure there are no side effects)

Question 29

What is a monoclonal antibody?

Answer 29

A monoclonal antibody is an antibody made from a single clone of cells

Question 30

How can a monoclonal antibody be produced (using a mouse)?

Answer 30

- inject a mouse with an antigen - then we extract the lymphocytes that make the specific antibody we want - we combine this with the tumour cell to form a hybridoma cell - we clone and harvest the antibodies

Question 31

What are some uses of monoclonal antibodies?

Answer 31

- for diagnosis e.g. in pregnancy tests - in laboratories to measure the levels of hormones and other chemicals in blood, or to detect pathogens - in research to locate and identify specific molecules in a cell/tissue by binding to them with a fluorescent dye - to treat some diseases e.g. cancer

Question 32

How can monoclonal antibodies be used to treat cancer?

Answer 32

The monoclonal antibody can be bound to a radioactive substance, a toxic drug or a chemical which stops the cells from growing and dividing.