Topic 3: Infection and Response

Question 1

What is a pathogen?

Answer 1

A microorganism that causes disease, such as bacteria, viruses, fungi, or protists.

Question 2

How do bacteria harm the body?

Answer 2

Bacteria produce toxins and reproduce rapidly, damaging tissues.

Question 3

How do viruses harm the body?

Answer 3

Viruses invade cells, replicate, and burst out, destroying the cells.

Question 4

What causes measles, how is it spread, and how can it be prevented?

Answer 4

Measles is caused by a virus; spread by droplets (person coughing or sneezing); causes rash and fever; prevented by vaccination.

Question 5

What causes HIV, how is it spread, and how can it be prevented?

Answer 5

Human Immunodeficiency Virus spreads through the exchange of body fluids (blood) and sexual contact; can lead to AIDS (weak immune system); flu-like symptoms; prevented by using protection; treatment is antiretroviral drugs

Question 6

What causes Tobacco Mosaic Virus (TMV), how is it spread, and how can it be prevented?

Answer 6

TMV is a plant virus spread by contact or contaminated tools; photosynthesis can’t take place (can’t produce enough sugars for growth); prevented by hygiene and removing infected plants.

Question 7

What causes salmonella, how is it spread, and how can it be prevented?

Answer 7

Salmonella is a bacterium spread by contaminated food; cause fever, stomach cramps, vomiting and diarrhoea; prevented by cooking food properly and vaccinating poultry.

Question 8

What causes gonorrhoea, how is it spread, and how can it be prevented?

Answer 8

Gonorrhoea is a bacterial STD (sexually transmitted disease) spread by unprotected sex; symptoms are pain when urinating and yellow/green discharge; prevented by using condoms and treating with antibiotics (penicillin no longer works - become resistant).

Question 9

What causes rose black spot, how is it spread, and how can it be prevented?

Answer 9

It is caused by a fungus, spread by wind or water; reduces ability to photosynthesise so don’t grow well; prevented by removing infected leaves and using fungicides.

Question 10

What causes malaria, how is it spread, and how can it be prevented?

Answer 10

Malaria is caused by a protist spread by mosquito bites; prevented with mosquito nets and insect repellents (stops them feeding) or destroy their breeding sites and killing with insecticides (reducing the number).

Question 11

How does the skin defend against pathogens?

Answer 11

It acts as a physical barrier.
It secrets oils and antimicrobial substances (kills pathogens).

Question 12

How does the nose help defend against pathogens?

Answer 12

It has lots of little hairs and mucus to trap pathogens.

Question 13

How do the trachea and bronchi defend against pathogens?

Answer 13

They are covered in a layer of mucus, which traps any particles. To prevent mucus from building up, they are lined with cilia (tiny finger-like structures), and they move particles to the back of the throat to swollow it.

Question 14

How does the stomach help defend against pathogens?

Answer 14

Chemical barrier:
Produces hydrochloric acid (really strong) with a pH of 2. It kills nearly all pathogens.

Question 15

What is phagocytosis?

Answer 15

White blood cells engulf invading pathogens. They track them down and bind to them.

Question 16

How do white blood cells use antibodies?

Answer 16

They produce antibodies (small proteins) that lock onto foreign antigens on pathogens and act as signals to tell white blood cells to destroy them. Each antibody is specific for a particular antigen.

Question 17

What are antitoxins?

Answer 17

Substances made by white blood cells to neutralise/counteract the toxins produced by bacteria.

Question 18

How does vaccination prevent illness in an individual?

Answer 18

It introduces a small, safe amount of a weakened or inactive pathogen to stimulate white blood cells to produce memory cells and antibodies for quick future response.

Question 19

How does vaccinating a large population reduce the spread of disease?

Answer 19

It creates herd immunity, making it harder for the pathogen to spread.

Question 20

What is the role of antibiotics?

Answer 20

They kill or inhibit the growth of bacteria without harming human cells.

Question 21

What is the role of painkillers?

Answer 21

They relieve symptoms but do not kill pathogens.

Question 22

Why is antibiotic resistance a problem?

Answer 22

This is when bacteria evolves so that antibiotics can no longer kill them.

It makes bacterial infections harder to treat as antibiotics become less effective.

Question 23

What are the stages of drug testing before use?

Answer 23

Preclinical: Testing on cells, tissues, and animals to check safety and effectiveness.

Clinical: Testing on human volunteers to monitor side effects, dosage, and how well it works.

Question 24

Name three ways pathogens can be spread

Answer 24

• Through air (eg. coughing, sneezing)
• Direct contact
• Contaminated food or water

Question 25

How can the spread of diseases be reduced or prevented?

Answer 25

Through hygiene, isolating infected individuals, vaccinations and controlling/killing vectors.

Question 26

What are plant physical defences against disease?

Answer 26

Waxy cuticles, cell walls, and bark (layers of dead cells) protect against pathogens.

Question 27

What are plant chemical defences?

Answer 27

Production of antibacterial chemicals and poisons to deter herbivores.

Question 28

What are plant mechanical defences?

Answer 28

Thorns, hairs, leaves that curl when insects land on them, and mimicking other organisms to trick animals.

Question 29

What signs show a plant might be diseased?

Answer 29

Discoloured leaves, stunted growth, spots, abnormal growths, or pests.

Question 30

What are fungi?

Answer 30

Eukaryotic organisms. They can be unicellular (eg. yeast) or multicellular (eg. mushrooms). 🍄

Question 31

What are protists?

Answer 31

Eukaryotes, majority are unicellular organisms. Some are parasites: live on or inside another organism. Often transported by vectors: transport protists between different hosts (eg. mosquitos)

Question 32

What are the three things to check when testing drugs?

Answer 32

Efficacy ➡️ how well the drug works (effects) Toxicity ➡️ how harmful the drug is, side effects Dosage ➡️ how much of the drug or concentration should be given

Question 33

How to check validity of testing?

Answer 33

Clinical trials should be blind and use a placebo. This is a substance that is just like the real drug but doesn’t do anything. We don’t tell them which drug they’re taking. A double-blind trial is when neither the doctor nor volunteers know which drugs they’re taking until results have been analysed at the end of the study. Purpose is to avoid bias.

Question 34

What are monoclonal antibodies?

Answer 34

Antibodies made from clones of a single type of cell.

Question 35

What hormone does a pregnancy test detect?

Answer 35

Human chorionic gonadotropin (hCG) is the hormone produced by women that are pregnant. The test uses monoclonal antibodies

Question 36

What are the types of white blood cells?

Answer 36

Phagocytes ➡️ non-specific response, engulf pathogens and digest them using enzymes Lymphocytes ➡️ specific immune response, produce antibodies that bind to specific antigens on the pathogen’s surface Memory lymphocytes ➡️ made after an infection or vaccination, remember the pathogen so the body can respond faster/stronger if it returns