B2 Defending Against Pathogens

Question 1

What type of defences does the human body use?

Answer 1

Non-specific defences, always present

Physical, Chemical, Microbial, the Immune system

Question 2

List physical defences (3)

Answer 2

Respiratory tract, skin, platelets

Question 3

What is the respiratory tract?

Answer 3

Nasal passage, trachea, lungs

Question 4

What are cilia?

Answer 4

Hair like structures that waft the mucus to the back of the throat where it can be swallowed

Question 5

How does the respiratory tract defend against pathogens?

Answer 5

It is lined with mucus and cilia, the mucus traps particles and the cilia wafts the mucus to the back of the throat where it can be swallowed.

Question 6

How does the skin defend against pathogens?

Answer 6

The skin acts as a barrier to pathogens

Question 7

How do platelets act as a defence against pathogens?

Answer 7

Platelets in the blood clump together to plug the wound (blood clotting) this stops you losing blood and prevents microorganisms entering the blood.

Question 8

List chemical defences(3)

Answer 8

Eyes, saliva, stomach acid

Question 9

How do the eyes defend against pathogens?

Answer 9

Tears produce an enzyme called lysozyme which breaks down bacteria on the surface of the eyes.

Question 10

What is the enzyme in tears called?

Answer 10

Lysozyme

Question 11

How does the mouth defend against pathogens?

Answer 11

Saliva contains molecules that kill pathogens to prevent them reaching the stomach

Question 12

How does the stomach defend against pathogens?

Answer 12

Produces hydrochloride acid, this kills the pathogens.

Question 13

What are the body’s microbial defences?

Answer 13

Some pathogens make it past the saliva and the stomach acid in the gut. The have to compete with the Bacteria in the gut to survive.

Question 14

What is the final defences of the body?

Answer 14

The immune system

Question 15

Explain a plants physical defences against pathogens

Answer 15

Leaves have a waxy cuticle, which acts as a waterproof barrier.

Plant cells are surrounded by cellulose, this is a physical barrier against pathogens which have made it past the cuticle.

Question 16

Explain a plants immune system

Answer 16

If a pathogen crosses a plants physical defences, it detects it and responds by producing anti microbial substances as a form of chemical defence.

Question 17

What are phytoalexins?

Answer 17

Anti microbial substance produced in response to infection by a pathogen

Question 18

Why is it important for plants to defend themselves against pathogens?

Answer 18

Because they are at the start of most food chains, it is important for the plants and for other organisms.

Example damage to crops by pathogens can threaten human food security.

Question 19

How do phytoalexins work?

Answer 19

They are thought to disrupt the metabolism and cell structure of some species of fungi and bacteria.

Question 20

What is the most important part of the immune system?

Answer 20

The white blood cells, they travel around in your blood, patrolling for pathogens.

Question 21

How do white blood cells identify pathogens?

Answer 21

White blood cells have receptors in their membrane which help them to identify antigens on pathogens.

Question 22

What part of a cell identifies whether it is a pathogen or not?

Answer 22

Each cell has molecules on its surface called antigens. Each antigen is unique to the specific cell it is found on.

Question 23

Explain a plants physical defences against pathogens

Answer 23

Leaves have a waxy cuticle, which acts as a waterproof barrier.

Plant cells are surrounded by cellulose, this is a physical barrier against pathogens which have made it past the cuticle.

Question 24

Explain a plants immune system

Answer 24

If a pathogen crosses a plants physical defences, it detects it and responds by producing anti microbial substances as a form of chemical defence.

Question 25

What are phytoalexins?

Answer 25

Anti microbial substance produced in response to infection by a pathogen

Question 26

Why is it important for plants to defend themselves against pathogens?

Answer 26

Because they are at the start of most food chains, it is important for the plants and for other organisms.

Example damage to crops by pathogens can threaten human food security.

Question 27

How do phytoalexins work?

Answer 27

They are thought to disrupt the metabolism and cell structure of some species of fungi and bacteria.

Question 28

What is the most important part of the immune system?

Answer 28

The white blood cells, they travel around in your blood, patrolling for pathogens.

Question 29

How do white blood cells identify pathogens?

Answer 29

White blood cells have receptors in their membrane which help them to identify antigens on pathogens.

Question 30

What part of a cell identifying whether it is a pathogen or not?

Answer 30

Each cell has molecules on its surface called antigens. Each antigen is unique to the specific cell it is found on.