Chapter 10: Disease and Immunity

Question 1

Name the three types of Pathogens that cause diseases.

Answer 1

• Bacteria.
• Viruses
• Protoctists

Question 2

Define Pathogen.

Answer 2

A disease causing organism.

Question 3

Define Transmissible diseases.

Answer 3

A disease in which the pathogen can be passed from one host to another.

Question 4

Name the two ways by which pathogens can be transmitted

Answer 4

• Direct contact
• Indirect contact

Question 5

Name the three ways in which your body limits the entry of pathogens.

Answer 5

• Mechanical barriers.
• Chemical barriers.
• White blood cells.

Question 6

Describe the two most important mechanical defenses of your body.

Answer 6

• skin: is a tough impenetrable barrier that most pathogens cannot get through.
• Hairs in the nose: Helps to stop dust particles containing pathogens from getting down into the lungs.

Question 7

Describe the two most important chemical defenses of your body.

Answer 7

• Stomach hydrochloric acid: kills bacteria present in food we eat or water we drink.
• Mucus in the trachea: helps to trap dirt and dust particles containing pathogens from reaching the lungs.

Question 8

What is white blood cells used for in limiting the ability of pathogens entering the body.

Answer 8

they use phagocytosis and antibodies to destroy pathogens once they are inside the body.

Question 9

What is the main method to prevent the spread of transmissible diseases?

Answer 9

Vaccination

Question 10

Describe the process of vaccination.

Answer 10

• Vaccination inserts a weakened pathogen, or its antigens,into your body.
• the antigens stimulate an immune response by lymphocytes which produce antibodies
• memory cells are produced that give long term immunity

Question 11

How does vaccination reduce the risk of a disease spreading?

Answer 11

It reduces he number of people in whom the pathogen can breed, so it reduces the chance of unvaccinated people getting the disease.

Question 12

Describe three methods of maintaining good food hygiene to reduce the chance of pathogens entering the body.

Answer 12

• keep hands,tools and work surfaces clean so that they do not transfer pathogens to the food.
• Do not allow food to remain warm for long periods of time. Either keep it cold, to reduce the chance of a pathogen growing, or keep it very hot, to kill the pathogen.
• Keep cooked meat away from raw meat so that no bacteria can be transferred from the raw meat.

Question 13

Describe two methods of maintaining good personal hygiene to reduce the chance of pathogens entering the body.

Answer 13

• wash your hands frequently;do not put your hand in your mouth unless you have cleaned them. Be careful to wash your hands after using the toilet to avoid spread of pathogens from feaces.
• Do not cough or sneeze into the air or over another person.

Question 14

In what ways can careful waste disposal prevent spreading of diseases?

Answer 14

• covering bins to prevent access to flies and rats.

- Ensure all waste is disposed in proper landfill sites, where it will be properly covered in soil.

Question 15

Why is proper sewage treatment important.

Answer 15

it reduces the chance of pathogens entering water bodies,in which people may later swim, or where they may drink the water. Raw sewage should not be allowed to flow into rivers or the sea.

Question 16

What are antibodies

Answer 16

Proteins that bind to antigens leading to direct destruction of pathogens or marking of pathogens for destruction by phagocytes

Question 17

When are antibodies produced.

Answer 17

When a lymphocyte comes into contact with its specific antigen, antibodies is produced.

Question 18

What is an antigen?

Answer 18

it is a molecule that is foreign to your body. It may be on the surface of the cell membrane of a pathogen or can be in the toxins released by a pathogen and is circulating around the blood.

Question 19

Why is each antibody specific to an antibody?

Answer 19

Each antibody has specifically shaped binding site which has a complimentary shape to the binding site of the antigen with which it can bind.

Question 20

What do antibodies do when they come into contact with an antigen?

Answer 20

They either:

• directly destroy the antigen , or the pathogen tow which the antibody belongs. or
• marks the antigen, so that phagocytes can come and destroy it by phagocytosis.

Question 21

What is meant by the term active immunity?

Answer 21

it is the defense against a pathogen by the production of antibodies in the body.

Question 22

Describe the process of active immunity. [7]

Answer 22

• The lymphocyte encounters the specific antigen.
• The lymphocyte divides over and over again to form clones just like itself.
• Meanwhile, the pathogen breeds and makes you ill.
• Eventually if enough antibodies are made, the pathogen is destroyed and you get better.
• some of the lymphocytes remain as memory cells.
• When the pathogen enters again, these memory cells help antibodies to be made and the pathogen is destroyed before you become ill.
• This is immunity.

Question 23

Explain why you get ill even though you have the correct lymphocyte in your immune system.

Answer 23

Lymphocytes have to form clones of themselves and this takes time, allowing for the pathogen to breed and make you ill. However, when sufficient antibodies are produced the pathogen is killed and you get better.

Question 24

Explain why it is unlikely to get a disease again, after a person has recovered from the disease previously.

Answer 24

• After the first recovery, some of the lymphocytes remain as memory cells.
• when the pathogen enters again, they will be many cells that can produce the antibody against its antigens.
• The pathogen is therefore the pathogen is destroyed before it makes the person ill.

Question 25

Why does active immunity last for a long time.

Answer 25

Because memory cells have been produced.

Question 26

What is passive immunity?

Answer 26

is a short-term defense against a pathogen by antibodies acquired from another individual,for example mother to infant.

Question 27

How do young babies get anti-bodies through passive immunity.

Answer 27

Through breast-feeding from their mothers. It protects them from diseases in which their mothers have gained immunity to.

Question 28

Why do babies need antibodies from their mothers?

Answer 28

It takes time for a baby’s immune system to develop fully.

Question 29

Why does passive immunity not last very long?

Answer 29

Because memory cells have not been made.

Question 30

What is type I diabetes?

Answer 30

Is an illness which the cells that make insulin in the pancreas are destroyed.

Question 31

What causes Type I diabetes?

Answer 31

When the body’s own lymphocytes behaving as though the cells in the pancreas are foreign, and attacking them as though they carry foreign antigens.

Question 32

what is cholera

Answer 32

A disease caused by a bacterium which is transmitted in contaminated water

Question 33

What does cholera cause

Answer 33

Diarrhoea

Question 34

Where does cholera live and breath in?

Answer 34

In the small intestine

Question 35

How does cholera toxin cause diarrhoea

Answer 35

1.It produces a toxin that stimulates the cells lining the intestine to secrete chloride ions which accumulate in the lumen of the small intestine.
-this increases the concentration of the fluid in the lumen,lowering the water potential.
-then water moves out of the blood and into the lumen of the intestine by osmosis.

Question 36

How does lymphocytes respond to a pathogen

Answer 36

1-A lymphocyte comes into contact with antigens that fit the shape of the antibodies it can make
2-The lymphocyte divides to form many identical cells
3-The lymphocytes secrete antibodies
4-The antibodies bind to the antigens and destroy the pathogens.

Question 37

What is direct contract

Answer 37

When one person’s blood comes into act with another person’s blood during a transfusion.

Question 38

What is indirect contract

Answer 38

contaminated surfaces, animals and by breathing in air containing liquid droplets sneezed out by some one with a respiratory infection.