10 disease and immunity

Question 1

Pathogens

Answer 1

Microorganisms that cause disease.

Question 2

Host

Answer 2

An organism that contains foreign DNA or a pathogen.

Question 3

Bacteria

Answer 3

Small, single-celled organism with no nucleus (plural: bacterium).

Question 4

Fungi

Answer 4

A group of organisms that includes moulds, yeasts and mushrooms.

Question 5

Protocists

Answer 5

Protoctists are mostly unicellular (and sometimes multicellular) organisms that have cells with a nucleus.

Question 6

Viruses

Answer 6

Microscopic particle consisting of genetic material surrounded by a protein coat.

Question 7

Transmissible diseases

Answer 7

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

Question 8

Some transmissible diseases and their pathogens

Answer 8

Disease Type of pathogen
cholera bacterium
athlete’s foot fungus
malaria protoctist
common cold virus

Question 9

Pathogens can be transmitted from an infected person to an uninfected person by:

Answer 9

Direct contact through body fluids such as blood

Indirect contact, such as from the air, through water or food, contaminated surfaces or animals.

Question 10

The first line of defence

Answer 10

The body’s initial defence against disease: non-specific physical or mechnical barriers that prevent pathogens from entering the body.

Question 11

Immune system

Answer 11

Organ system, tissues and cells involved in protecting the body against infection by pathogens.

Question 12

Second line of defence

Answer 12

The immune system is the second line of defence if a pathogen passes the first line of defence, enters the body and causes an infection. White blood cells, phagocytes and lymphocytes, detect and destroy pathogens.

Question 13

Mechanical barriers

Answer 13

Barriers that prevent the entry of pathogens into the body.

Question 14

Chemical barriers

Answer 14

Barriers in the body that trap and kill pathogens.

Question 15

White blood cells and how they work

Answer 15

A plasmid containing a foreign gene or sequence of DNA.
Depending upon the type of white blood cell, they can:

Surround and engulf a pathogen (phagocytosis) then destroy it
Produce antibodies, proteins which attach to pathogens and so mark them for destruction.

Question 16

The spread of disease can be controlled by preventing pathogens being transmitted to uninfected individuals. This involves:

Answer 16

A clean water supply
Good personal hygiene
Hygienic food preparation
Proper waste disposal
Treatment of sewage.

Question 17

Active immunity

Answer 17

Immunity that develops in response to a pathogen and involves the activation of memory cells.

Question 18

Antigens

Answer 18

Substances that trigger the immune response and cause the production of antibodies.

Question 19

Lymphocytes

Answer 19

Type of white blood cells that produce antibodies.

Question 20

Antibody

Answer 20

Antibodies are proteins produced by lymphocytes (a type of white blood cell).

An antibody for a particular antigen has a shape that fits, or is complementary to, the shape of that antigen.

This means the antibody can attach to an antigen on the surface of the pathogen.

Once it is attached to an antigen, the antibody can:
mark the pathogen for phagocytosis and destruction by phagocytes, or
cause the pathogen to break open and die (direct destruction)

Question 21

Once it is attached to an antigen, the antibody can:

Answer 21

Mark the pathogen for phagocytosis and destruction by phagocytes, or
Cause the pathogen to break open and die (direct destruction).

Question 22

Memory cell

Answer 22

A cell that forms from a lymphocyte as the immune system responds to an infection. It remains in the bloodstream and can recognise pathogens that infect after a first infection. It then differentiates to form antibody-producing lymphocytes that mount a secondary response.

Question 23

How vaccines work

Answer 23

A vaccine contains small amounts of material from the pathogen, or dead or weakened pathogens that cannot cause disease. The vaccine is introduced into the body

Lymphocytes in the immune system mount a primary response to the antigens from the pathogen. They make antibodies to target these antigens, and they also produce memory cells. These memory cells remain in the blood after the pathogen has been destroyed.

If a vaccinated person is infected by the live pathogen, the memory cells will recognise it very quickly. A secondary immune response is mounted, which destroys the pathogen, often before symptoms develop.

Question 24

Immunisation programmes

Answer 24

Young children may receive vaccinations against a wide range of infections, including measles, mumps, rubella, whooping cough, diphtheria and polio.

Teenage girls may be vaccinated against HPV (human papilloma virus) to protect against cervical cancer.

Question 25

Passive immunity

Answer 25

Immunity is gained when antibodies are transferred to the body from another individual, such as from a mother to her baby.
Memory cells are not produced in passive immunity.
The protection usually lasts only a few weeks or months, but
Protection happens immediately because the antibodies recognise the pathogen straightaway, which leads to their destruction.

Question 26

Natural immunity

Answer 26

Natural immunity happens after you get infected by a germ and your immune system responds by making antibodies to it.

Question 27

Artificial immunity

Answer 27

Artificial immunity is a mean by which the body is given immunity to a disease by intentional exposure to small quantities of it

Question 28

Cholera

Answer 28

Bacterial infection caused by water or food contaminated with the bacterium Vibrio cholerae.

Question 29

Toxin

Answer 29

A substance that can cause injury or death when in the body.

Question 30

Effect of the cholera toxin

Answer 30

Once the bacteria enter the body, they find their way to the small intestine.
(And yes, they survive the passage through the acidic stomach.)

Inside the small intestine, the bacteria start producing the cholera toxin.

The toxin causes the intestinal cells to secrete chloride ions into the lumen of the intestine.

The high concentration of chloride ions causes osmotic movement of large amounts of water into the intestinal lumen.

This in turn leads to watery diarrhoea, severe dehydration and loss of ions from the blood.