10. Pathogens and immunity

Question 1

A pathogen is?

Answer 1

a disease-causing organism.

Question 2

transmissible diseases?

Answer 2

Pathogens are passed on from one host to another and therefore the diseases they cause are known as transmissible diseases

Question 3

Pathogens can be passed on from host to host by?

Answer 3

Direct contact – the pathogen is passed directly from one host to another by transfer of body fluids such as blood or semen (eg HIV, gonorrhoea, hepatitis B & C) Indirect contact – the pathogen leaves the host and is carried in some way to another, uninfected individual

Question 4

Give 5 ways diseases can be spread

Answer 4

EDDDE! - Droplet infection - Eating contaminated food - Drinking contaminated water - Direct contact - Entry through wounds

Question 5

3 main ways in which the body defends itself against disease

Answer 5

MCC 1. Mechanical barriers 2. Chemical barriers 3. Cells

Question 6

Mechanical barriers

Answer 6

Mechanical barriers – structures that make it difficult for pathogens to get past them and into the body a) Skin – covers almost all parts of your body to prevent infection from pathogens. b) Hairs in the nose – these make it difficult for pathogens to get past them further up the nose so they are not inhaled into the lungs

Question 7

2. Chemical barriers

Answer 7

substances produced by the body cells that trap / kill pathogens before they can get further into the body and cause disease a) Mucus – made in various places in the body, pathogens get trapped in the mucus and can then be removed from the body (by coughing, blowing the nose, swallowing etc) b) Stomach acid – contains hydrochloric acid which is strong enough to kill any pathogens that have been caught in mucus in the airways and then swallowed or have been consumed in food or water

Question 8

Cells

Answer 8

different types of white blood cell work to prevent pathogens reaching areas of the body they can replicate in a) By phagocytosis – engulfing and digesting pathogenic cells b) By producing antibodies – which clump pathogenic cells together so they can’t move as easily (known as agglutination) and releasing chemicals that signal to other cells that they must be destroyed

Question 9

antigens?

Answer 9

All cells have proteins and other substances projecting from their cell membrane. These are known as antigens and are specific to that type of cell.

Question 10

antibodies?

Answer 10

An antibody is a chemical made by lymphocytes that is complementary to an antigen and, when attached, clumps them together and signals the cells they are on for destruction.

Question 11

agglutination?

Answer 11

The antibodies attach to the antigens and cause agglutination (clumping together). This means the pathogenic cells cannot move very easily.

Question 12

memory cells?

Answer 12

Lymphocytes that have made antibodies for a specific pathogen for the first time will then make ‘memory cells’ that retain the instructions for making those specific antibodies for that type of pathogen.

Question 13

Active immunity?

Answer 13

Making antibodies and developing memory cells for future response to infection is known as active immunity. There are two ways in which this active immune response happens: The body has become infected with a pathogen and so the lymphocytes go through the process of making antibodies specific to that pathogen Vaccination Active immunity is slow acting and provides long-lasting immunity

Question 14

Passive immunity?

Answer 14

This is when ready-made antibodies, from another source, are introduced to the body. Passive immunity is a fast-acting, short-term defence against a pathogen by antibodies acquired from another individual, eg: From mother to infant via breast milk, Injected antibodies for certain diseases where the individual is already infected and a fast response is required, like rabies or tetanus

Question 15

antibiotic?

Answer 15

An antibiotic is a drug that slows down or stops the growth of bacteria

Question 16

Antigens and antibodies (pictures)

Answer 16