CIE IGCSE Biology Unit 10: Disease and immunity

pathogen

A disease causing organism

transmissible disease

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

Method of pathogen transmission

- blood or other body fluids

- contaminated surfaces or food, from animals, or from the air

Mechanical barriers

dead skin and hairs in the nose

Chemical barriers

mucus and stomach acid

Blood defences

phagocytosis and antibody production by white blood cells

Antigens

Chemical that stimulates lymphocytes to produce antibodies, have specific shapes, so specific antibodies which fit the specific shapes of the antigens are needed

Antibodies

lock on to antigens leading to direct destruction of pathogens, or marking of pathogens for destruction by phagocytes

Antitoxins

Antibodies that make toxins harmless

active immunity

defence against a pathogen by antibody production in the body, gained after an

infection by a pathogen, or by vaccination

memory cells

a long-lived lymphocyte capable of responding to a particular antigen on its reintroduction, long after the exposure that prompted its production.

process of vaccination

- harmless pathogen given which has

antigens

- antigens trigger an immune response by

lymphocytes which produce antibodies

- memory cells are produced that give

long-term immunity

role of vaccination in controlling the spread of diseases

Gives active immunity against a disease to large population and protect those who cannot get vaccines by decreasing the chances of coming into contact with the disease

passive immunity

short-term defence against a pathogen by antibodies acquired from another individual, e.g. mother to infant. Memory cells are not produced in passive immunity

Importance of passive immunity for breast-fed infants

Antibodies in breast milk protect the baby against diseases until it develops its own lymphocytes

autoimmune disease

a disease in which the immune system attacks the organism's own cells

Type 1 Diabetes

autoimmune disease caused by the immune system attacking and destroying pancreas cells that produce insulin

Insulin

Protein hormones that stimulates the liver and muscles to store glucose as glycogen.

Methods of preventing transmissible diseases

- personal hygiene

- hygienic food preparation

- proper waste disposal

- sewage treatment