7A: Detecting Pathogens

Question 1

Pathogen

Answer 1

an agent or organism that causes disease

Question 2

Antigen

Answer 2

Any molecule that may trigger an immune response

Question 3

Types of Antigens

Answer 3

Self Antigens: a molecule from inside the body responsible for marking the cells of an organism as ‘self’ so the immune system doesn’t attack them

• Located on the surface of cells

Non-self Antigens: a molecule from outside the body that is recognised by the immune system and initiates an immune response in order to eliminate it

- Known as a foreign antigen
- E.g. A bacterium, donated organ
    - If an organ is donated to a person, that person must routinely take immunosuppressants in order to prevent the immune system from attacking the donated organ

Question 4

Major Histocompatibility Complex(MHC)

Answer 4

a group of proteins present on the surface of all self cells that enables the immune system to distinguish it from non self material

- Differ between individuals

- MHC I proteins are expressed on all nucleated cells in the body
- MHC II proteins are found on specialised cells of the immune system

Question 5

Malfunctions Involving Antigens

Answer 5

1. Autoimmune Disease: a disease in which an individuals immune system initiates an immune response against their own cells
   
   • Occurs when a malfunction involving antigens occurs
2. Allergen: a non-pathogenic antigen that triggers an allergic reaction

Question 6

Allergic Reaction

Answer 6

Allergic Reaction: an overreaction of the immune system to a non pathogenic antigen

Common Symptoms include:

- Itchy rash
- Runny nose
- Sneezing
- Shortness of breath
    - swelling

Question 7

Categories of Pathogens

Answer 7

Cellular Pathogens: a pathogen that has a cellular structure and is a living organism

- E.g. Bacteria, fungi, protozoa, parasites

Non-Cellular Pathogens: a pathogen that does not have a cellular structure and is non living

- E.g. Viruses and prions

Question 8

Key Cellular Pathogens: Bacterium

Answer 8

• Are Unicellular prokaryotes
• Can Infect almost any part of the body
• Causes disease through the production of toxins and enzymes which either affect cell functions or causes cell death
• E.g. - Neisseria Meningitidis causing meningitis

Question 9

Key Cellular Pathogens: Fungi

Answer 9

• Are eukaryotic organisms
• Contain long branching filaments called Hyphae

Hyphae: branching filaments of a fungus which help absorb nutrients from the environment

E.g. Thrush, Ringworm

Question 10

Key Cellular Pathogens: Worms

Answer 10

• Are multicellular invertebrate parasites
• Develops through the egg, larval, adult stages
• Varies in length but can grow up to 55m in length

E.g. parasites(tapeworm)

Question 11

Key Cellular Pathogens: Protozoa

Answer 11

• Are single celled eukaryotes
• Can be free living or parasitic
• Some can inhibit nucleic acid synthesis, protein synthesis and various stages of cellular respiration
• E.g. Plasmodium causing malaria

Question 12

Key non-cellular Pathogens: Viruses

Answer 12

• Infectious agents composed of DNA or RNA in a protein coat
• Not able to reproduce independently and instead insert their genetic material into a hosts cell and use their cells to replicate
• cause damage through the lysis of cells, the formation of cancer by affecting gene expression and the overstimulation of the immune system
• E.g. Influenza causing the flu

Question 13

Key non-cellular Pathogens: Prions

Answer 13

• Abnormally folded proteins that upon contact, have the ability to induce normal proteins nearby to become misfolded
• They only occur in mammals and affect only the brain and other neural structures
• Currently the only known infectious agents that don’t contain nucleic acids
• E.g. Cruetzfeldt-Jakob disease