B3 - Infection and Response

Pathogen

A microorganism that causes disease: bacteria, virus, fungi, protist

Virus

Reproduces by inserting genes into cells which causes them to produce more copies

Examples of viruses

Rash (spread by droplets)

HIV (an STD that causes AIDS - compromised immune system)

Bacteria

Releases toxins into the body that damage cells

Examples of bacteria

Salmonella (undercooked food)

Gonorrohoea (STD, causes yellow discharge)

Fungi

Damage Cells

Examples of fungal diseases

Athletes foot

Rose black spot (causes leaves to fall off)

Protists

Single celled organisms

Examples of protists

Malaria (caused by a protist that infects red blood cells, mosquitoes are the vector)

What defences do humans have against pathogens?

Skin (barrier) , mucus (traps) , acids/enzymes (kill)

What defences do plants have against pathogens?

Cell wall, waxy cuticle, bark (barriers), antibacterial chemicals, poison / thorns (deter)

What is a lymphocyte?

A type of white blood cell

How do lymphocytes help prevent illness?

Produce antitoxins to neutralise toxins made by pathogens and antibodies that bind to the antigen of a pathogen (but only if they fit). These stop viruses from infecting cells and causes them to clump together. Once the correct antibody is found, t-cells store it in your lymph nodes ready for the next time (immunity)

Phagocyte

Another type of white blood cell that ingests pathogens once neutralised by antibodies

Vaccine

Introduces a dead/inert version of a virus into your body to gain immunity without becoming ill

What do antibiotics kill?

Bacteria

What is a disadvantage of antibiotics?

Hard to make them target specific bacteria, and not damage our cells, or other ‘good’ bacteria

Where does aspirin come from?

Trees

Where does penicillin come from?

Mould

What is a disadvantage of producing synthetic drugs?

Cost a lot of money to produce

When drugs are put through trials, what are they assessed for?

Efficacy, toxicity and dose

What are drugs tested on?

Cell tissue, then animals, then humans

Blind trial

Test group are given drug, control group are given placebo, without being made aware 

Double blind trial

Doctors don’t know who has been given the placebo, to eliminate bias