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microscopic organisms (present in air, soil, water, food)


Differentiate between an infection and disease

An infection is when pathogenic bacteria enter the human body and multiply
A disease occurs only when cells or organs are damaged by the infection and visible symptoms arise
For this to happen pathogens must gain entry (cross the cellular boundary* to the internal environment of the body, overcome defence mechanisms, become established in one or more sites, and multiply rapidly


Incubation period

The incubation period of a disease is time taken (from initial entry) for pathogens to multiply to cause the first symptoms of a disease


How are infectious diseases spread

Direct transmission (kissing, sex), indirect transmission (sneeze, cough), contact/ingestion of contaminated objects, blood, vectors that carry and spread pathogens usually from animals to humans zoonotic disease)


How are non-infectious diseases spread

Cannot spread from infected people to healthy people via the environment, spread through environment (antigens in the environment, smoke, asbestos), nutritional deficiency (scurvy, deficient in vit C), inherited or hereditary


How do pathogens enter the body

Cuts/burn/punctures, nasopharynx, mouth (digestive tract), genital openings



Prokaryotic microbe that has double stranded DNA, reproduce every 20 minutes
Shape (cocci sphere, bacilli cylinder, spirochaetes swirly
Gram stain (+ thick peptidoglycan, - thin peptidoglycan and layer of LPS resistance to antibiotic)
Exotoxins are highly toxic soluble proteins produced by bacteria, damage plasma membrane, some block normal nerve function, Endotoxins are made from LPS, released only after bacteria die and outer membrane breaks down, chills fever weakness
Capsule (protects bacteria from macrophages, increasing virulence)
Oxygen requirements (obligate aerobes and anaerobes, facultative anaerobes, form spores that make bacteria resistant and inactive until favourable conditions return)



No metabolic activity, has genetic material ss or ds, DNA or RNA (surrounded by protein capsid) that encodes for proteins once within a host cell (can't reproduce independently, energy and machinery to replicate)

Called virion if in extracellular environment



Virions released until cell dies
Envelope is made from the plasma membrane when virus buds from host cell
Enveloped virus are easier to destroy and do not last long outside host cells



Host cell explodes, virions (naked virus) released into extracellular fluid to infect other cells



Infectious particles made of protein and lack nucleic acids
Prion proteins are most abundant in nerve cells
Contact from harmful protein can result in the unfolding and refolding (abnormally) to form harmful proteins
They accumulate into rods that form plaque in nerve cells, killing nerve cells, resulting in holes in the brain (spongiform)



Any molecule that initiates an immune response Encoded by a person's HLA (human leucocyte antigens) genes allowing for 'self-antigens' to be identified