Module 7

what are the accelular pathogens?

• viroids

• prions

• virus

describe viroids in terms of size, composition, & habitat

• Smallest pathogens known

• Composed of a short strand of circular, single-tranded RNA without a protein coat

• All inhabit higher plants (some are economically important)

• Composed of nucleic acid but do not code for any protein

describe prions in terms of its cause, composition, structure, & symptoms

• Cause brain disease in mammals

• Consist of abnormally folded prion protein

• Normal prion protein is found throughout the brain & spinal cord in humans & mammals

• Disease-causing prions induce abnormal folding patterns when coming into contact with other prion proteins 

• Symptoms:

  • Loss of motor control

  • Dementia 

  • Wasting & eventual death

  • At post mortem, all animals that die from prion diseases have large vacuoles in the brain

describe virus in terms of composition, what it is, size range, examples (+ define bacteriophage)

• Infectious agent made of nucleic acid (DNA or RNA) wrapped in a protein coat called a capsid

• Have no nucleus, organelles, cytoplasm, cell membrane, & are non-cellular

• Are parasites: an organism that depends entirely upon another living organism to live while harming that organism

• size range: nanometres

• E.g. flu (influenza), HIV, bacteriophage (viruses that infect bacteria, surrounded by capsid, contains RNA or DNA inside)

identify the shapes of viruses

• helical

• polyhedral (causes pink eye, pneumonia)

• spherical

• complex

what are viruses classified into?

1. Host cell type (they are host specific e.g. animal/plant/bacterial/fungal

2. Nucleus acid: DNA or RNA

3. Protein coat structure (shape/number)

how do viruses replicate?

• Only reproduce in host cells

• Once inside, nuclear material from the virus causes the cytoplasm to produce new viruses → kills host cell & new viruses escape from it

describe how the tobacco mosaic virus enters plant cells & transmits

• First virus discovered & purified

• Enters plant cells only through mechanical wounds which either temporarily opens the plasma membrane or allow pinocytosis

• Transmitted through direct contact between plants or soils

describe how adenovirus is transmitted & what it causes

• Receptor mediated endocytosis

• Transmitted by contact or faecal oral route

• Causes conjunctivitis

what are the cellular pathogens?

• bacteria

describe the composition of bacteria

• single celled

• prokaryotic

• cell wall

• cell membrane

• cytoplasm

• circular DNA (no true nucleus)

draw & label a bacterial cell

how does bacteria cause disease?

by producing toxic compounds (exotoxins) or releasing the substances when destroyed (endotoxins)

why is bacteria often the cause of food poisoning?

As toxins retain their destructive capacity beyond bacterial death, they are often the cause of food poisoning

what do bacteria do?

1. Enter person (host)

2. Reproduce in a host (require adequate temperature, pH, food & water)

3. When in host, produce enzymes which break down tissues

where is DNA contained in bacteria?

contained in chromosomal DNA

what forms the nucleoid in bacteria?

the chromosome, several protiens & RNA molecules

describe plasmid DNA

• small molecule within a cell

• physically separated from chromosomal DNA

• replicate independently

compare

describe tuberculosis: category, transmission, symptoms & effects

• Bacteria

• Airborne transmission → sneeze, cough, shout, speak, sing

• Symptoms & effects

  • Infects lungs, causing a persistent cough (sometimes blood), fever, & fatigue

  • Dangerous because it can survive inside immune cells (macrophages) & become latent (non-replicating) & anaerobic