1. Chapter 18 Studying Viruses and Prokaryotes

2. Infections can be caused in several ways.

3. Viruses, bacteria, viroids, and prions can all cause infection.
Any disease-causing agent is called a pathogen.
1 nanometer (nm) = one billionth of a meter
100 nm
eukaryotics cells 10, ,000 nm
viroids nm
viruses nm
prokaryotics cells ,000 nm
prion 2-10 nm

4. Bacteria:
one-celled, no nucleus, prokaryotic
Viruses:
has DNA/RNA and protein coat
cannot reproduce on their own
smaller
Both:
Can cause infections
Respond to the environment
Have genes, can reproduce

5. Comparison of viruses, viroids, and prions
Virus: 50 – 200 nm
Made of a protein coat (capsid) and genetic material
Viroid: 5 – 150 nm
Made of a single-stranded RNA molecule, NO protein coat
Causes plant diseases (stunts growth)
Prion: 2 – 10 nm
Made of a misfolded protein
Causes diseases of the brain (ex- Mad Cow)

6. Viroids – pieces of RNA

7. A prion is made only of proteins.
causes misfolding of other proteins
results in diseases of the brain

8. Mad Cow disease causes holes in brain tissue.

9. VIRUSES

10. What is a virus?
A virus is a submicroscopic infectious particle composed of a protein coat (capsid) and a nucleic acid core.
Viruses are similar in size to a large protein macromolecule, generally smaller than 200 nm in diameter.

12. Viruses are not considered living because they
Need a host cell to reproduce
Have no metabolism

13. Tree of Life

14. No links to other
forms of life.

15. Viruses are classified by:
the type of nucleic acid they contain
- DNA, RNA, RNA retroviruses
the shape of their protein capsule
- helical, polyhedral, enveloped

18. polyhedral (foot-and-mouth enveloped (influenza)
Different shapes of viruses
polyhedral (foot-and-mouth
disease)
enveloped (influenza)
helical (rabies)
capsid
nucleic acid
lipid envelope
surface proteins
capsid
surface proteins
nucleic acid
capsid
nucleic acid
lipid envelope
Surface proteins

19. Helical Viruses ex - rabies

20. Polyhedral shaped cold viruses, foot and mouth disease viruses

21. Enveloped ex – flu virus
Three parts:
Capsid
Genetic material
Lipid envelope
nucleic acid
capsid
lipid envelope

22. Bacteriophages – attack bacteria
They have
tails and spikes to attach
to the host cells. The tail
releases enzymes.

23. bacteriophages pierce host cells
colored SEM; magnifications:
large photo 25,000; inset 38,000x

24. Retroviruses RNA viruses that take their RNA and use the host
cell’s enzymes to make viral DNA.

25. Retroviruses go backwards… RNA to DNA then to proteins

26. Viruses identify their hosts by receptors (surface proteins)

27. How do viruses enter eukaryotic host cells?
By endocytosis
Fuse with the cell membrane (HIV)

28. How viruses replicate

29. In the lytic cycle, the virus destroys the host cell.

30. In the lysogenic cycle, viral DNA becomes part of the host cell’s DNA.
PROPHAGE – name of incorporated viral DNA.

31. Viral Reproduction Both: Cause infections Enter cell/ disrupt DNA
Both use host cell’s
materials
Viral Reproduction

33. How viruses get into the body
Cuts and scrapes
Body opening and mucous membranes
Viruses trick cells into letting them in by using their surface proteins
Antibiotics are not effective against viruses!

34. Viral Treatment???
Difficult since viruses mutate, particularly their surface proteins can be altered
Hybrid Medical Animation | Animation | Antigenic Shift - the Spread of a New, Mutated Virus
HIV virus destroys white blood cells used in immunity!

35. How do vaccines work?
Stimulate the body to produce antibodies (proteins that attack foreign invaders).

36. First viral vaccine
Edward Jenner made a vaccine against small pox using cow pox.

37. Jonas Salk made a vaccine against polio
He killed the polio virus with formaldehyde when he made the vaccine.

38. Vaccines stimulate the body’s immune system and it “remembers” the pathogen when encounted again.

40. Viral Diseases
Chicken pox
mumps
WEST NILE

41. 1918 Flu Epidemic

42. H1N1 Swine Flu

43. Ebola Virus

44. And now….the Zika virus
shorter

45. Will they take us out?

46. Virus Modeling