VIRUSES AND BACTERIA
Composed of a nucleic acid with a protein coat◦ What’s a nucleic acid???◦ Protein coat is called a capsid
NOT ALIVE◦ Not made of cells◦ Don’t grow◦ Don’t reproduce by themselves◦ Don’t use energy
◦ Can be dormant for hundreds of years
Nucleic acid has instructions for making more virus◦ Range in size◦ Some have 4 genes, some have hundreds
Protein arrangement determines the shape
What are the 2 parts of a virus? What are the two nucleic acids? Give one reason why viruses are not ALIVE
(there are 4) What is a capsid? Why can’t you “kill” a virus?
Replicate using a host cell What does replicate mean?
Bacteriophage = virus that infects a bacteria◦ they can infect bacteria IN YOUR BODY!!!
Some viruses are specific and infect only certain cells or species◦ Example: tobacco mosaic virus◦ Others infect a variety of cells and species
Example: influenza
Replication
◦ Viral DNA or RNA takes over cell’s metabolism
◦ Viral genome hijacks cell into making parts for itself
◦ Cell fills up with viruses and bursts open
Flu Attack video
How do viruses replicate? What is a bacteriophage?
Retroviruses◦ RNA-containing virus gets into cells◦ Virus uses reverse-transcriptase (an enzyme) to
reverse-engineer DNA from its RNA◦ DNA is integrated into host cell’s chromosome
Presence of reverse-transcriptase in a person is evidence that they have a retrovirus
Common retrovirus: HIV
If not alive—where did they come from?◦ Ancestral form of life?
NO—they can’t reproduce w/o host cell
◦ Originated from host cell? maybe Piece of nucleic acid that broke free Stayed inside cell with ability to reproduce
parasitically
◦ From outer space??
Name one common retrovirus What enzyme makes viral DNA using its
RNA?
ARE ALIVE – microorganisms◦ Made of cells◦ Reproduce by themselves◦ Grow and use energy
Single-celled
Not all are harmful! Most are good!◦ Cheese, yogurt, beer…◦ E. coli in your intestines◦ Etc.
No nucleus or organelles (prokaryotic)
Consist of one cell surrounded by a cell wall◦ Wall is different from that found in plant cells
May also have a capsule surrounding cell wall◦ Bacteria with a capsule are more likely to cause
disease
Often have flagella or cilia for movement
◦ Some secrete toxins as part of their metabolism
Examples of pathogenic bacteria:◦ Strep throat◦ Tetanus◦ Pneumonia
Prevention and treatment of infections◦ Antibiotics: attack and kill bacteria
Antibiotic-resistant bacteria
◦ Antitoxin Botulism
◦ Sterilization: cleaning wound/implements
◦ Vaccination: injecting heat-killed bacteria so person will make antibodies
What is significant about a bacterium with a capsule?
Give one method of killing or preventing bacterial infections (there are 4)
How do you treat/prevent viruses?◦ Vaccination – prevents
◦ To “kill”: Bleach Ultraviolet light Heat That’s it…no medicines…
Viruses are ALL PATHOGENIC
What is the only way to prevent viral infections?
Give one method of “killing” viruses (there are 3)
Give one way bacteria and viruses are different
Scale of the Universe
Top 5 Deadliest Diseases