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