A Smore by Grant Shamblin
Characteristics of Life
All Living Organisms
Can evolve- Viruses can evolve and do so rapidly through mutations.
Metabolize- Viruses cannot metabolize, because they have no way of digesting/producing food.
Can reproduce- Viruses cannot reproduce because they have no cells. All cells come from pre-existing cells.
Can respire- Viruses cannot respire because they have no biological processes, and as a result do not need oxygen.
Can grow- Viruses do not grow because they have no processes that can generate more genetic material.
Respond to their environment- Viruses do respond to their environment because they latch on their corresponding cells and can be "killed" by antiviral drugs.
Maintain homeostasis- Viruses do not need to maintain homeostasis because they have no organic processes that need to be balanced.
1. Describe the typical structure of a virus. What is a virus made of? What biomolecules would you find in a virus?
Viruses are typically DNA/RNA segments bound in a layer of proteins called a capsid. They occasionally have a layer of lipid called an envelope. Therefore, you would find lipids, proteins, and nucleic acids.
2. Discuss the different ways viruses gain entry into a cell.
Viruses can gain entry into the cell by latching onto the cell membrane and injecting a segment of nucleic acid called a prophage. They can also gain entry by posing as a useful material and tricking the cell into letting the virus in. (Only viruses with lipid envelopes can do this.)
3. Explain why the Ebola virus would not infect a tobacco plant.
All viruses are specified as to what they infect. Therefore, a virus that infects a human couldn't infect a plant.
4. Name five viruses and the type of cell that they attack.
HIV- attacks T cells
Rabies- attacks neurons
Ebola- attacks fibroblasts
Influenza- targets epithelial (respiratory) cells
Herpes- attacks skin cells
5. You have been diagnosed with the flu. Explain why a doctor will not provide you with a prescription for antibiotics in order to cure your infection.
Viruses are not "alive", so antibiotics have no effect.
6. How is it that a person can be infected with a virus such as HIV and not exhibit symptoms?
HIV works using the lysogenic cycle, so it remains dormant for a long time before it escapes the host cell.
1. Adsorption/Attachment- The virus attaches to the cell membrane of the cell.
2. Entry- The prophage (genetic material) enters the cell.
3. Replication- The recipes encoded in the prophage mass produce viral parts.
4. Assembly- The parts are assembled into more viruses.
5. Release- The cell lyses (explodes) and the viruses go to other cells.
Bacteriophage lambda uses this cycle.
The Lysogenic Cycle
1. Attachment- The virus attaches to the cell membrane.
2. Entry- The virus sends in the prophage.
3. Cell Division- The prophage doesn't "activate" and the cell healthily divides mitotically.
4. Lytic Cycle- The prophage activates and the lytic cycle begins.
HIV uses this cycle.