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.

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Infection Cycles

Lytic Cycle

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.