Viruses

Virus is like love. It can happen anytime to anyone.

Viruses

HIV

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Influenza

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Bacteriophage

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Cells

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Viral Reproduction

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Lytic Cycle

In the lytic cycle, viruses find a host cell to replicate themselves in. After making a lot of copies of it self, the virus will burst the cell open or weaken the cell wall with lyse and escape to find a new host cell to infect. The cycle continues with the each new copies infecting different cells.


E. coli is a virus that uses the lytic cycle.

Lysogenic Cycle

In this cycle, when a virus finds a host cell, they do not reproduce right away. Instead they mix with the host's DNA. The virus with reproduce with the host cell's DNA. So the virus is spread into its offspring. Some viruses could switch to the lytic cycle.


HIV is an example of a virus that uses the lysogenic cycle.

Characteristics of Life

What are the Characteristics of Life?


1. Reproduction: Make new organisms. (Sexual or Asexual)

2. Genetic Material: Molecule passed through reproduction.

3. Contains one or more cell: Collection of living matter.

4. Growth and Development: Increases in size and changes over the course of time.

5. Metabolism: Requires matter and energy to function.

6. Response to Stimuli: Reacts to changes in the environment.

7. Homeostasis: Maintains an internal balance.

8. Evolution: Changes in the related group of organisms.



Which ones do viruses have?


Viruses have the characteristics of:

- Genetic Material: They have DNA or RNA in them.

- Shape and Size: They have a specific shape and size.


Viruses do not have the characteristics of:

- Reproduction: They can only do this by infecting a living cell.

- Response to Stimuli: Viruses don't respond to the changes around them.

- Homeostasis: They don't have a way to control their internal conditions.

- Metabolism: They are too simple to collect and use their own energy.

- Growth and Development: They do not grow or develop over a course of time.

- Evolution: Viruses don't need to adapt over time. They don't respond to changes around them.

Questions

1. Describe the typical structure of a virus. What is a virus made of? What biomolecules would you find in a virus?


  • There are two biomolecules that can be found in a virus, nucleic acid and protein. A virus is made of either DNA or RNA, surrounded by a capsid which is made up of protein. The capsid is sometimes surrounded by a spiky coat called an envelope.They use this to latch onto host cells.
  • Some structures of the virus are icosahedral, enveloped, complex, and helical. A virus is called a virion when it reaches its complete form.



2. Discuss the different ways viruses gain entry into a cell.


  • There are different ways a virus could enter a cell. One way is endocytosis, a process where the host’s membrane surrounds the virus to form a vesicle. The envelope of the virus fuses with the membrane and the capsid protein is released. The the capsid protein is removed and the nucleic acid of the virus is released. A virus with no envelope could enter a cell with the same method.
  • Another way is when the envelope of the virus fuses with the membrane of the host and the nucleocapsid is released to the cytoplasm. Then the nucleic acid separates from its protein coat.



3. Explain why the Ebola virus would not infect a tobacco plant.


  • In a recent scientific search to find a cure for Ebola, scientists have discovered that the secret might be held in tobacco leaves. A genetically engineered virus was injected into the plant. The plant made antibodies.



4. Name five viruses and the type of cell that they attack.


  • Canine parvovirus attacks animal cells affects Canines (Dogs)

  • Equine herpesvirus 1 attacks animal cells and affects Horses

  • Tomato yellow leaf curl virus attacks plant cells and affects tomatoes.

  • Influenza A virus attacks animal cells and affects birds and some mammals.

  • Barmah Forest virus attacks animal cells and affects humans.



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.


  • A virus is not a living organism. It cannot be killed with antibiotics. Antibiotics kill off living organisms that cause harm, like some bacteria. The flu, however, is a virus. Taking antibiotics may cause more harm than good. It could increase the risk of getting an infection that could resist antibiotic treatment.



6. How is it that a person can be infected with a virus such as HIV and not exhibit symptoms?


  • HIV uses the lysogenic cycle, so the virus will silently replicates itself inside the person without them knowing. Later, when the lysogenic cycle turns into the lytic cycle, the person will start to exhibit symptoms of HIV. So years could go by without the person knowing he has HIV.