Take out your homework packet a pen or pencil and clear your desk.

1. Define the following terms - Virus A small nonliving particle that invades a living cell. Uses the host cell to reproduce Eventually kills the host cell.

1. Define the following terms -Parasite/Host Parasite – An organism that lives on or in a host. They usually cause harm to the host. Host – living organism that provides a source of energy or a suitable environment for the virus or parasite. Tick uses mammals as hosts Tapeworm – lives in the intestines of dogs and cats

Viruses act like parasites using the cell as the host organism

2. Viruses are considered to be nonliving because: a) Viruses are not cells. b) Viruses do not use energy to grow. c) Viruses cannot take in food or make food. d) Viruses cannot produce waste.

3. How are viruses similar to living organisms? They have the ability to multiply.

4. Besides humans, what are some other organisms that viruses can infect? Viruses can infect animals, plants, bacteria, fungi, and protists. Tobacco Mosaic Virus

5. When you are sick with a cold, are you the host or the parasite? The Host

6. How are viruses named? Ebola virus - named after the place in Africa where it was discovered. Polio – named after the disease it causes. Tomato mosaic virus – named after the organism it infects. Epstein-Barr – named after the scientist that discovered it.

7. Define Bacteriophage: Virus that infects bacteria. Means “bacteria eater”

8. List four different shapes of viruses a) round b) rod shaped c) brick-like d) thread-like e) bullet-like f)robot-like (bacteriophage)

9. Size of viruses Viruses are ______________ than cells and measured in _________________. A nanometer is one billionth of a meter! m SMALLER NANOMETERS

10 Label the part of the virus: Outer protein coat Genetic material The function of A:  Protection.  Aids in attaching to the host cell. Function of B:  contains the directions for making new viruses.

13. Why does a virus only invade a specific type of cell? Because the outer protein coat acts like a “lock-and-key” system which is very specific. Each virus will attach to only one or a few types of cells.

14. How do viruses multiply? The virus attaches and enters the cell. Once inside it takes over the functions of the cell and redirects it to make new virus parts. New viruses are assembled inside the cell. When the cell is full it bursts and releases the new viruses.

15. Two types of viruses a)_______________ infects the cell immediately a)_______________ becomes part of the cell's genetic material and remains silent for a while. These types of viruses can become suddenly active. Active Virus Hidden Virus

16. Give an example of a hidden virus. Cold sore

17. Most viruses are harmful but some are useful. Give an example of each: Harmful:  Any virus that makes us sick (cold, flu etc.)  Viruses that infect plants can kill farmer's crops  Viruses that infect animals can hurt pets Helpful:  Can be used for gene therapy in diseases such as cystic fibrosis