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

SMALLER
Viruses are ______________ than cells and
measured in _________________.
NANOMETERS

A nanometer is one billionth of a meter!
http://www.cellsalive.com/howbig.ht
m
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
Active Virus infects the cell immediately
a)_______________
Hidden Virus becomes part of the cell's
a)_______________
genetic material and remains silent for a while.
These types of viruses can become suddenly
active.
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