Mr. Murray Science 8 · Web view-The viruses that infect bacteria are called Bacteriophages and they have two types of life cycles (or two parts to their life cycle). View Activity:

Name: Date:

Microbiology: VirusesLearning Outcomes:

1. Evaluate the evidence used to classify viruses as living or non-living

2. Evaluate the effects of viruses on human health

Text: 181 to 183, 200 to 203. *This is required reading.

Introduction to Viruses

-Viruses are not cells, so they are not placed in any of the kingdoms of living organisms.

-They are composed of a _________nucleic acids_____________ core of either DNA or

RNA, and a ______protein_________ coat called a capsid. They may have an envelope

composed of a membrane from their host combined with viral glycoprotein.

-Bacteriophages have a more complex structure. They attack bacteria cells. (p.182)

-Viruses are ________parasites_____________ on living cells. Viruses are specific to a

particular ____________host cell ______________.

-Viruses are very small. They are 2 to 0.2 micrometers in size. This is comparable to a large

protein molecule.

-Illustrated below are a few different viruses.

Biology 11: Viruses Page 1

*See some creative Virus artwork at the Met:

http://www.mymodernmet.com/profiles/blogs/luke-jerram-glass-microbiology

-The diagram below is of a typical influenza virus. It belongs to a type of viruses that

are surrounded by a membrane envelope.

-Label: RNA, protein coat, membranous envelope and glycoprotein spike.

-How do enveloped viruses get their envelopes? How are the envelopes useful?

-Virus coats itself in a portion of the host cell membrane or nuclear membrane when it

leaves the cell. Camouflage from host cells/immune system.

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Are Viruses Alive?

Comparison of Virus and Bacteria Traits

Characteristics of Life Bacteria Viruses

Possesses Nucleic Acid 1 1

Consists of a Cell 1 0 (No cell membrane or

organelles)

Metabolism 1 0

Respond to Stimuli 1 0

Multiply 1 (Usually independently) 1 (Must be inside a host cell)

Evolve 1 1

-Viruses have some of the properties of living organisms, but depend upon their host cells for

most functions. They are obligate parasites because:

-They can only replicate in a host cell.

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Viral Reproduction

-A virus can only replicate by using the enzymes, ATP, ribosomes and tRNA of its host. How

are these molecules useful?

-Enzymes: Proteins that speed up reactions

-ATP: Energy molecule (Adenosine Triphosphate)

-Ribosomes: Synthesize proteins

tRNA: Transfer RNA, moves amino acids to ribosomes.


-View Activity: Simplified Reproductive Cycle of a DNA Virus (10.18) from the text

website and use the information there to label the main steps of the life cycle of a virus on

the diagram below. You must also read text page 201 carefully.


Bacteriophage Life Cycles (Text 182)

-The viruses that infect bacteria are called

Bacteriophages and they have two types of life cycles

(or two parts to their life cycle).

View Activity: Phage T2 Reproductive cycle (10.1) on the

text website and use this to understand the bacteriophage

life cycle.


Retroviruses (Text 498 to 499)

-View Activity: Retroviruses(HIV) Reproductive cycle (10.20). Use the information

found here to describe what retroviruses are.

-Have RNA as nucleic acid.

-Use the host cell enzyme Reverse Transcriptase to produce DNA, which will then

produce new m RNA for protein synthesis.

-Which modern, devastating disease is caused by a retrovirus?

AIDS (Acute Immunodeficiency Syndrome)

-What is the virus called? HIV (Human Immunodeficiency Virus)

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-Review Processes of Science: What cause infections in AIDS patients? (10.20) from the

text website.

-Why do AIDS patients become infected with

other diseases so easily? (p.498)

–Immune system is compromised

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The History of AIDS (http://fohn.net/history-

of-aids/ )

-Read the quote from an article about the history of AIDS.

“While the origin of the AIDS epidemic has been clarified, an explanation for why the

epidemic arose in the mid-20th century, and not before, remains a matter of speculation."

Chimpanzees are frequently hunted for food, especially in West-Central Africa, and we

believe that HIV-1 was introduced into the human population through exposure to blood

during hunting and field dressing of these animals," says Hahn. She further believes that

while incidental transmissions of chimpanzee viruses to humans may have occurred


http://fohn.net/history-of-aids/

http://fohn.net/history-of-aids/

a) Tobacco Virus; b) Pea Mosaic Virus

throughout history, it was the socio-economic changes in post-World War II Africa that

provided the particular circumstances leading to the spread of HIV-1 and the

development of the AIDS epidemic. "Increasing urbanization, breakdown of traditional

lifestyles, population movements, civil unrest, and sexual promiscuity are all known to

increase the rates of sexually transmitted diseases and thus likely triggered the AIDS

pandemic," adds Hahn.

-Another type of animal disease caused by a virus is Mad Cow Disease. This disease is

caused by a type of virus called a prion, which is a misfolded protein that cases normal

proteins inside of brain cells to also misfold. In doing so, it causes the brain and spinal

cord to deteriorate and affects the cow’s behaviour and nervous system.

-Can you think of any other animal diseases caused by viruses?

-Ebola virus, West Nile, SARS

Plant Viruses and Viroids

Plants can also be affected by viruses. One type of plant

virus is called viroids:

-Viroids are small circular RNA molecules that use plant

cell enzymes to replicate themselves.

-Viroids cause errors in the system controlling plant growth.

*Complete the Development of Virology Lab to learn more

about plant viruses.


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Mr. Murray Science 8 · Web view-The viruses that infect bacteria are called Bacteriophages and they have two types of life cycles (or two parts to their life cycle). View Activity: