BCLN BIOLOGY 11 – Rev July 2014

Unit 4 ~ Learning Guide Name: _______________

INSTRUCTIONS

Using a pencil, complete the following notes and questions as you work through the related lessons. You are required to have this package completed BEFORE you write your unit test. Do your best and ask questions about anything that you don't understand BEFORE you write the unit test.

4.1 NOTES: STRUCTURE OF VIRUSES

Discovery of the Virus

Many human epidemics were well documented and observed in history, but ________ __________________________. The following 3 discoveries shaped our knowledge of viruses and disease:

1. Jenner's Experiment (1700's).

______________________________________________________________. He discovered that milkmaids who contracted cowpox and recovered ________ ______________________________________________________________________________________________. On the 14 May 1796, a young milkmaid called Sarah Nelmes came to see him with blister like sores. _______________ ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ which he would inject later. To test his hypothesis Jenner approached a local farmer and explained that if his theory was correct, the man's son James would never contract smallpox. Surprisingly, the farmer agreed. Jenner made two small cuts on James's left arm. He then poured the liquid from Sarah's cowpox sores into the open wounds which he bandaged. James got sick with cowpox but once recovered and exposed to smallpox he did not become ill with the smallpox disease. This was an extremely risky experiment, but James lived and Jenner had found a way to prevent smallpox.

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Jenner called his idea "___________________________" from the word vaccinia which is Latin for cowpox. Jenner also introduced the term ______________________.

2. Tobacco Mosaic Virus (TMV)

______________________________ ______________________________. The virus caused a blotchiness on the leaves of tobacco crops making them unmarketable and worthless. Solving this problem was a priority as tobacco was an important crop in these times.A German scientist, Adolf Meyer, suggested that Mosaic disease was contagious and proposed that the infectious agent was an unusually small bacterium that could not be seen with a microscope. He tested his hypothesis by successfully transmitted the disease by spraying sap from infected plants onto the healthy ones. Using a microscope, he examined the sap and was unable to identify a microbe.

3. TMV Research Continued

In 1897 a Dutch microbiologist, Martinus Beijerinck _______________________ ___________________________________________________________________________________________________________________. He ruled out the theory that a filterable toxin such as bacteria caused the disease by demonstrating that the infectious agent in filtered sap could reproduce.

So what exactly is a Virus???

A virus is a ____________________________________________________________ ______________________________________________________________________.

Viruses _______________________________________________________ and because of this feature are considered _________________________. In fact, viruses are ____________________________________________________. Viruses affect all types of cells, __________________________________________________________

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____________________________________________. For example, bacteriophages ___________________________________________________, the tobacco mosaic virus infects only plants, and the rabies virus only infects mammals. Viruses can be even more specific than this. Some human viruses even specialize in specific tissue. Human immunodeficiency virus (HIV) affects specific types of white blood cells and the polio virus ________________________________________________. Viruses are so specific because the capsid binds with ______________________ in the host cell's plasma membrane. If the receptors do not match then the virus cannot attach. Once attached to a cell, the virus ___________________________ within the host cell for its own purposes.

Viruses and their relationship to host cells has led to the hypothesis that the _______________________________________________________________________________________________________________________________. This statement suggests that viruses evolved after cells developed. If so, this means that new viruses are developing all the time. New viruses can develop ___________________________ _____________________________________________. This means that antibodies produced by the body can work against one type of virus, but might not recognize the new mutated virus.

Virus Structure

There are _____________________________________ ________________________________ to viruses:

1. Proteins forms a structure called the coat or _______________. The capsid acts as the protective covering for the nucleic acid it contains. The proteins in the virus’ capsid must match the protein markers on the surface of the membrane of the cell it is trying to invade. As previously stated this feature is responsible for viral specificity.

2. Nucleic acids - All viruses contain either DNA or RNA, ___________________________________. This means that instead of using DNA to control the activities of the host cell

_____________________________________________________________________________________________________ which can then direct the activities of the host cell to reproduce viral particles.

There are many different shapes and types of viruses but, because of the

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similarities between bacteriophages and animal cell viruses, the bacteriophage can be viewed as a model for animal cell viruses. The diagram above is of a typical bacteriophage.

Head Region - _______________________________________________

The Tail - includes the plug, a ___________________________________ _____________________________________________, and the ___________ _______________________________________________ to a bacterial host cell.

Viral Replication

________________ do not reproduce, they ___________________________________ ____________________________________________________________. Host cells ___________________________________________________________________________________________________________. Viruses are specific to a particular host cell because part of the capsid binds to the receptor on the host cell's plasma membrane in a lock and key fashion. The virus then will inject its viral nucleic acid into the host cell and _________________________________________________________________ ____________________________________________________________________.

Replication of Bacteriophages

Bacteriophages are viruses that are parasitic to bacteria. These phages must use bacteria to replicate. Phages have two types of cycles. In ______________________ _____________________ the virus is replicated within the host cell resulting in ______________________________________________________________ _________ releasing all of the newly formed virus particles. In the _________________________________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ sometime in the future.

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Reproductive Cycles

1. Lytic Cycle

There are five key stages to the lytic cycle: i. __________________________ - capsid combines with the bacteria's

receptor in a lock and key fashionii. __________________________ - enzymes from the virus start to eat

away the bacterial cell wall and will inject its viral DNA into the bacterial cell.

iii. __________________________ - at this stage the virus inactivates the bacterial genes and takes over the metabolic functions to produce copies of DNA and produce the capsid.

iv. __________________________ - during this stage, the viral DNA and capsids are put together.

v. __________________________ - lysosomes are made and produce hydrolytic enzymes to eat a hole in the cell wall of the bacteria. At this time, the cell will lyse and the newly formed viruses will leave the host cell.

2. Lysogenic Cycle

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________________________________________________________________ ______________________________, the ______________________________ _________________________________________________, but ___________ _______________________________________________________. During the lysogenic cycle, the phage becomes a prophage that is integrated into the host genome (DNA). At a later time, the phage may start the lytic cycle. When a virus is latent (i.e., __________________________) it is called a prophage. ________ ______________________________________________________________________________________________________________________________________________________________________________.

Examples of lysogenic viruses: Herpes, Hepatitis, HIV

YOU SHOULD WATCH THE LYTIC AND THE LYSOGENIC CYCLEVIDEOS BEFORE PROCEEDING ANY FURTHER!

Retroviruses

Retroviruses are viruses that have the __________________________________, _____________. These viruses contains an enzyme called _____________________ ___________________________________. This enzyme ________________________ _____________________________________________ (in other words, it allows the RNA to make DNA). __________________________________________________ __________________________________________, which can hide in the host's DNA. __________________________________________________________________________________________________________________________________________________________________________________. An example of a retrovirus is HIV and some that cause cancers.

Are Viruses Alive?

What are the characteristics of life? How do we define whether something is living or not? Living things….

1. ___________________________________________________.2. ___________________________________________________.3. Require a constant energy supply.4. ___________________________.5. ____________________________________.6. ______________________________________________.

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7. Contain enzymes.8. Can move.

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So, are viruses living or nonliving? The following table gives evidence to support each theory.

Living Non-living

Viruses have DNA or RNA and protein.No non-living thing carries nucleic acid.

______________________________________________________________________

_____________________________(slightly different variations)

Viruses do not eat

Viruses display continuity Viruses do not grow

Viruses have the ability to reproducein that one generation follows another

______________________________________________________________________

Viruses contain enzymes Viruses do not reproduce on their own. Viruses are parasitic

Viruses do not move

Viruses ____________________________________________ things as they do not exhibit many of the characteristics of life.

Viruses are not classified in the classification system because they are _______________________________________ and should not be classified with organisms that are cellular. Viruses are generally smaller than 200 nm in diameter and can be crystalized.

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4.1 PRACTICE: STRUCTURE OF VIRUSES

1. Viruses are ______________________________________________ parasites that invade living cells. (1 mark)

2. The type of virus that only invade and infects bacteria are called ________________________________________. (1 mark)

3. Evidence that viruses may have come from living cells is the fact that viruses' nucleic acids are similar to the host cells' _____________________. (1 mark)

4. Each virus type is _______________________________ to the type of tissue cells that it invades. (1 mark)

5. Antibodies from last year's flu shot do not work because viruses have the ability to _____________________________. (1 mark)

6. Viruses are very specific to particular cells because the protein portion called the capsid binds to the receptor on the host's cell in a ________________________ manner. (1 mark)

7. After the nucleic acid of the virus enters the cell, it takes over the _____________________________ activity of the cell so that more viruses can be produced. (1 mark)

8. In the lytic cycle, the host cell must go under ______________________ to release new viruses. (1 mark)

9. In the ________________________________ cycle, the virus does not immediately replicate. Replication will take place some time in the future. (1 mark)

10.When the phage is not actively replicating, this means that it is _______________________________. (1 mark)

11.The viral DNA now, now called a __________________________________, binds with the bacterial DNA and is replicated together. (1 mark)

12.________________________________________ factors can induce the lysogenic cycle to enter the lytic cycle. (1 mark)

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13. Please label and describe the function of the following viral structures on the diagram below. Please be neat. (12 marks)

o capsid o nucleic acido head o tailo tail fibers o plug

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4.2 NOTES: VIRAL DISEASES

Viral Diseases

We now know that viruses are considered pathogens that cause disease. We know that many of these diseases are specific to a particular type of host cell and that viruses are not considered living as they require this host cell to reproduce. We also know that viruses cause a large variety of diseases.

Some ________________________________________________ while ____________ ___________________________________________________________________________________________________________________________________________________________________________________________________________. Some new antiviral medications are being developed but are only used in special circumstances at this time.

Viral pathogens are newsworthy. You may recognize the ones in the list below. You will notice that there is a lot of variety in the structure and function of these viruses. This variety is not a surprise as viruses have been evolving for a very long time along with the cells they infect.

The side photo is a micrograph of an Adenovirus that causes the common cold. You know the symptoms.

Photos below are of Smallpox which causes high fever and the formation of small blisters on the skin. ______________________________________________________ _____________________________________________________________ (1970's). Let's hope it stays that way as vaccinations ceased in the 1980's.

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Photos below are of the Polio virus which is transmitted through direct contact and feces and the IRON LUNG. Polio destroys nerve cells and causes paralysis. It may well be the next viral disease eliminated by a vaccine.

Hanta Virus

Hanta virus ____________________________________ _________________________. The result is _________

_________________________________________________________________________________. There is no vaccine so avoid contact with mice!

West Nile Virus

West Nile virus is transmitted __________________________ _________________________________________. The virus ______________________________________ (encephalitis). There is no vaccine so avoid contact with mosquitoes.

____________________________________________________________________________________________________.

HIV (Human Immunodeficiency Virus)

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____________________________________________________________________________________________________. Transmission of the virus is ________________________ ___________________________. It is estimated that 50 million people are infected worldwide. There is no vaccine but there are effective drugs that can slow the disease but not cure it.

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Ebola

Ebola was first recognized in 1976. It is _________________

_________________________________________________________________________________________________. There is no vaccine but outbreaks have been controllable - although there is a major outbreak as this is being written (July 27, 2014) in West Africa with over 700 cases and 600 deaths confirmed. This virus is often the source of inspiration for movies such as "Outbreak".

Preventing Viral Diseases

Antibiotics are __________________________________________. Antibiotics are designed to disrupt the metabolism of organisms. They work on bacteria but _________ ___________________________________________________________________________________________________. The best way to stop viral infections is to prevent them from getting into the body to find a host cell.

The term ____________________________ is often used to describe the degree to which a particular pathogen is infectious.

The human body has 3 major l ines o f d e f e n s e against disease caused by viruses and bacteria:

1. The primary line of defense is made up _______________________________ ____________________________. These barriers include: skin, hair, earwax, boogers, saliva, stomach acid, cilia in the throat, mucus, tears, oil, etc.

The first line of defense is almost always enough to stop invaders. However, ________________________________________________________________and the pathogens are able to move inside the body.

When this happens ________________________________________________ ___________________________________________________________________________________________________________. These are the secondary and

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tertiary lines of defense.

2. The secondary line of defense is made up of Phagocytic white blood cells that deactivate and then engulf the viruses destroying them. When the secondary line of defense cannot destroy the invaders the tertiary line of defense is activated.

3. The tertiary line of defense is made up of _______________________. _____________________________________________________________________________________________. The antibodies find the chemical signal the antigen is excreting and latches on to it. Different pathogens have different markers. Antibodies are made specific to each marker. B-Cells (_____________ _____________________________________________) release antibodies that tag the incoming virus for destruction. _____________________________ ______________________________________________________________________________________________________. Viruses are destroyed later by phagocytic white blood cells.

Additional defense against viruses

_______________________ are produced by virus ____________________________. _______________________________________________________________________________________________________________________________________________________________________________. Interferons slow (interfere with…hence interferon) viral infection and allow WBCs and antibodies to respond.

As well, __________________________ are chemicals that _____________________ _________________________________ (cell-eating WBCs) in the blood. Pathogens are engulfed and digested by the phagocytes.

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Achieving Immunity

___________________________________ are used to produce immunity against pathogens. It is the process of infecting a person with a _________________________ ______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________.

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4.2 PRACTICE: VIRAL DISEASES

1. Why are antibiotic useless against viruses? (2 marks)

2. Please list at least 3 ways we can prevent viral infections from spreading. (3 marks)

3. Please pick one of the following topics to write a 1 page paper (~ 250 words) about. Please use the internet to research the topic. DO NOT PLAGERIZE! Attach completed assignment to and submit with the learning guide. (20 marks)

a. Vaccinations and how they work

b. Viral Disease (choose one…be sure it is VIRAL) identify name of virus identify name of disease caused by virus identify general structure of virus (RNA, DNA, enveloped, helical) mode of transmission (i.e., airborne, body fluids…) effects/symptoms treatments who it affects, where and when (history of outbreaks)

c. Compare and contrast the replication cycle of a biological virus versus a computer virus.

~ END OF BIOLOGY 11 UNIT 4 LEARNING GUIDE ~

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UNIT 4 ANSWER KEY

4.1 PRACTICE: STRUCTURE OF VIRUSES

1-12. Answers are not provided for fill-in the blank questions.

13. Please label and describe the function of the following viral structures on the diagram below. Please be neat. (12 marks)

o capsid o nucleic acido head o tailo tail fibers o plug

Capsid = protein coat that protects the viral genetic material (DNA or RNA) and allows virus to attach to host cells.

Head = capsid + viral genetic material (nucleic acid)

Tail fibers = help virus to attach to host cell

Nucleic acid = DNA or RNA, is the viral genetic material that encodes for the viral proteins

Tail = sheath + plug + tail fibers

Plug = hollow tube that nucleic acid passes through to go from virus into host.

4.2 PRACTICE: VIRAL DISEASES

1. Why are antibiotic useless against viruses? (2 marks)

Antibiotic directly translates to "against life" and are used to kill living cells by targeting some component or function that is necessary to sustain life. As virus are not living, antibiotics cannot limit the spread of viruses.

2. Please list at least 3 ways we can prevent viral infections from spreading. (3 marks)

Wash our hands. Eat well and get plenty of sleep so that our immune systems are in prime working condition to fight off viral infections. Vaccinations.

3. Answers will vary depending on topic chosen.

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