1. Viruses, bacteria, viroids, and prions can all cause infection.
Any disease-causing agent is called a pathogen.
1 nanometer (nm) = one billionth of a meter
100 nm
eukaryotics cells 10, ,000 nm
viruses nm
viroids nm
Most people stay healthy because our bodies defenses are able to prevent the growth of these pathogens, but when we become sick, that means that the balance has shifted in favor of the pathogens.
Prokaroytic cells are cells that do not have organelles, or organized structures inside of them; the DNA is not contained to one area.
prokaryotic cells ,000 nm
prion 2-10 nm

2. A prion is made only of proteins.
causes misfolding of other proteins
results in diseases of the brain
Prions fold incorrectly, and trigger other similar proteins to fold incorrectly as well. These misfolded proteins will build up, and eventually lead to lesions in the brain, and result in diseases of the brain. These have NO NUCLEIC ACIDS, because they are made of only proteins, so they are not considered to be “alive”.
Viroids are the smallest infectious pathogens, and are generally circular, single stranded RNA. (They barely meet the criteria for life) They do not code for proteins, but in fact, pair up with the RNA of the plant they are infecting, messing up the translation of the RNA, or messing up the proteins that should be made from that organisms RNA. These do not have a protein coat surrounding them.
A viroid is made only of single-stranded RNA.
causes disease in plants
passed through seeds or pollen

3. Viruses differ in shape, genetic material, and in ways of entering host cells.
non-living pathogen
can infect many organisms
Viruses have a simple structure.
genetic material (either DNA or RNA)
capsid, a protein shell
maybe a lipid envelope, a protective outer coat
Viruses straddle our definition of life. They contain RNA, or genetic information, which is surrounded by a protein coat, but they are not able to reproduce on their own, they must infect a suitable host cell in order to reproduce.
Vaccines can prevent the spread of a virus, and antiviral medications can slow the reproduction of the virus, but there is no known way to stop it completely.

4. Viral Shapes: depends on proteins of capsid
enveloped (influenza)
helical (rabies)
polyhedral (foot-and-mouth
disease)
capsid
surface proteins
nucleic acid
capsid
nucleic acid
lipid envelope
surface proteins
capsid
nucleic acid
lipid envelope
Surface proteins
Different viruses will take on different structures depending on the proteins they are made out of. Capsid = protein shell
Enveloped viruses consist of nucleic acid surrounded by either a helical or polyhedral core and covered by an envelope.
Polyhedral viruses consist of nucleic acid surrounded by a polyhedral (many-sided) shell or capsid, usually in the form of an icosahedron (20 faces).
Helical viruses consist of nucleic acid surrounded by a hollow protein cylinder or capsid and possessing a helical structure.

5. Bacteriophage: A type of virus that prey exclusively on bacteria
Bacteriophage: A type of virus that prey exclusively on bacteria. Viral DNA is injected into bacteria cell.
Also called a bacterial virus.
They will pretty typically have this shape. The DNA will be ejected down through the sheath, and into the bacteria cell after it latches onto the outside of the bacteria cell.
Phage = thing that devours

6. A bacteriophage is a virus that infects a bacterium.
capsid
DNA
tail sheath
tail fiber
HEAD
collar
T4 is a virus that infects E.Coli!
TAIL
Base plate

7. Plant Phages: Prey exclusively on seed plants
Causes mosaic patterns or discoloration on the leaves of tobacco plants
Tobacco Mosaic Virus

8. Animal Phages: Prey exclusively on animals.
Phage = a thing that devours
This virus moves to the respiratory tract of an individual, binds to the cell membranes of cells in your respiratory tract, and releases it’s DNA or RNA into your cells, where it can now reproduce it’s own genetic information, and takes over the functions of the cell. The copies of the virus move out of the cell, and eventually the cell dies, releasing the rest of the virus DNA.
The flu is an “enveloped” virus, and contains RNA, not DNA.
The Influenza Virus

9. Viruses enter cells in various ways.
bacteriophages pierce host cells
viruses of eukaryotes enter by endocytosis or fuse with the membrane

10. LYTIC CYCLE
This is one way in which viruses reproduce. The two cycles were discovered during early research on bacteriophages.
This cycle shows the virus phage attaching to the host cell and injecting it’s DNA into that bacteria.
That Viral DNA will then be replicated(copied) and it’s proteins will be made by the host cell’s enzymes and synthesis machinery.
The viral proteins and nucleic acids then assemble inside the host cell, and make many copies of itself.
The host cell then bursts open, releasing the newly replicated and assembled viruses, which will start the process all over again.

11. The Lysogenic cycle is a little bit different.
The virus still injects the host cell with DNA, but in the lysogenic cycle, the virus DNA integrates itself into the DNA of the bacteria, and becomes what is called prophage. The bacteria then reproduces, copying the prophage, and transmitting that viral DNA onto it’s subsequent cells.
Prophage = bacteriophage’s genetic information inserted into the circular DNA of a bacteria

12. These two different cycles are often showed together, because they start out the same way, and factors induce whether the lytic cycle of the lysogenic cycle will start.
If a cell is in stress or is low in nutrients, typically the lytic cycle will start. It all depends on the proteins present. Different proteins will induce different pathways.

13. Bacteriophage - lytic cycle
Attachment

14. Assembly & Lysis (release)
Are released viruses genetically the same as the original virus?

15. Lysogenic ticking time bomb 2 possible results
after cell divisions, lytic cycle kicks in or
viruses escape via budding, using host’s cell membrane; leaving host intact, but weakened.
The lysogenic cycle is considered a ticking time bomb because the virus lays format, and can for years, before going into the lytic cycle, where thousands of cells will start to lyse open, and cause a lot of damage. HIV is an example of this!
Chicken pox is a virus that starts off as lytic, then becomes lysogenic. When older people have a shingles outbreak, it’s the chicken pox virus in the lytic cycle once again.

16. 16

17. New vocab words for the cut-out activity:
Host- the cell the virus is infecting
Lysogenic bacteria- a bacterium that has a piece of the viral DNA embedded in its own DNA (has a prophage)
Prophage (provirus)- segment of viral DNA that is integrated in the host’s DNA
Cell Multiplication- host cell is dividing and dividing, all the while making copies of the viral nucleic acid
New vocab words for the cut-out activity:

18. Differences between Lytic and Lysogenic Cycles:
Lytic Cycle Lysogenic Cycle

19. Viruses cause many infectious diseases
There are many examples of viral infections.
- common cold

20. Viruses cause many infectious diseases
There are many examples of viral infections.
common cold
influenza

21. Viruses cause many infectious diseases
There are many examples of viral infections.
common cold
influenza
SARS
SARS = Severe Acute Respiratory Syndrome

22. Viruses cause many infectious diseases
HIV-infected white blood cell
There are many examples of viral infections.
common cold
influenza
SARS
HIV
The body has natural defenses against viruses.

23. RNA or DNA Viruses with RNA Viruses with DNA
Human immunodeficiency virus (HIV)
Influenza Viruses
Rabies
Viruses with DNA
Warts
Chickenpox
mononucleosis
RNA or DNA
The rabies virus infects the central nervous system, ultimately causing disease in the brain and death. The early symptoms of rabies in people are similar to that of many other illnesses, including fever, headache, and general weakness or discomfort. As the disease progresses, more specific symptoms appear and may include insomnia, anxiety, confusion, slight or partial paralysis, excitation, hallucinations, agitation, hypersalivation (increase in saliva), difficulty swallowing, and hydrophobia (fear of water). Death usually occurs within days of the onset of these symptoms.
Mononucleosis (mono) is caused by the Epstein-Barr virus.
Chickenpox is caused by the varicella-zoster virus. There is now a varicella vaccine for this.
RNA viruses mutate more often, so those viruses are the ones that are harder to treat, because they are constantly mutating and changing.
Viruses with DNA, those vaccines mutate much less frequently, that’s why those vaccines generally last for life.

24. How Viruses Change
Viruses can mutate when they copy the genetic material
Copy something wrong
Mistake may prove useful
More “fit” virus (more infections)

25. Some viral diseases can be prevented with vaccines.

26. Vaccines are made from weakened pathogens.
A vaccine stimulates the body’s own immune response.
Vaccines prepare the immune system for a future attack.
There are vaccines for both viral and bacterial pathogens. Viruses are weakened when in a vaccine, and bacteria are dead when in a vaccine.
When you get a vaccine, you are getting a weakened or dead form of it. This is because our bodies have natural defense systems. Our blood contains red blood cells that carry oxygen, and white blood cells for fighting infection. Our white blood cells consist mostly of macrophages, antibodies, B-lymphocytes and T-lymphocytes. Macrophages swallow up and digest germs but leave behind a part of the germ called antigens. Antibodies are produced by B-lymphocytes, and attack the antigens left behind by the macrophages. The T-lymphocytes are another defensive white blood cell and they attack cells that have already been infected. When we get a vaccine, our bodies are able to more easily kill off the invader. They make and use the tools they need to kill it off, and will remember what they needed to do to kill it off. If our bodies see the same invader again, they have the memory of what it took last time to kill it off, so the B-lymphocytes can much more readily create antibodies to kill the virus or bacteria off.
Some vaccines require more than one dose, because if you are given a dead form of the virus, your body may not build up a complete immunity, so more than one dose is necessary. Live vaccines are typically the most effective, and require only one dose. A booster shot is needed when immunity starts to wear off for certain viruses (like tetanus  painful muscle spasm from a bacteria).
Vaccines are the only way to control the spread of viral disease.

27. Immunity - achieved through presence of antibodies
Proteins produced by the body to neutralize or destroy toxins OR disease carrying agents
Disease specific!!!
Antigen
Any foreign substance in the body that triggers production of antibodies
Allergen, bacteria, virus, etc.

28. Types of Immunity Active Immunity Long lasting, sometimes lifetime
Usually takes several weeks to develop
Exposure to disease organism triggers antibodies to be made
Natural immunity: infection with the disease
Vaccine-induced: exposure to the weakened or killed form
Passive Immunity
Only lasts a few weeks or month
Protection is immediate
Person is given antibodies rather than producing them on their own
Newborn baby: from mother to placenta or through breastmilk
Blood products: receiving blood with antibodies

29. How are viruses transmitted?
Depends on the type of virus, but these are common ways:
Airborne/aerosol
Contaminated food/water
Vectors (infected animal bite)
Sexual contact
Contaminated blood products/transfusions
Other bodily fluids
Breast milk
Exposure at birth