1. A Outnumbering cellular life 10:1
DO NOW….
Draw a square on your paper.
Draw a triangle around the square.
Draw two different types of antennae extending from the triangle.
Draw several swiggly lines within the square.
Viruses
A Outnumbering cellular life 10:1
How does your drawing compare with Picture A on the next slide?

2. Picture A Influenza Virus Flu Virus Structure
Your drawing and picture A represent a virus. Align the
Parts you drew with the name of real virus parts from A.

3. What is a virus? What are some common features of a virus?
Did someone say virus?!
What is a virus? What are some common features of a virus?

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What are Viruses?
Virus:
- an infectious obligate intracellular parasite made up of genetic material surrounded by a protein coat and/or an envelope derived from a host cell membrane.
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Size of Viruses
Viruses are much smaller than a prokaryotic and eukaryotic cells
Fun Fact: Every time you sneeze you fire enough viruses to infect THOUSANDS!!
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6. Characteristics Contain a protein coat called the capsid
Have a nucleic acid core containing DNA or RNA
Capable of reproducing only when inside a HOST cell
- All viruses must make mRNA that can be translated by host ribosomes to make their proteins.
2 Life cycles (Lytic vs. Lysogenic)
Smaller than bacteria

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Characteristics
CAPSID
Some viruses are enclosed in an protective envelope
-Some viruses, the capsid is surrounded by this envelope which is a lipid bilayer derived form host cell membrane that contains viral proteins that can help virus bind to host cells.
Some viruses may have spikes to help attach to the host cell
Most viruses infect only SPECIFIC host cells
Must be metastable
- Must protect the genome (Stable) but must come apart quickly for infection (unstable)
DNA
ENVELOPE
SPIKES
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Capsid Structure
The capsids are made of individual protein subunits
Individual subunits are called capsomeres
Each subunit has “identical” bonding contacts with its neighbors. This leads to symmetric arrangement.
CAPSOMERES
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Viral Shapes
Viruses come in a variety of shapes
Some may be helical shape like the Ebola virus
Some may be polyhedral shapes like the influenza virus
Others have more complex shapes like bacteriophages
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Helical Symmetry
-More of a rod shape.
-Single protein subunit is repeated many times
-Ex: Ebola, Influenza, Rabies
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Icosahedral Symmetry
More Spherical in shape
A polyhedron having 20 faces each an equilateral triangle
Ex: Adenovirus, poliovirus, and rhinovirus
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Living or Nonliving?
What do you think?
Outside of host cells, viruses are inactive
Lack ribosomes to make enzymes needed for polypeptide synthesis & DNA replication.
Use the host cell’s organelles and enzymes to reproduce
EBOLA VIRUS
HIV VIRUS
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13. Used for Virus Classification
RNA or DNA Virus
Do or do NOT have an envelope
Symmetry of Capsid shape
HOST they infect
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14. Baltimore Classification System
Reverse Transcriptase - Enzyme that reverses the flow of genetic information - Used by retroviruses with (+) stranded RNA (HIV and Human T-Cell Leukemia Virus)

15. Write your answer in your notebook .
Select a Position
From the perspective of the virus, is it best for a virus to kill its host or to not kill its host?
Write your answer in your notebook .

16. Which is better?
To Kill
Not to Kill

17. Do Now
What does a cell need in order for a virus to successfully produce progeny?

18. Holly Gets Sick Pre-video
Watch video and try to answer questions Listen for specific types of human cells which help Holly to live or not.
Holly Gets Sick Pre-video
Successful Virus Infection:
Entry – just getting into body isn’t a guarantee
Spread – must get to the specific area in body
Multiply – infect specific cell type – go lytic!
Damage – cause illness
What will happen to Holly?

19. Bacteriophage (phage)
Virus which infects E.coli bacteria.
Phage uses tail fibers to attach to cell.
Only DNA is injected into cell.
Capsid remains outside cell.
Study picture to left. Notice only one
Phage completely without DNA (one
with white capsid.
Viral protein not needed inside cell
because it is the DNA that is the ]
information for making more virus.
Next slide shows the life cycle of a
Bacteriophage virus.
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20. Virus Life Cycles

21. 5 stages of the lytic cycle
Attachment and Entry
Translation
Genome Replication
Assembly
Release
- In order for a virus to successfully invade and replicate inside a cell, the host needs to be BOTH susceptible (has functional receptor to allow virus in) and Permissive ( can support viral replication)

22. Some viruses cause disease
Viral Diseases
Some viruses cause disease
Smallpox, measles, mononucleosis, influenza, colds, warts, AIDS, Ebola.
Some viruses may cause some cancers like leukemia
Virus-free cells are rare
MEASLES

23. How the flu virus attacks!

24. How Body Fights a viral infection or any pathogen
Host defenses:
- Physical and chemical
- Ex: Skin, Mucus, tears, low pH, surface cleansing…
Order of defenses:
1. Intrinsic > Innate > Adaptive
Tailored by pathogen
Always present in the uninfected cell.
Ex: Apoptosis, Anti-virial proteins, Autophagy
Induced by infection
Ex: Dendritic Cells, macrophages, Natural Killer Cells

25. How Body Fights a viral infection or any pathogen
Nonspecific: Doesn’t discriminate
Specific: Cells specifically id the virus
Fever
Macrophages
Nostril hairs, skin
Mucous
Natural Killer Cells
Interleukins
Antimicrobial proteins
Histamine and inflammation
Dendritic cell
Lymphocytes
T cells: Helper and Killer
B cells: makes antibodies
* Both specifically target the virus and mature in the lymph nodes
*Killer T and antibody destroy virus
Memory cell
Our immune system backs up our nonspecific defense system.

27. To the left is a macrophage using phagocytosis to
destroy bacteria. Below is a picture of tissue
damage showing macrophages destroying bacteria
at the site of tissue damage.
Illustration of tissue damage
Phagocytes (macrophages and neutrophils) consume bacteria and cell debris; tissue heals
Tissue injury; release of chemical signals such as histamine
Dilation and increased leakiness of local blood vessels; migration of phagocytes to the area

28. Not Required Information
B cells secrete antibodies that attack antigens ( anything foreign)
T cells attack cells infected with the
specific virus or pathogen.

29. Vaccines are our proven best defense against viruses
Vaccines mobilizes the host immune system to prevent virus infections (immune memory)
Vaccination breaks the chain of transmission
Vaccines can be Active or Passive
- Active = Giving a modified form of the pathogen or material derived from it that induces immunity to disease. Provided long term protection
- Passive= Giving the products of the immune response (antibodies or immune cells). Provides short term protection.
Fun Fact: You have a transferred maternal IgG natural passive vaccine from your mother.

30. Review questions
What is the difference between the lytic and lysogenic viral life cycles” What part of the virus remains outside the host cell? Goes into host cell? What part of the virus provides the genetic information to make more nucleic acid, capsids, envelopes and glycoprotein receptors? What part of the virus must be like the host cell? What is a vaccine? What are two ways in which you can achieve immunity from a infection? What is the difference between active immunity and passive immunity? Name all the types of immune cells and state their function. How can a viral or bacterial outbreak be prevented or controlled?