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?

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.

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?

copyright cmassengale 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. copyright cmassengale

copyright cmassengale 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!! copyright cmassengale

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

copyright cmassengale 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 copyright cmassengale

copyright cmassengale 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 copyright cmassengale

copyright cmassengale 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 copyright cmassengale

copyright cmassengale Helical Symmetry -More of a rod shape. -Single protein subunit is repeated many times -Ex: Ebola, Influenza, Rabies copyright cmassengale

copyright cmassengale Icosahedral Symmetry More Spherical in shape A polyhedron having 20 faces each an equilateral triangle Ex: Adenovirus, poliovirus, and rhinovirus copyright cmassengale

copyright cmassengale 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 copyright cmassengale

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 .

Which is better? To Kill Not to Kill

Holly Gets Sick Pre-video Watch video and try to answer questions 1-12. 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?

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. copyright cmassengale

Virus Life Cycles

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)

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

How the flu virus attacks! https://www.youtube.com/watch?v=Rpj0emEGShQ

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 -----------> 2. Innate -------------> 3. Adaptive Tailored by pathogen Always present in the uninfected cell. Induced by infection

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.

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

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

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.

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?