Viruses

What is a Virus? Viruses are tiny, non-cellular, infectious agents that invade living cells and take over their machinery to make copies of themselves.

Cannot reproduce on their own Are not made of cells Viruses are NOT considered living based on the characteristics of life, because they: *Do not make/use energy or have any metabolism (they have no organelles) Cannot reproduce on their own Are not made of cells Do not grow/develop on their own

Are viruses living? no Why? Be specific? Does not have all the characteristics of life, cannot survive or reproduce without alone without a host, no metabolism, not made of cells

Virus Structure Bacteriophage 2. Tail 1.Capsid – made of protein, Infects bacterial cells 1.Capsid – made of protein, contains the genetic material (DNA or RNA) 2. Tail 3.Tail Fibres- used for attaching to target cell

HIV Influenza Antigens ‘The Flu’ Human Immunodeficiency Virus Influenza ‘The Flu’ 1.Capsid – made of protein, contains the genetic material (RNA) Antigens - made of lipids/glycoproteins, help the virus to attack and enter their target Also help the immune system to identify the virus

Flu Attack! How a Virus Invades Your Body <iframe width="560" height="315" src="https://www.youtube.com/embed/Rpj0emEGShQ" frameborder="0" allowfullscreen></iframe> <iframe width="560" height="315" src="https://www.youtube.com/embed/Rpj0emEGShQ" frameborder="0" allowfullscreen></iframe>

Viruses Vocab Viruses are obligate parasites – organisms that need to invade a living cell or being to survive and do not benefit them in any way Host - The organism/cell that a parasite exploits Viruses are pathogens – something that causes disease in the host cell/organism

What is a parasite? What is a host? What is a pathogen?

How Viruses Work Step One – Viruses attach to their specific target cell based on their antigens. This works like a lock and key, so viruses will only affect certain cells.

Step Two – virus injects its genetic information into the host

Step Three – Replication (copies)The cell now starts to make copies of the virus proteins and genetic information Step Four –Assembles-the different parts of the virus are assembled into full virus copies

Step Five – LYSIS (cell bursting apart) and the virus copies are released to infect other cells

What are the 5 steps of the Lytic Cycle? 1. attack 2. inject 3. replicate 4. assemble 5. Lysis

How Viruses Work

Lytic/Lysogenic Cycles Viruses can infect cells in two different ways Lytic Cycle (short cycle)If a virus enters and immediately causes infection with the 5 steps Ex. flu

Lytic/Lysogenic Cycles Viruses can infect cells in two different ways Lysogenic Cycle (long cycle) If a virus enters and remains dormant/inactive in the DNA before causing infection ex. HIV, Herpes

I’m a Virus! Rap Song

Immune Response-Your immune system recognizes viruses and bacteria based on their surface antigens Every cell in your body has your specific markers, so anything that looks different is marked by your body as an invader (this is why people need specific organ transplants and also why you can’t receive blood transfusions from everyone)

Immune Response The Immune System protects the body in two ways: 1. Nonspecific Response: Skin, mucus, sweat, tears, saliva, stomach acid,and inflammatory response (heat, redness, swelling, and white blood cells) 2.Specific Response: Body makes antibodies which seek out and kill specific antigens

Immune System, part 1: Crash Course A&P #45

Brace yourself for the next slide!! Immune Response The immune system is incredibly complex which is why it has an entire branch of science called immunology Brace yourself for the next slide!!

Specific Response There are many cells that are responsible for the specific immune response: Macrophages/Phagocytes- Large cells that ‘eat’ the virus/bacteria and show the T Cells and B Cells the antigen to target Helper T Cells – Cells that tell B Cells, Cytotoxic T Cells, and Natural Killer Cells what to do B Cells – Cells that make Plasma Cells and Memory B Cells Plasma Cells – Cells that make antibodies which target the virus/bacteria Memory B Cells- Cells that ‘remember’ the antigen so they can quickly kill the virus/bacteria if it shows up again later Cytotoxic T Cells – Cells that make poison granules to kill the virus/pathogen Natural Killer Cells - Cells that kill any infected or out of control (cancer) cells

Specific Response HIV attacks Helper T Cells which greatly weakens the immune system This is how HIV (the virus) causes AIDS - Acquired Immunodeficiency Syndrome (the disease)

Medication Antibiotics are medications that kill living cells so they are used against living pathogens like bacteria, (useless against viruses) Viruses are very difficult to target with medications because they are not living by our definition of life

Antibiotics treat strep throat, ear and sinus infections, pneumonia, any type of bacteria infection.

Vaccines help fight viruses. A vaccine actually contains weakened (dead, wrong use of the word) viruses that trigger the immune system to start making antibodies which will protect you in the future

Some Vaccines that are available Keep in mind that not all vaccines are 100% effective Currently available vaccines: *Hepatitis A, B Adenovirus HPV Anthrax Influenza (The Flu) Japanese Encephalitis Measles, Mumps, Rubella, Varicella Rabies Smallpox Meningococcal Typhoid Shingles Yellow Fever Varicella (Chickenpox)

Which of the following are viruses?

BACTERIA Virus

flu cold HIV H1N1 E. coli Herpes Staph infection Swine Flu Virus Rhinovirus flu Influenza virus HIV Herpes