Virus Tiny non-living particles Greek for poison

Big Question: Are viruses alive? Characteristics of living things: Made of one or more cells Grow Reproduce Responds to the environment Obtains and uses energy Gets rid of wastes

Basic Characteristics Up to 100 times smaller than bacteria Function is to reproduce Must have host cell to reproduce Named after the disease they cause or tissue they infect

Structure Inner core of nucleic acid (DNA or RNA) Surrounded by a protein coat Protein coat gives viruses many different shapes FluHIVEbola

Common Diseases Caused by Viruses Cold sores/herpes Warts Mumps Smallpox Rabies Measles HIV Hepatitis Flue Common Cold

Methods of Reproduction Lytic Cycle and Lysogenic Cycle

1 st Method: Lytic Cycle Attaches and enters the host cell through cell membrane Replication of the virus Host DNA destroyed Virus DNA is replicated and proteins are made using the host cell Assembly- new virus parts are put together Lysis (cell death) and release of new virus particles Host cell explodes and lets out new viruses

Virus binding to host type one: human infection 1)Receptors from the virus ensure they bind to the right kind of host 2)The virus rolls along the surface until it stops, the fuses with the cell 3)The viral DNA or RNA enters the cell

Instead of joining the cell, the virus injects the DNA/RNA into the host cell Virus Infection Type 2: Bacteria

Viral Replication Virus DNA hijacks the hosts replication proteins Host cell begins to make new virus nucleic acids and protein The parts of virus self assemble and are shipped out of the cell, or build up and the cell bursts Why might a virus want to build up until a cell bursts, rather than simply export out of the cell as they are made?

Lysogenic Cycle Attachment and entry into the cell through the cell membrane Provirus formation Viral DNA becomes part of the host chromosome Cell Division Virus is inactive but is replicated each time the host cell divides Provirus leaves chromosome Virus enter lytic cycle Host cell slowly releases new viruses

RetroViruses: The First Sleeper Agents 1)Viral DNA incorporates into host genome 2)It hangs out while everything is okay 3)Bails and blows the whole cell up when things are no longer okay

Viral Structure: Bacteriophage Head- hold the “brains” (DNA/RNA and proteins) DNA/RNA- nuclear membrane to code for proteins Internal Proteins- Allows the virus to gain a foothold once inside the cell

Tail Sheath/Neck- Structural, help with assembly and often have other proteins attached (some viruses can go “dormant”) Tail fibres- for attachment to host End plate- Attachment to the host and penetration of host membrane

Flu Virus (Animal Virus) Capsid- protein coat Lipid Envelope- like a cell membrane, helps protect virus from immune system Hemaglutinin- attachment to host cells Neuraminidase- helps to get virus out of host cell after replication

Major Viral Shapes An array of viruses. (a) The helical virus of rabies. (b) The segmented helical virus of influenza. (c) A bacteriophage with an icosahedral head and helical tail. (d) An enveloped icosahedral herpes simplex virus. (e) The unenveloped polio virus. (f) The icosahedral human immunodeficiency virus with spikes on its envelope.

Do questions page 360 #1-3 Copy figures 17-5 and 17-6 on the page provided and label the different stages. Compare what the virus does in both stages at the bottom of the page. Do Problem Solving Lab (hand in when complete)

Viral Infections How we fight the good fight

Viral Specificity Viral Specificity- viruses have adapted to infect certain species E.g. Pigs, Birds, and Humans are infected by similar flu viruses. Dogs are not.

Reasons for Viral Specificity #1 Reason: proteins on the virus only bind to specific receptors E.g. Polio binds to nerve cells, mumps to salivary glands, hepatitis to liver cells… these proteins tend to be highly variable species to species

The tail fibers in bacteriophages, or the capsids for animal viruses, bind to specific proteins

Your Bodies Defense Up until now, we only discussed how the viruses used and abused us… well it is time we fight back!

Primary Line of Defense Skin- provides a barrier between us and them Mucous membranes- protect in a similar way to skin, except mucus is typically transported elsewhere Tears- one of the first antibacterial substances (but many viral infections get in through the eyes so stop touching your face!) Ear wax- produced by the body and traps the invaders and keeps them from getting in

Secondary Line of Defense Innate Immune Response Non-Specific (ie. Will attack anything that isn’t you) Phagocytic white blood cells engulf viruses Natural killer cells Kill infected cells Absence of self- ie. Viral proteins showing up on the outside of a cell

Tertiary Line of Defense Adaptive Immune Response 2 Types of White blood cells B-Cells- produces antibodies that stick to viruses, act like a large group of 5 year olds attacking a grown man T- Cell Helper- Run around telling cells what to do “You- Produce antibodies. You! Eat something. No not that! Bacteria/Viruses!” Killer- aka Cytotoxic T lymphocytes- from the previous picture, finds infected cells and puts them down (triggers apoptosis)

Adaptive immune Response (in a nutshell) Innate immune response eats something infectious and wears it around telling other cells “this is one bad mambajamba” If it runs into a B or T cell with a receptor that matches the viral/bacterial protein, that cell kicks it into high gear, replicating a ton, and starts kicking butt and taking names

The first cut is the deepest Lag period while B-Cells reproduce and make antigens (3-15 days)

The second time though… Memory B-cells floating around recognize that jerk from last time Antibody numbers are way higher Response is much faster (3-7 days)

How do you think vaccines work? Read pages – Summarize what a vaccine is and how it works Do questions page 971 # 1-4 and page 976 #1-3 Do Problem Solving Lab