VIRUSES Chapter 18 VIRUS Latin word for poison

VIRUSES Chapter 18

VIRUS: Latin word for poison �Virus: Non-living, Non-living parasitic, biological particle. �All viruses cause some sort of disease. Some even cause cancer

VIRUSES do not “live” because: �They can not reproduce outside a “host” cell �They do not carry out cellular respiration �They do not grow or develop

Virus structure § DNA or RNA Core § Holds the genetic material that will affect the host § Capsid § Outer protein coat that enables the virus to enter certain cells.

Virus structure § Glycoproteins § Projections that help the virus attach to host § Not all viruses have glycoproteins.

Virus Size Viruses are smaller than the smallest cell

Virus Vocab �Host: a cell in which a virus �Host Specific: Specific most viruses replicates or bacteria will only affect a single host or a small group of host species • Examples: � West Nile Virus – affects birds, birds horses, and people � Influenza type B – affects only people peopl not others � Parvo – affects only dogs, dogs not other organisms

Types of Viruses

Bacteriophages

Phages � Viruses that attack bacteria are called bacteriophage or just phage � T-phages are a specific class of bacteriophages with icosahedral heads, double-stranded DNA, and tails

� The T-phages most commonly studied T-phages are T 4 and T 7 � They infect E. coli , an intestinal bacteria � Six small spikes at the base of a contractile tail are used to attach to the host cell � Inject viral DNA into cell

Viruses Blow Up the Cell the Affect!!! �Once the viral genes get inside a cell, the genes are expressed. �This genetic program causes the host cell to make copies of the virus. �In the process, the host cell is destroyed.

Viruses Blow Up the Cell they Affect!!! �There are two ways this can occur 1. The Lytic Cycle 2. The Lysogenic Cycle

The Lytic Cycle STEPS 1. Attach • Virus “docks” with host cell 2. Injection • Virus inject it’s DNA/RNA into host cell 3. Replicate • replication of virus parts 4. Lysis • cell ruptures and new virus’ invade tissues of the host Lysis – to break or rupture cells or cell membranes

The Lysogenic Cycle STEPS 1. Attach • Virus “docks” with host cell 2. Injection • Virus inject it’s DNA/RNA into host cell 3. Incorporate • DNA attaches to the cells own DNA 4. Time Goes By 5. Stress 6. Replicate • replication of virus parts 7. Lysis • cell ruptures and new virus’ invade tissues of the host

Examples of Lytic Viral Infections 1. Common Cold �How do we catch it? • Contact with contaminated objects; droplet inhalation �What are the symptoms? • Sneezing, Sore Throat, Fever, Headache, Muscle Aches

Examples of Lytic Viral Infections 2. Influenza �How do we catch it? • Contact with contaminated objects, droplet inhalation. �What are the symptoms? • Body Aches, Fever, Sore Throat, Nasal Congestion, Headache, Dry Cough, Fatigue.

Examples of Lytic Viral Infections 3. Ebola � How do we catch it? • exposure to blood or bodily secretions of an infected person, or through direct contact with the person. � What are the symptoms? • Sore Throat, Fever, Dry hacking cough, Weakness, Severe Headache, Joint and muscle aches, Diarrhea, Dehydration, Stomach pain, vomiting, Internal and external bleeding.

Examples of Lysogenic Viral 1. Herpes Viruses Infections �Once a person is infected with a herpes virus they are infected for life. �Examples: • Chicken Pox can reappear later in life as Shingles • HSV-1 (oral herpes) and HSV-2 ( genital herpes)

Example of a Retrovirus 2. HIV �How do we catch it? • Contact with contaminated blood or bodily fluids �What are the symptoms? • T cells (needed for normal immune function) are destroyed

� Retroviruses are viruses that contain RNA as their genetic information � Retroviruses get their name from the fact that their genetic information is copied backward, backward from RNA to DNA � HIV is the most infamous retrovirus

How Do Our Bodies Fight Viral Infections? ANTIBIOTICS DO NOTHING FOR VIRAL INFECTIONS!!! �After enough cell debris (from blown up cells) is detected your Immune system gets involved � Macrophages are large white blood cells that get rid of debris by eating it. � When they eat too much, they die. These dead cells and the cell debris are “puss”

How Do Our Bodies Fight Viral Infections? � Other white blood cells pick up viral particles from the battle and carry it to Lymph nodes � In the lymph nodes, they look for cells to fight this type of virus. � T- cells (thyroid cells) are called upon and go to the site of the infection to kill specific infected cells � B-cells (bursal cells) make antibodies that go to the site and kill free viruses

How Do Our Bodies Fight Viral Infections? �The best way to protect against most viral diseases lies in prevention, prevention often by the use of vaccines �Most vaccines provide protection only if they are used before an infection begins.