Viruses & DiseaseChapter 19

Herpes virus

Virus- Latin for poison

1. A virus is a non-living particle made up of

a. genetic material (DNA or RNA; NOT both)

b. protein coat (capsid)

2. Can invade living cells.

3. Reproduce inside living cells.

4. Viruses ARE NOT CELLS!

Slide # 2

Protein coat

Nucleic acid

Tail

Tail Fibers

A virus depends upon a living cell for its existence, harming that organism in the process. Parasites

Relative Sizes of VirusesSlide # 3

The Structure Of a Virus

1. Viruses are made of a core of DNA or RNA surrounded by a protein coat (capsid)

2. The Nucleic core is either made up of DNA or RNA but NOT both.

Slide # 4

Bacteriophage: a virus that infects a bacterium.

TAKS Practice

One characteristic shared by a virus and a living cell is that both —

F store genetic information in nucleic acids

G have a crystalline structure

H gain energy directly from the sun

J use glucose for respiration

Correct answer: F

Autotrophs / producers

Cells do this

Cells don’t have this

Cells & viruses DO

Slide # 5

E. coli Infected with a Bacteriophage

What it looks like in real life. Bacteria are destroyed as viruses are released.

E. coli

Bacteriophage

Slide # 6

How Viruses Infect a Host Cell

A virus is specific in the type of cell it invades. Proteins on the virus capsid attach to specific binding sites (receptors) on the host cell. Small viruses enter host cell by endocytosis, shedding the capsid upon entry.

Other viruses inject the genetic information into the cell leaving the capsid structure behind; permanently attached to the outside of the cell.

Virus

Slide # 7

Viruses: Hijacking a Living Cell for Reproduction.

1. Virus attaches to cell.2. Virus injects genetic info into the host cell.3. Host cell DNA is destroyed. 4. Cell machinery is forced to make virus genome

and proteins.5. Viruses are assembled.6. Viruses break out of cell. *(Some viruses allow the cell to live as virus

factories. Viruses bud out without destroying the cell. -ex. HIV)

Slide # 8

Virus enzyme lyses thebacterium’s cell wall & releasesnew viral particles

Viral proteins & nucleic acids assemble into complete virus particles Virus takes over cell’s

metabolism, causes cell to make virus proteins and nucleic acids

Virus injects nucleic acid into cell

Virus attaches to cell wall

Bacteriophage

Bacteriophage DNA

Bacteriophage protein

Bacteriophage protein coat

Bacteriophage DNA

Bacterialchromosome

Lytic Cycle

Slide # 9 Viral Reproduction: The Lytic Cycle

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Viral proteins and nucleic acids assemble into complete viral particles

Viral enzyme lyses the bacterium’s cell wall, releases new viral particles

Viral DNA inserts itself into bacterial chromosome

Viral DNA (prophage) replicates with bacterium for many generations

Viral DNA (prophage) can exit the bacterial chromosome

Viral DNA forms plasmid

Bacteriophage DNA

Bacterialchromosome

Virus injects nucleic acid into cell

Prophage

Lytic Cycle

Lysogenic Cycle

A Lysogenic Infection

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Slide # 10

AIDSAcquired Immune Deficiency Syndrome

1. The immune crippling disease caused by the HIV virus in which the body becomes unable to protect itself against any secondary infections.

2. HIV-Human Immunodeficiency Virus

3. HIV infects the immune system cell called Helper T cells (-most important white blood cell involved in identifying infections.)

Slide # 11

Body Fluids with High Concentrations of HIV

1. Blood2. Semen/Vaginal fluids (as high as blood)3. Breast milk4. Pus from sores

Slide # 12

Low Concentrations of HIV

It is highly unlikely you will be infected if you come into contact with:

a.Sweat

b.Tears

c.Urine

d.Saliva (-highly possible if blood from mouth sores is present)

Slide # 13

How is HIV Spread?

1. ANY type of unprotected sexual activity (highest risk)

2. Sharing used drug needles

3. Pregnancy-from mother to child

4. Sharing razors- if blood is present

5. Kissing- if even the smallest amount of blood is present. (-membranes of mouth are thin enough for HIV to enter straight into the body.)

6. Tattoos /body piercing if equipment is not clean.

Slide # 14

How is HIV not spread

1. Shaking hands

2. Hugging

3. Swimming pools

4. Toilet seats

5. Insect bites

6. Donating blood

Slide # 15

Retrovirus

1. RNA virus that changes its RNA into DNA when inside the host cell.2. Contains reverse transcriptase enzymes.3. Example of a Retrovirus is HIV .

Slide # 16

Reproduction of HIV

Can HIV be cured?

1. NO! Drugs are available to manage the disease, but HIV stays in the body forever!

2. PROBLEM: RNA viruses mutate at a very high rate. A person with HIV under control can evolve resistance to the drug treatments.

3. Some infected persons have several strains of HIV in their bodies.

Initial infection- flu-like symptoms a few weeks after infection.Stage 1:HIV positive with no symptoms- can stay at this stage for up to 10 years, but still can pass on the virus.Stage 2:HIV positive with symptoms- person is said to have AIDS. Symptoms include:

– swollen glands, chronic diarrhea, loss of weight and appetite, fever, fatigue, skin rashes (lesions), night sweats, oral thrush. Life expectancy: 2 to 5 years.

What does HIV look like?

Death and AIDS

Stage III-Full blown AIDS-

a.Person dies of rare opportunistic infections that take advantage the weakened immune system:

b.Person dies in a matter of months.

c. AIDS related illnesses include rare cancers and Pneumonia.

Example

1. HIV Virus attaches to host cell’s surface

2. HIV seeks out the nucleus and injects its genetic information

3. HIV directs the cell to make new HIV virus parts, which are then assembled.

4. New HIV viruses break out of the cell, and spread to take over other host cells. The cell is destroyed (lysis) as a result.