VIRUSES: Alive or Not?

RECALL: The SIX Characteristics of Life • Made up of cells • Made up of similar chemicals • Uses energy • Grows and develops • Responds to the world around them • Reproduces

WHAT IS A VIRUS?

The common cold virus - Rhinovirus

• Virus: small, nonliving

particle that invades and then multiplies inside a living cell.

– Do not use energy

to grow or to respond to their surroundings

– Cannot make food,

take in food, or produce wastes

Virus Shapes and Sizes

• Vary in shape and size – Round – Rod-like – Robot-like – Brick shaped • Although they vary in

size, all viruses are extremely tiny. The largest virus is no more than 250 nm long.

•

What’s a nanometer?

Virus Structure

1. Protein Coat - each virus has unique proteins on its coat, the shape of the proteins determine which cells it will attack.

2. Genetic Material - Either DNA or RNA

Viruses Can Only Multiply When They are Inside a Living Cell

• Viruses act like

a parasite because they destroy the host cells they take over when they multiply.

Two Types of Viruses • Once a virus enters the cell it takes over the cell’s functions.

• Some viruses take over right away, others wait a while.

– Active virus – Hidden virus

Examples of each kind: Hidden – HIV, herpes Active – Rhinovirus, Influenza, Chicken pox

How Do Viruses Multiply?

STEP ONE: ABSORPTION The virus attaches itself to the cell membrane

How Do Viruses Multiply?

STEP TWO: ENTRY The virus injects its genetic material.

How Do Viruses Multiply?

STEP THREE: REPLICATION The cell starts to produce the virus’s proteins and genetic material.

How Do Viruses Multiply?

STEP FOUR: ASSEMBLY New viruses assemble.

How Do Viruses Multiply?

STEP FIVE: RELEASE The cell bursts open releasing new viruses.

Hidden Viruses Multiply Differently • The only difference is that the hidden virus’ genetic material becomes a part of the organism for a while until it becomes active.

• See the difference here .

• Cep-1021

REMEMBER THE STEPS • ABSORPTION • ENTRY • REPLICATION • ASSEMBLY • RELEASE

Viral Diseases

1. Can cause some short-term sickness (Ex. Common cold) 2. Can cause death (Ex. AIDS) 3. Spread through physical contact or inhaled droplets 4. NO medications to cure viruses.

- medicines can treat the

symptoms

-

Our immune system (white blood cells) is our first defense

Preventing Viruses

Vaccines: substance that stimulates the body to produce chemicals that destroy viruses or bacteria.

- may be dead or altered viruses - they activate the body’s natural defenses

How are Antibiotics and Vaccines Different?

ANTIBIOTICS A chemical used to kill or slow the growth of bacteria VACCINES Virus introduced into the body in order to put the body “on alert.” If the virus ever infects the body, the immune system recognizes it and destroys it.

Why get a Vaccine?

– How are vaccines beneficial? – Besides vaccines, what other methods should be used to help prevent disease?

– Why do people still get the flu even though they’ve gotten the flu shot?

– Why not just get a SUPER Flu shot that covers them all?

EXAMPLES OF VIRUSES • Polio • Small pox • Human Papillomavirus • AIDS • Influenza • Herpes

How Viruses Effect Humans • HPV • More than 100

different strands

• Transmitted by direct

contact

• Symptoms: Warts or

none

• Very extreme case: –

Tree man

Measles – A Case Study

• Symptoms: Measles symptoms usually show up in two stages.

– Stage 1: runny nose, cough, and a slight fever. As the infection progresses, the – person's eyes become red and sensitive to light, and the fever rises.

– Stage 2 (3-7 days later) The fever reaches 103 appear on the gums and inside of the cheeks.

been. (hidden virus) complications.

• Prevention: Get vaccinated! Not so easy for some. o F-105 o F, and a red blotchy rash appears. The rash usually starts on the face and then spreads to the chest, back, and arms and legs,.The rash lasts for 4 to 7 days. Small white spots might also • Measles is very contagious. An uninfected person can get measles simply by breathing the air in a room where an infected person has – The virus can live in the air for 2 hours after an infected person leaves a room. Infected persons are usually infectious to others even before symptoms appear. • Complications: Pneumonia occurs in up to 6 percent of reported measles cases and accounts for 60 percent of deaths from measles. Encephalitis (inflammation of the brain) can also occur. – Infants under age 2 years and adults over age 20 have a greater risk of