What is a Virus?

http://www.virology.net/Big_Virology/BVretro.html

Virus: (Not living)

• Particle of nucleic acid, protein, and in some cases, lipids

• Reproduce only by infecting living cells

• Vary in size and structure

Structure of Virus

• Core of RNA or DNA

• Surrounded by a Protein Coat (capsid)

Function of Viruses:• Invade specific kinds of

cells (host)• Once inside host, viral

genetic info. is expressed (takes cell hostage & instructs the cell to make viral copies until cell is destroyed- explodes)

Diseases Caused by Viruses• Autoimmune

Difficiency Syndrome (AIDS)

• Common Cold• Small Pox• Influenzae- aka

“flu”• Warts

http://web.uct.ac.za/depts/mmi/stannard/fluvirus.html

Viruses• Must infect a living cell in order

to reproduce

• “Parasites”

Characteristic Virus Living Cell

Structure DNA or RNA

Core and a protein coat/capsid

Cell membrane, cytoplasm, eukaryotic

Reproduction Only within a host cell

Independent Cell Division (asexual or sexual)

Genetic Code DNA or RNA DNA

Growth & Development

No Yes- increase in # & differentiation

Obtain & Use Energy

No Yes

Evolve Yes Yes

Response to Environment

No (individual cells) Yes

Viruses

• Prevention through Vaccines- given before an infection begins

• Treatment- only the symptoms of viruses can be treated

• Antibiotics do not work on Viruses!

What are Bacteria?

Bacteria

• Prokaroytic- NO nucleus

• Living Cells- cell walls, cell membrane, pilli, DNA, cytoplasm

Capsule

Cell Wall

Cell Membrane

Pilli

Cytoplasm

DNA

Importance of Bacteria:

• E. coli live in our intestines & produce vitamins for us

• Decomposers

• Fix nitrogen for plants

• Use to make foods/beverages

Importance of Bacteria: cont.

• Industry- oil eaters

• Remove waste products/poisons from water

• Make medicines & chemicals through genetic engineering

Disease Causing Bacteria

• Streptococcus- “strep throat”; releases toxins into blood which can cause scarlet fever (rash)

• Diptheria- infects tissues of throat releasing toxins into blood where they destroy tissues---breathing problems, heart failure, paralysis, death

Prevention and Treatment:

• Vaccines stimulate immune system to produce antibodies (soldiers)

• Antibiotics can block the growth & development of bacteria

Controlling Bacteria

• Sterilization by Heat

• Disinfectants

• Proper Food Storage and Processing- refrigeration/freezing and cooking/canning correctly

LET’S

PRACTICE NOW……………..

Bacteria that grow in the presence of the antibiotic, penicillin, develop holes in their cell walls. Which of the following explains why penicillin is effective against some bacteria?

A. Water enters the holes in these bacteria and causes osmotic rupture.

B. Penicillin causes the flagella to become inactive.

C. The pili of the bacteria puncture the penicillin.

D. Penicillin produces oxygen, which kills any kind of bacteria.

A is the correct answer• Penicillin causes osmotic rupture (holes in

the cell wall) in some bacteria. Osmotic rupture occurs when a cell wall is damaged and too much water enters the cell. This excess water causes the cell to rupture and die. Choice B is incorrect because flagella don’t play a role in causing infection. Choice C is incorrect because pili are structures that help bacteria to stick to surfaces and each other. Choice D is incorrect because oxygen doesn’t play a role in osmotic rupture.

Streptococcus infection in a person’s throat can cause pain and fever. Streptococcus can be controlled by antibiotics. Streptococcus is a —

• F virus

• G bacterium

• H protozoan

• J fungus

G is the correct answer as Streptococcus Is a bacterium controlled by antibiotics; F, H, & J are incorrect because they are not treated with antibiotics

Many species of bacteria can be found in the human mouth. Which of these explains the great variety of bacteria in the mouth?

• A Large volumes of air cause bacteria to change form.

• B Salivary glands cause mutations in bacterial populations.

• C The presence of nutrients makes the mouth a favorable habitat.

• D Calcium in the teeth provides a suitable pH environment

• C is the correct answer as bacteria need nutrients to survive and the mouth is a great place for warmth, moisture and food

Information About Sendai Virus:Some infants and children are infected with human parainfluenza virus type 1, also known as HPIV-1.• A vaccine against HPIV-1 is made of a low dose of Sendai virus.• Sendai virus has a similar structure to HPIV-1.• Sendai virus makes mice sick but does not make humans sick.

• Why is Sendai virus used as a vaccine against HPIV-1?

• F. It alters the protein coat of HPIV-1.• G. It makes cells chemically unrecognizable to

HPIV-1.• H. It forms a protective barrier against HPIV-1.• J. It triggers the production of antibodies that

fight HPIV-1.

J is the correct answer. Vaccines are made by using heat-killed viruses so that the body can recognize the foreign material and make antibodies (soldiers). These “soldiers” will recognize these foreign bodies if the body comes into contact with them again and prevent one from suffering from the disease.

People infected with the human immunodeficiency virus (HIV) have an increased risk of dying from secondary infections. Which of these best explains how HIV increases the danger of secondary infections?

• F. HIV produces antigens that damage

red blood cells.• G. HIV adds genetic material from

harmful microbes.• H. HIV destroys helper T cells.• J. HIV consumes beneficial microbes in

the body.

H is the correct answer. HIV destroys helper T cells which are part of one’s immune system. If these cells are destroyed, then the immune system cannot fight against secondary infections.

• Which of the following is found in both cells and viruses?

• A Silica

• B Genetic material

• C Digestive cavity

• D Flagella The correct answer is B. Genetic material, whether it be RNA or DNA, will be present in these organisms.

PUBLIC SERVICE ANNOUNCEMENT: Facts About the Flu Vaccine1. The vaccine may be administered either as a nasal spray or as an injection.2. Prior to administration, nasal-spray vaccines must be stored at 15°C or lower.3. In an experiment, vaccine recipients had 85% fewer flu episodes than nonrecipients.4. The vaccine virus is heat sensitive and fails to replicate at temperatures of 38°C–39°C.

• Which statement above makes the most valid argument in favor of receiving the flu vaccine?

• A. Statement 1

• B. Statement 2

• C. Statement 3

• D. Statement 4

The correct answer is C. Statement 3 makes the most valid argument in favor of receiving the vaccine. The other three statements just inform us of information that does not relate to the benefits of taking the vaccine. They are only telling us how to store it, take it and how it was made.