How to Use This Presentation • To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show.” • To advance through the presentation, click the right-arrow key or the space bar • From the resources slide, click on any resource to see a presentation for that resource • From the Chapter menu screen click on any lesson to go directly to that lesson’s presentation • You may exit the slide show at any time by pressing the Esc key Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Resources Chapter Presentation Transparencies Visual Concepts Standardized Test Prep Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Viruses and Bacteria Table of Contents Section Viruses Section Bacteria Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Viruses Objectives • Describe why a virus is not considered a living organism • Summarize the discovery of the tobacco mosaic virus • Describe the basic structure of a virus • Summarize the steps of viral replication • Explain how HIV infects immune system cells Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Viruses Is a Virus Alive? • All living things are made of cells, are able to grow and reproduce, and are guided by information stored in their DNA • Viruses are segments of nucleic acids contained in a protein coat Viruses are not cells • Viruses are pathogens—agents that cause disease • Viruses not grow, not have homeostasis, and not metabolize Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Viruses Virus Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Viruses Pathogen Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Viruses Is a Virus Alive?, continued Discovery of Viruses • Near the end of the nineteenth century, scientists were trying to find the cause of tobacco mosaic disease, which stunts the growth of tobacco plants • In 1935, biologist Wendell Stanley of the Rockefeller Institute purified tobacco mosaic virus (TMV) and determined that the purified virus is a crystal • Stanley concluded that TMV is a chemical rather than an organism Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Viruses Viral Structure • The virus protein coat, or capsid, may contain either RNA or DNA, but not both • Many viruses have a membrane, or envelope, surrounding the capsid • The envelope helps the virus enter cells It consists of proteins, lipids, and glycoproteins, which are proteins with attached carbohydrate molecules that are derived from the host cell Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Viruses Parts of a Virus Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Bacteria Important Bacterial Diseases Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Bacteria Pathogenic Bacteria, continued Bacterial Toxins • The second way bacteria cause disease is by secreting chemical compounds into their environment These chemicals, called toxins, are poisonous to eukaryotic cells • When bacteria grow in food and produce toxins, the toxins can cause illness in humans who eat those contaminated foods • Most bacteria can be killed by boiling water or various chemicals Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Bacteria Pathogenic Bacteria, continued Biowarfare • Biowarfare is the deliberate exposure of people to biological toxins or pathogens such as bacteria or viruses • Biologists are working on new approaches to recognize the onset of an attack with a bioweapon, to treat infected people, and to slow the spread of any outbreak of disease Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Bacteria Antibiotics • In 1928, the British bacteriologist Alexander Fleming discovered the antibiotic penicillin • Today different antibiotics are used to interfere with different cellular processes • Because these processes not occur in viruses, antibiotics are not effective against them Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Bacteria Antibiotics, continued Antibiotic-Resistant Bacteria • Some bacteria have become resistant to antibiotics • Susceptible bacteria are eliminated from the population, and resistant bacteria survive and reproduce, thus passing on their resistance traits • Usually, if the full course of the antibiotic is administered, all the targeted bacteria are killed and there is no chance for a resistant strain to develop If antibiotic treatment ends prematurely, some of the more-resistant bacteria may survive and reproduce Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Bacteria Importance of Bacteria Food and Chemical Production • Many of the foods that we eat, such as pickles, cheese, sauerkraut, olives, vinegar, and sourdough bread, are processed by specific kinds of bacteria • Humans are able to use different bacteria to produce different kinds of chemicals for industrial uses • Genetic engineering companies use genetically engineered bacteria to produce their many products, such as drugs for medicine and complex chemicals for research Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Bacteria Bacteria and Food Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Section Bacteria Importance of Bacteria, continued Mining and Environmental Uses of Bacteria • Mining companies can use bacteria to concentrate desired elements from low-grade ore • Bacteria metabolize different organic chemicals and are therefore used to help clean up environmental disasters such as petroleum and chemical spills • Powders containing petroleum-metabolizing bacteria are used to help clean oil spills Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Standardized Test Prep Multiple Choice The diagram below illustrates viral replication in bacteria Use the diagram to answer questions 1–3 Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Standardized Test Prep Multiple Choice, continued Which type of cycle is represented in the diagram? A B C D aerobic anaerobic lysogenic lytic Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Standardized Test Prep Multiple Choice, continued Which type of cycle is represented in the diagram? A B C D aerobic anaerobic lysogenic lytic Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Standardized Test Prep Multiple Choice, continued What is the virus doing to the bacterium in step 1? F G H J injecting its capsid injecting its DNA withdrawing proteins withdrawing DNA Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Standardized Test Prep Multiple Choice, continued What is the virus doing to the bacterium in step 1? F G H J injecting its capsid injecting its DNA withdrawing proteins withdrawing DNA Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Standardized Test Prep Multiple Choice, continued What is happening in step 4? A Viruses are entering the bacterium through a hole in the cell membrane B Viruses are repairing the cell membrane using viral proteins C Newly formed viruses are being released from the bacterium D The bacterium is ejecting its own chromosome inside a capsid Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved Chapter 20 Standardized Test Prep Multiple Choice, continued What is happening in step 4? A Viruses are entering the bacterium through a hole in the cell membrane B Viruses are repairing the cell membrane using viral proteins C Newly formed viruses are being released from the bacterium D The bacterium is ejecting its own chromosome inside a capsid Chapter menu Resources Copyright © by Holt, Rinehart and Winston All rights reserved ... the growth of tobacco plants • In 1935, biologist Wendell Stanley of the Rockefeller Institute purified tobacco mosaic virus (TMV) and determined that the purified virus is a crystal • Stanley concluded... Section Viruses Is a Virus Alive?, continued Discovery of Viruses • Near the end of the nineteenth century, scientists were trying to find the cause of tobacco mosaic disease, which stunts the growth... Describe why a virus is not considered a living organism • Summarize the discovery of the tobacco mosaic virus • Describe the basic structure of a virus • Summarize the steps of viral replication