1. Ch. 19 Biology

2.  Bacteria are prokaryotes w ith cells much smaller and more simply organized than those of eukaryotes  Viruses a re smaller and simpler than bacteria Virus Bacterium Animal cell Animal cell nucleus 0.25 µm

3.  Tobacco mosaic disease stunts growth of tobacco plants and gives their leaves a mosaic coloration  In the late 1800s, researchers hypothesized that a particle smaller than bacteria caused the disease  In 1935, Wendell Stanley confirmed this hypothesis by crystallizing the infectious particle, now known as tobacco mosaic virus (TMV)

4.  Viruses are particles of nucleic acid, protein, and in some cases, lipids.  Viruses can replicate only by infecting living cells. Copyright Pearson Prentice Hall

5.  Viruses differ widely in terms of size and structure.  All viruses enter living cells and use the infected cell to produce more viruses. Copyright Pearson Prentice Hall

6. A typical virus is composed of a core of DNA or RNA surrounded by a protein coat. A capsid is the virus’s protein coat. Copyright Pearson Prentice Hall http://img.sparknotes.com/figures/2/285caff64361a769a0850014b87c228c/structure.gif

7.  DNA viruses Genome is DNA  RNA viruses Genome is RNA Smaller than DNA viruses Lack of proofreading—leads to  evolution rate

8.  Capsid proteins bind to receptors on the cell surface and “trick” the cell into allowing it inside.  Once inside, viral genes are expressed and the cell transcribes and translates them into viral capsid proteins.  The host cell may makes copies of the virus, and be destroyed. Copyright Pearson Prentice Hall http://www.flutrackers.com/forum/attachment.php?attachmentid=326&d=1148840493

9.  Most viruses are highly specific to the cells they infect.  Viruses that infect bacteria are called bacteriophages. Copyright Pearson Prentice Hall

10.  Viruses that infect bacteria  Set in motion a genetic takeover of bacteria, such as Escherichia coli

11.  Once the virus is inside the host cell, two different processes may occur. Some viruses replicate immediately, killing the host cell (lytic cycle). Others replicate, but do not kill the host cell immediately (lysogenic cycle). Copyright Pearson Prentice Hall

13.  Lytic Infection In a lytic infection, a virus enters a cell, makes copies of itself, and causes the cell to burst. Copyright Pearson Prentice Hall

14.  First, the bacteriophage injects DNA into a bacterium.  The bacteriophage DNA forms a circle.  Phage DNA takes control and has cell make more phage DNA and proteins Copyright Pearson Prentice Hall

15.  Phage DNA and proteins are assembled into new bacteriophages  The cell lyses (bursts) and releases bacteriophages Copyright Pearson Prentice Hall

16.  Lysogenic Infection Other viruses cause lysogenic infections in which a host cell makes copies of the virus indefinitely. In a lysogenic infection, a virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cell's DNA. Copyright Pearson Prentice Hall

17. A lysogenic infection begins the same way as a lytic infection. The bacteriophage injects DNA into a bacterium. The bacteriophage DNA forms a circle. The viral DNA embedded in the host's DNA is called a prophage. Copyright Pearson Prentice Hall

18. Bacterial cell can divide normally through binary fission (copying the phage DNA as well). Phage DNA can exit the bacterial chromosome and then enter the lytic cycle. Copyright Pearson Prentice Hall

19.  Retroviruses contain RNA as their genetic information.  When retroviruses infect cells, they make a DNA copy of their RNA.  This DNA is inserted into the DNA of the host cell. Copyright Pearson Prentice Hall

20.  A retrovirus’ genetic information is copied backward—from RNA to DNA.  The virus that causes AIDS is a retrovirus. Human Immunodeficiency Virus (HIV) Copyright Pearson Prentice Hall

21.  Viruses are NOT living things. Viruses are not made of cells. Viruses must infect a living cell in order to grow and replicate. They have no metabolism--use host’s respiration, nutrition, and all other functions of living things. Copyright Pearson Prentice Hall

22.  Viruses have many of the characteristics of living things.  After infecting living cells, viruses can replicate, regulate gene expression, and even evolve. Copyright Pearson Prentice Hall

23.  Because viruses are dependent on living things, it seems likely that viruses developed after living cells.  The first viruses may have evolved from genetic material of living cells.  Viruses have continued to evolve over billions of years. Copyright Pearson Prentice Hall

24. Viruses that contain RNA as their genetic information are known as a)prions. b)oncoviruses. c)retroviruses. d)bacteriophage. Copyright Pearson Prentice Hall

25. The first type of virus to be studied was the a)bacteriophage. b)tobacco mosaic virus. c)influenza virus. d)AIDS virus. Copyright Pearson Prentice Hall

26. Which of the following statements about viruses is true? a)Viruses appear similar to bacteria when studied with a light microscope. b)Viruses display the essential characteristics of living things. c)Viruses can reproduce independently if they contain DNA. d)Viruses cannot reproduce unless they infect a living cell. Copyright Pearson Prentice Hall

27. A virus integrates its DNA into the DNA of the host cell but remains inactive for a while in a)a lytic infection. b)a lysogenic infection. c)neither a lytic nor a lysogenic infection. d)retroviral infection. Copyright Pearson Prentice Hall

28. Retroviruses are considered unique because a)they have RNA in their capsid and not DNA. b)they have DNA in their capsid and not RNA. c)after infection of a host cell, their RNA makes DNA. d)after infection of a host cell, their DNA makes RNA. Copyright Pearson Prentice Hall

29. Ch. 19 Biology

30. Copyright Pearson Prentice Hall  Bacteria and viruses are everywhere in nature, but only a few cause disease.  Disease-causing agents are called pathogens.

31. Copyright Pearson Prentice Hall  Bacterial Disease in Humans  Growth of pathogenic bacteria disrupts the body’s equilibrium by interfering with its normal activities and producing disease.

32.  Bacteria produce disease in one of two general ways. Some bacteria damage the cells and tissues of the infected organism directly by breaking down the cells for food. Other bacteria release toxins (poisons) that travel throughout the body interfering with the normal activity of the host. Copyright Pearson Prentice Hall

34.  Many bacterial diseases can be prevented by vaccines.  A vaccine is a preparation of weakened or killed pathogens.  When injected into the body, a bacteria/virus may prompt the body’s immunity to the disease.  Immunity is the body's ability to destroy new pathogens.

35. If infection occurs, drugs can be used to destroy bacteria. These drugs include antibiotics, which are compounds that block the growth and reproduction of bacteria. A reason for increased human life expectancy is an increased understanding of how to prevent and cure bacterial infections. Copyright Pearson Prentice Hall http://raleighway.com/who/c9b_ecoli_kirby.jpg

36. Copyright Pearson Prentice Hall There are various methods used to control bacterial growth, including:  sterilization  disinfectants  food processing

37. Copyright Pearson Prentice Hall Sterilization by Heat  Sterilization destroys bacteria by subjecting them to great heat.  Most bacteria are killed by prolonged high temperatures.

38. Copyright Pearson Prentice Hall Disinfectants  Disinfectants are chemical solutions that kill pathogenic bacteria.  They are used to clean rooms where bacteria may flourish.

39. Copyright Pearson Prentice Hall Food Storage and Processing  Bacteria can cause food to spoil.  Refrigerated food stays fresh longer because the bacteria will take longer to multiply.  Boiling, frying, or steaming can sterilize certain foods.  Heat kills the bacteria

40. Copyright Pearson Prentice Hall  Viruses produce disease by disrupting the body's normal equilibrium.  Viruses can attack and destroy certain cells in the body, causing symptoms of the disease.  Other viruses cause infected cells to change patterns of growth and development.

41. Copyright Pearson Prentice Hall  Viral diseases cannot be treated with antibiotics.  Vaccines are often the best protection against most diseases.  Most vaccines work only if used before an infection begins.  Symptoms may be treated with over-the- counter medicines.

42. Copyright Pearson Prentice Hall

43.  Viral Disease in Plants and Animals  Viruses produce serious animal diseases including foot-and-mouth disease.  Many viruses infect plants.  These viruses pose a serious threat to many crops.

44.  Antibiotics don’t work—no metabolic reactions to interfere with  Vaccines—harmless derivatives of pathogenic microbes that stimulate the immune system to mount defenses against the actual pathogen Parts of viruses, modified or killed viruses are injected into the body Allows immune system to make antibodies against specific markers on the viral coat  HIV mutates too fast for immune system to keep up with

45.  Influenza, also known as the flu, is a contagious disease that is caused by the influenza virus. It attacks the respiratory tract in humans (nose, throat, and lungs). The flu is different from a cold. Influenza usually comes on suddenly and may include these symptoms: Fever Headache Tiredness (can be extreme) Dry cough Sore throat Nasal congestion Body aches

46.  Emerging viruses are those that appear suddenly or suddenly come to the attention of scientists  Severe acute respiratory syndrome (SARS) appeared in China  Outbreaks of “new” viral diseases in humans are usually caused by existing viruses that expand their host territory

47. Young ballet students in Hong Kong wear face masks to protect themselves from the virus causing SARS. The SARS-causing agent is a coronavirus like this one (colorized TEM), so named for the “corona” of glyco-protein spikes protruding form the envelope.

48. Copyright Pearson Prentice Hall

49. Biologists know that bacteria can cause human disease by a)entering cells and using the cell to make new bacteria. b)producing toxic substances that interfere with normal cell function. c)decomposing the remains of dead organisms. d)changing atmospheric nitrogen into nitrogen compounds.

50. Copyright Pearson Prentice Hall A process that destroys bacteria by subjecting them to great heat is known as a)refrigeration. b)sterilization. c)pickling. d)boiling.

51. Copyright Pearson Prentice Hall Which of the following diseases is transmitted by a mosquito bite? a)influenza b)measles c)West Nile virus d)chickenpox

52. Copyright Pearson Prentice Hall The best way to combat viral diseases is a)to use antibiotics. b)to treat individual symptoms. c)to use preventive vaccines. d)to let the disease “cure itself.”