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False T or F: Gram-negative bacteria have a thick layer of peptidoglycan that stains purple. False T or F: Bacteria lack nuclei and therefore also lack genetic material. False T or F: Bacterial cells have membrane-bound organelles and chromosomes. False T or F: Bacterial cells are usually much larger than eukaryotic cells False T or F: Bacteria are incapable of movement themselves; they can only get to new locations by growing toward them or by forming endospores and being carried in air or water. True T or F: Some bacteria cannot survive in the presence of oxygen. False T or F: When bacteria undergo nonreproductive genetic recombination, their bacterial chromosome is altered. True T or F: Certain antibiotics have become ineffective against certain strains of bacteria. These bacteria have developed a resistance, which may be passed on from one generation of bacteria to the next. False T or F: The photoautotrophic bacteria are the only bacteria that are indirectly beneficial to humans. False T or F: Although viruses do not consist of cells, biologists consider them to be living because they are capable of reproduction. True T or F: Some viruses have a membranous envelope surrounding the protein coat that helps them gain entry into host cells. True T or F: Wendell Stanley made the important discovery that viruses are not cellular. False T or F: The largest virus is smaller than the smallest bacterium. True T or F: Viruses consist of RNA or DNA surrounded by a coat of protein. False T or F: Prions are the smallest known particles that are able to replicate. True T or F: A virus can only reproduce by controlling a cell. False T or F: Once a virus enters either a lytic or a lysogenic cycle, it cannot change to the opposite type of cycle. True T or F: Prophages and proviruses can both enter lytic cycles and destroy host cells. True T or F: People can contract the influenza virus more than once because the virus tends to mutate rapidly, avoiding the actions of the immune system. False T or F: Most scientists believe that viruses appeared on Earth before living cells and that living cells evolved from a virus-like entity. False T or F: Smallpox is caused by bacteria. True T or F: Chickenpox and shingles are caused by the same virus. False T or F: The viruses that have been linked to human cancers are usually transmitted through the air. True T or F: Emerging viruses normally do not infect humans, but they can when humans disturb their habitat. bacteria The earliest known group of living organisms on Earth was _________________. prokaryotic Bacteria are the only organisms characterized as _______________________. Gram stain, type of cell walls, and methods of obtaining energy Bacteria can be classified according to their ____________, ___________, and ___________. purple When tested with a Gram stain, gram-positive bacteria are stained ______________. A It is important to distinguish between Gram-positive and Gram-negative bacteria in diagnosing a bacterial infection because...A. Gram negative bacteria do not respond to many antibiotics. B. Gram-positive bacteria never cause fatal diseases. C. Gram-positive bacteria destroy antibiotics, preventing them from working. D. Gram-positive bacteria respond to many antibiotics. Prokaryotes Bacteria lack a true nucleus and membrane-bound organelles; therefore, they are classified as ___________________. a single molecule of DNA The cytoplasm of bacteria contains ___________________. a cell wall made up of peptidoglycan One difference between human body cells and bacterial cells is that bacterial cells have ______________________. cell nuclei, chromosomes, membrane bound organelles Structures found in a eukaryotic cell but not in a bacterial cell are ___________, __________, and ___________________. D Which of the following might be found in the cytoplasm of a bacterial cell? A. Chloroplasts B. Golgi bodies C. Mitochondria D. None of the above cell membrane and cell wall Bacterial cells have both a ______________ and _________________. ribosomes Cell organelles that E. coli and other bacteria have in common with eukaryotes are _________________. B Bacterial endopores... A. occur where there is plenty of available food. B. allow certain species to survive harsh environmental conditions. C. are similar to human tumors. D. can cause growth abnormalities in plants. pili E. coli is an example of a bacterium that has short, thin, hairlike projections called _____________________. flagella Which of the following are used by at least some bacteria for movement? B Autotrophic eukaryotes and autotrophic prokaryotes differ in that autotrophic eukaroytes...A. are cyanobacteria. B. can only use photosynthesis to manufacture their food. C. lack membrane-bound organelles. D. cannot manufacture their own food. B photosynthetic bacteria: sunlight:: A. chemotrophic bacteria : dead organisms B. chemoautotrophic bacteria : inorganic molecules C. photosynthesis : nitrification D. heterotrophic bacteria : inorganic molecules absence of water Which of the following conditions would be unsuitable for any kind of bacteria to grow? conjugation Bacterial cells such as E. coli transfer pieces of genetic material in a process called _____________________. C During the process of conjugation a. a virus obtains DNA from a host bacterium. b. a bacterial cell takes in DNA from the external environment. c. one bacterium transfers DNA to another. d. two bacteria exchange DNA. harmful to living organisms A pathogen is an agent that is ___________________. yogurt Which of the following foods are a fermentation product of bacteria? D Antibiotics a. include penicillin, tetracycline, and streptomycin. b. may prevent bacteria from making new cell walls. c. are very effective treatments for bacterial diseases. d. All of the above cellular, proteins, energy We know viruses are not alive because they are not ____________, they cannot make _______________, and they cannot use ______________. they are active inside living cells The study of viruses is a part of biology because ________________________. contain RNA or DNA in a protein coat Biologists now know that viruses ____________________. protective outer coat The capsid of a virus is the _________________. lipids, proteins, glycoproteins A membranous envelope surrounding some viruses may be composed of _______________, _________________, and ___________________. D All viruses have a. cytoplasm. c. mitochondria. b. ribosomes. d. None of the above D viruses : nucleic acids:: a. water : ice c. simplicity : complexity b. brick : wood d. a jigsaw puzzle : individual pieces D Tobacco mosaic virus a. is able to be crystallized. c. is smaller than a bacterium. b. causes disease in tobacco plants. d. All of the above 250 nm The largest known virus is about ________ in diameter. retroviruses Viruses that use reverse transcriptase to cause their host cells to transcribe DNA from an RNA template are called __________. C Which of the following contains only a nucleic acid? a. prion c. viroid b. virus d. All of the above B Unlike viruses, prions a. are capable of reproducing outside of a host cell. b. are composed only of protein. c. can infect brain cells of mammals. d. can be treated with antibiotics. C A typical virus consists of a. a protein coat and a cytoplasm core. b. a carbohydrate coat and a nucleic acid core. c. a protein coat and a nucleic acid core. d. a polysaccharide coat and a nucleic acid core. B Viruses a. are cellular organisms. b. reproduce only in living cells. c. have nuclei and organelles. d. are surrounded by a polysaccharide coat. B Animal viruses often infect only specific host cells because a. they must have the same DNA as their host cell. b. the host cell has specific receptors for the glycoprotein on the virus. c. viruses have receptors for host cell glycoproteins. d. the enzymes of the virus can attach only to specific host cells. Lysogenic In which type of cell cycle(s) does viral DNA become integrated into the host cell's DNA? C A prophage differs from a provirus in that a. a prophage contains DNA, while a provirus contains RNA. b. a prophage is formed during a lysogenic cycle, while a provirus is formed during a lytic cycle. c. a prophage contains DNA found in the infecting virus particle, while a provirus contains DNA produced from viral RNA. d. a prophage becomes integrated into a host cell's DNA, while a provirus cannot become integrated into a host cell's DNA. C Antibiotics are ineffective against viral infections because a. viruses are protected inside their host cells. b. viruses have enzymes that inactivate the antibiotics. c. antibiotics interfere with metabolic processes that viruses do not perform. d. viral protein coats block the antibiotics from entering the virus. D Which of the following is not a viral disease of humans? a. hepatitis b. rabies c. shingles d. All of the above are viral diseases of humans. A Which of the following is not a virus linked to cancer? a. Ebola c. hepatitis B b. human papillomavirus d. Epstein-Barr clearcutting forests Which of the following human activities is most closely associated with emerging viruses? spirilli Spiral bacteria are called ____________________. cocci Spherical bacteria are called ____________________. bacilli Rod-shaped bacteria are called ____________________. gram-staining The procedure used to distinguish between two types of bacterial cell wall structures is called ____________________. endospores Protective structures that some bacteria may form under harsh conditions are ____________________. peptidoglycan The cell walls of Gram-negative eubacteria are composed of a combination of polysaccharide and polypeptide called ____________________. chemoautotrophic Bacteria that obtain their energy by removing electrons from inorganic molecules, rather than obtaining energy from the sun, are called ____________________ bacteria. photoautotrophs In general, organisms that obtain their energy from sunlight are called ____________________. saprophytes Bacteria that are heterotrophic and feed on dead organic matter are called ____________________. antibiotic A(n) ____________________ is a substance that can be obtained from bacteria or fungi and can be used as a drug to fight pathogenic bacteria. decomposers; photosynthetic Many bacteria are ____________________ and play an important role in recycling carbon, nitrogen, and other elements, while other bacteria are ____________________ and assemble organic compounds from carbon dioxide, nitrogen, and other elements. capsid The protein coat of a virus is called a(n) ____________________. icosahedron; helix Most viruses occur in the shape of a(n) ____________________ or a(n) ____________________. retrovirus A virus that transcribes DNA from an RNA template is called a(n) ____________________. reverse transcriptase An enzyme called ____________________ manufactures DNA that is complementary to a virus's RNA. bacteriophages ____________________ are bacterial viruses with a polyhedral head and a helical tail. cell All viruses reproduce by taking over the reproductive machinery of a ____________________. lysogenic Viruses that infect a host cell and have their nucleic acid replicated but do not harm the host cell are in a ____________________ cycle. provirus A viral DNA molecule formed from an RNA virus is called a(n) ____________________. HIV The virus that causes AIDS is called ____________________. cancer Some viruses are thought to induce ____________________, a disease characterized by uncontrolled cell division. Ebola An example of an emerging virus is the ____________________ virus.