Biology | Answers to Review Questions

Author Dr. George B. Johnson, Washington University
Author Dr. Peter H. Raven, Missouri Botanical Gardens & Washington University
Contributor Dr. Susan Singer, Carleton College
Contributor Dr. Jonathan Losos, Washington University

Answers to Review Questions

Chapter 34 (p. 692)

1. Most species of bacteria are identified by their metabolic actions, which are determined by how they respond when grown on different growth media.

2. Prokaryotes differ from eukaryotes by (1) multicellularity - bacteria are not multicellular; (2) cell size - bacteria are very small; (3) chromosomes - bacteria lack a nucleus and DNA is not complexed with proteins; (4) cell division and genetic recombination - bacteria do not have true sexual reproduction, but do have means to transfer genetic material; (5) internal compartmentalization – bacteria lack membrane-bound organelles; (6) flagella - bacterial flagella are composed of single fibers of flagellin; (7) autotrophic diversity - bacteria have several different kinds of aerobic and anaerobic photosynthesis with a variety of end products including sulfur, sulfates, and oxygen; other bacteria are chemosynthesizers, metabolizing various inorganic and organic compounds.

3. The bacterial cell wall is a network of polysaccharide molecules cross-linked by polypeptides. Gram-positive bacteria have a plain polypeptide-linked polysaccharide wall, whereas gram-negative bacteria have an additional layer of large lipopolysaccharide molecules deposited over a plain layer. Gram-negative bacteria are generally more resistant to most antibiotics because of the nature of the cell wall.

4. Archaebacteria differ from the Eubacteria in a number of ways, most notably in the rRNA base sequences, the absence of muramic acid in their cell walls, and their often extreme habitats (anaerobic, very salty, very hot, etc.). Their unique metabolism allows them to synthesize methane from carbon dioxide and hydrogen, generating energy along the way.

5. Mutation is important because with rapid generation time, populations can double within several minutes, allowing a favorable mutation to be represented in large numbers quickly.

6. Genes coding for the type III system are similar to the genes that code for bacteria flagella; their proteins may be involved in getting virulence proteins into a host cell. Once inside, the type III proteins of Yersinia are injected into macrophages where they disrupt the signals that instruct the macrophage to engulf bacteria. Salmonella and Shigella type III proteins enter the cytoplasm of the eukaryote’s cells and are protected from its immune system.

7. STDs are sexually transmitted diseases. Viral STDs include: AIDS, herpes simplex, and genital warts (HPV); bacterial STDs include gonorrhea, syphilis, and chlamydia. Chlamydia is an unusual bacterium because although it is susceptible to antibiotics, it requires host genetic machinery to replicate its DNA.