Chapter 11

What is a fiber composite? How do cellular fiber composites resemble reinforced concrete?

What characteristics do desmosomes bestow on tissues that use these adhesions to connect adjacent cells? a. They allow communication between adjacent cells. b. They form a watertight barrier between the cells. c. They use the extracellular matrix to indirectly connect adjacent cells. d. They provide strong connections to resist pulling forces.

What does it mean to say that a signal is transduced? a. The signaling molecule enters the cell directly and elicits a cellular response. b. The signal is generated by the production of proteins. c. The physical form of the signal changes between the outside of the cell and the inside. d. The signal is amplified.

How do the extracellular fibers in plants differ from those in animals? a. Plant fibers resist compression forces; animal fibers resist pulling forces. b. Animal fibers consist of proteins; plant fibers consist of polysaccharides. c. Plant extracellular fibers never move; animal fibers can slide past one another. d. Plant fibers run parallel to one another; animal fibers crisscross.

What is the significance of the observation that many signal transduction pathways create a network, where they intersect or overlap?

Steroid hormones, like most lipid-soluble signaling molecules, are processed directly. How does the absence of a signal transduction cascade in the processing of steroid hormones affect (a) signal amplification, (b) signal regulation, and (c) the cellular response that is possible?

What type of foreplay is required for sexual reproduction in yeast? Some unicellular eukaryotes, including the yeast Saccharomyces cerevisiae, can reproduce sexually (see Chapter 13 ). At the most basic level, sexual reproduction involves the fusion of two cells and the combining of genetic material from each cell into one nucleus. Yeast cells are not motile, so the opposite mating types, referred to as "a" cells and "alpha (\alpha)" cells, must alter their growth (indicated by red staining in the photograph above) in order to attach and fuse. How does a yeast cell arouse this cellular reponse in the opposite mating type ? Yeast cells secrete signaling molecules called pheromones that are specific for their mating type. Type \(\alpha\) cells produce the pheromone \(\alpha\) factor, which binds to a G-protein-coupled receptor on type a cells, and vice versa. Explain what happens to the G protein when one of these receptors binds to a pheromone.

What type of foreplay is required for sexual reproduction in yeast? Some unicellular eukaryotes, including the yeast Saccharomyces cerevisiae, can reproduce sexually (see Chapter 13 ). At the most basic level, sexual reproduction involves the fusion of two cells and the combining of genetic material from each cell into one nucleus. Yeast cells are not motile, so the opposite mating types, referred to as "a" cells and "alpha (\alpha)" cells, must alter their growth (indicated by red staining in the photograph above) in order to attach and fuse. How does a yeast cell arouse this cellular reponse in the opposite mating type ? Instead of involving the production of second messengers, the pheromone- activated response in yeast involves a peripheral membrane protein related to Ras. Based on what you've learned about signal processing in multicellular organisms, predict how the pheromone signal in yeast is further processed in the cell to trigger the cell response.

What type of foreplay is required for sexual reproduction in yeast? Some unicellular eukaryotes, including the yeast Saccharomyces cerevisiae, can reproduce sexually (see Chapter 13 ). At the most basic level, sexual reproduction involves the fusion of two cells and the combining of genetic material from each cell into one nucleus. Yeast cells are not motile, so the opposite mating types, referred to as "a" cells and "alpha (\alpha)" cells, must alter their growth (indicated by red staining in the photograph above) in order to attach and fuse. How does a yeast cell arouse this cellular reponse in the opposite mating type ? Some of the intracellular proteins involved in the pheromoneactivated response in yeast are organized by a scaffold protein called Ste5. When pheromone binding occurs, one of these proteins, called Fus3, is released from Ste5 and triggers the response. Explain how this organization affects the speed of the response and amplification of the signal.

What type of foreplay is required for sexual reproduction in yeast? Some unicellular eukaryotes, including the yeast Saccharomyces cerevisiae, can reproduce sexually (see Chapter 13 ). At the most basic level, sexual reproduction involves the fusion of two cells and the combining of genetic material from each cell into one nucleus. Yeast cells are not motile, so the opposite mating types, referred to as "a" cells and "alpha (\alpha)" cells, must alter their growth (indicated by red staining in the photograph above) in order to attach and fuse. How does a yeast cell arouse this cellular reponse in the opposite mating type ? The cellular response to pheromone signaling includes assembly of microfilaments that direct growth toward the signal source. Propose a hypothesis that explains how growth might be limited to the region where signal receptors are activated.

What type of foreplay is required for sexual reproduction in yeast? Some unicellular eukaryotes, including the yeast Saccharomyces cerevisiae, can reproduce sexually (see Chapter 13 ). At the most basic level, sexual reproduction involves the fusion of two cells and the combining of genetic material from each cell into one nucleus. Yeast cells are not motile, so the opposite mating types, referred to as "a" cells and "alpha (\alpha)" cells, must alter their growth (indicated by red staining in the photograph above) in order to attach and fuse. How does a yeast cell arouse this cellular reponse in the opposite mating type ? Sex is dangerous in yeast-when cells are exposed to the pheromone of the opposite mating type, \(10-15\) percent of them die. For two yeast cells to fuse, portions of their cell walls must be broken down. How could you test the hypothesis that cell-wall destruction is responsible for pheromone-induced cell death in yeast?