91 Visual Connection Questions

1. Figure 9.8 HER2 is a receptor tyrosine kinase. In 30 percent of human breast cancers, HER2 is permanently activated, resulting in unregulated cell division. Lapatinib, a drug used to treat breast cancer, inhibits HER2 receptor tyrosine kinase autophosphorylation (the process by which the receptor adds phosphates onto itself), thus reducing tumor growth by 50 percent. Besides autophosphorylation, which of the following steps would be inhibited by Lapatinib?

1. Signaling molecule binding, dimerization, and the downstream cellular response.
2. Dimerization, and the downstream cellular response.
3. The downstream cellular response.
4. Phosphatase activity, dimerization, and the downstream cellular response.

2. Figure 9.10 In certain cancers, the GTPase activity of the RAS G-protein is inhibited. This means that the RAS protein can no longer hydrolyze GTP into GDP. What effect would this have on downstream cellular events?

3. Figure 9.17 Which of the following statements about quorum sensing is false?

1. Autoinducer must bind to receptor to turn on transcription of genes responsible for the production of more autoinducer.
2. The receptor stays in the bacterial cell, but the autoinducer diffuses out.
3. Autoinducer can only act on a different cell: it cannot act on the cell in which it is made.
4. Autoinducer turns on genes that enable the bacteria to form a biofilm.

4. Figure 9.18 What advantage might biofilm production confer on the S. aureus inside the catheter?