8. Which of the following statements about molecular switches is true?
a. Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off.
b. Protein phosphatases transfer the terminal phosphate from GTP onto a protein.
c. Serine/Threonine kinases are the most common type of protein kinase.
d. A GTP-binding protein exchanges its bound GTP for GDP.
9. What happens when a cell-surface receptor activates a G protein?
a. The beta subunit exchanges bound GDP for GTP.
b. The GDP bound to the alpha-subunit is phosphorylated to form bound GTP.
c. The alpha subunit exchanges bound GTP for GDP.
d. None of the above.
10. You are interested in how cyclic-AMP-dependent protein kinase A (PKA) functions to affect memory. It is known that in the cells you are studying, PKA works via a GPCR pathway. Furthermore, activated PKA phosphorylates the transcriptional regulator called Nerd, which then activates transcription of the gene Brainy. Which situation described below will most likely lead to an increase in Brainy transcription?
a. A mutation in the Nerd gene that produces a protein that cannot be phosphorylated by PKA.
b. A mutation in the gene that encodes cAMP phosphodiesterase that makes the enzyme inactive.
c. A mutation in the gene that encodes adenylyl cyclase that renders the enzyme unable to interact with the alpha subunit of the G protein.
d. None of the above.