QUESTION 11 What property of the voltage-gated potassium channels allows K ions to pass? O a. Two polypeptide subunits are synthesized when the membrane is depolarized, allowing K+ ions to pass. O b. Depolarization causes the subunits to temporarily disintegrate so that K* ions can pass through the membrane O c. The voltage-gated potassium channels open when the polypeptide subunits are disinhibited O d. Depolarization causes the four polypeptide subunits specific to the voltage-gated K channel to twist into a shape that allows K ions to pass QUESTION 12 Why does ACh slow the heart rate? O a. It stimulates muscarinic receptors that open potassium channels O b. It stimulates muscarinic receptors that close potassium channels O c. It stimulates nicotinic receptors that open potassium channels O d. It stimulates nicotinic receptors that close potassium channels 4

QUESTION 14 What switches off an activated G protein? A molecule of GDP replaces the GTP. There is an enzyme that reassembles the trimeric G protein. Ca2+ ions activate CAMKII, which inactivates the protein. The protein contains intrinsic GTPase activity which converts GTP to GDP. A phosphorylase enzyme removes the phosphate from the GTP.

Question 26

Question 7. What is the rate-limiting step in the formation of an actin microfilament?

QUESTION 14 Which of the following statements is FALSE?   A Microtubules will rapidly disassemble in response to a drop in the ATP concentration.   B G-actin monomers and alpha-tubulin/beta-tubulin dimers assemble into filaments in their ATP-bound and GTP-bound forms, respectively.   C Microtubules are stabilized by microtubule-binding proteins, such as Tau.   D Actin-binding proteins allow F-actin to assemble in cells in many different ways.   E Hydrolysis of ATP and GTP changes the conformation of the monomers once they are incorporated into actin filaments and microtubules, respectively.

QUESTION 4 Which of the following G protein subunits activate K+ channels in response to the GPCR for acetylcholine on heart muscle?   a. Galpha inhibitory.   b. G alpha stimulatory   c. G beta gamma dimer.   d. G alpha transducin.

Question 34 Which is the target cell response to ADH? O gluconeogenesis, saving glucose for the brain smooth muscle contraction in mammary ducts and milk let down O the insertion of aquaporin cells facilitates water reabsorption An increase in sodium channels and sodium ion reabsorption, water follows

QUESTION 42 Which of the following statements is INCORRECT? O a. In a protein kinase cascade, the signal is amplified at each step of the cascade. O b. The major difference between a cell that responds to a signal and one that does not is the presence of a receptor O c. Adenylyl cyclase is an enzyme that catalyzes the conversion of ATP to CAMP. Od. In a protein kinase cascade, variation in the response is not possible. O e. Signals can reach target cells in multicellular organisms by diffusion or by circulation in the blood.

Question 4. In an axon, where all of the microtubules are oriented with their minus end facing the cell body, a researcher observes vesicles transporting cargo toward the synaptic terminals. Which type of molecular motor protein do you predict is transporting these vesicles?

QUESTION 10 Which of the following is NOT true of intermediate filaments?   A They provide mechanical strength to cells.   B They are composed of 8 oppositely oriented tetramers that are assembled into a rope-like filament.   C They have a non-polar orientation.   D They are rigid and do not deform before breaking   E Keratins, neurofilaments, vimentin, and desmin are examples of intermediate filaments.