Chapter 13 Practice Quiz: Membrane Receptors & G-Protein Signals

Chapter 13 Practice Quiz  Due Nov 2 at 11:59pm  Points 10  Questions 10  Available until Nov 5 at 11:59pm  Time Limit 30 Minutes  Allowed Attempts 2 Take the Quiz Again Attempt History Attempt Time Score LATEST Attempt 1 9 minutes 10 out of 10 Correct answers are hidden.

Score for this attempt: 10 out of 10 Submitted Nov 2 at 1:46pm This attempt took 9 minutes. Question 1 1 / 1 pts Why are membrane receptor proteins often used to transfer information from the cell's environment to its interior? The molecular signal would over stimulate the signaling pathway if it were internalized. The signal molecule is too large and/or too polar to pass through the cell membrane. The signal molecule is transported into the cell by the receptor. The molecular signal is not soluble in the interior of the cell. Question 2 1 / 1 pts The GTPase activity of G proteins is important because the G proteins are active only when GDP is bound to them. the phosphate is used by downstream kinases to phosphorylate target enzymes. the phosphate released is an important secondary messenger. hydrolysis of the phosphoric anhydride bond provides energy for signal transduction.

it provides a method whereby the initial signal can be terminated. Question 3 1 / 1 pts After a period of time, Gα ceases to stimulate adenylyl cyclase. What is the consequence? The G-protein's GTPase activity removes a phosphate; Gα diffuses back to the βγ subunits. Adenylyl cyclase converts Gα GTP to cGMP; Gα diffuses back to the βγ subunits. Gα is phosphorylated to enable it to return to the βγ subunits. GDP binds to the G-protein. The βγ subunits bind to Gα, promoting its GTPase activity. Question 4 1 / 1 pts Which of the following steps would occur immediately after epinephrine binds to the β- adrenergic receptor Gαs diffuses to adenylyl cyclase. GTP displaces GDP in Gαs. The Gαs subunit must diffuse away from the βγ subunits. cAMP binds to Protein Kinase A.

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β-Arrestin binds to the receptor. Question 5 1 / 1 pts Which of the following describes how cAMP regulates protein kinase A? Cyclic AMP binds to the catalytic subunits, causing a conformational change that leads to increased activity. Cyclic AMP increases the transcription of genes for PKA. Cyclic AMP binds to the regulatory subunits of PKA, causing a conformational change that releases the catalytic subunits to carry out phosphorylation. Cyclic AMP phosphorylates PKA, causing a conformational change that leads to increased activity. Cyclic AMP binds to the regulatory subunits of PKA, promoting exchange of bound GDP for GTP that releases the catalytic subunits to carry out phosphorylation. Question 6 1 / 1 pts The hydrolysis of phosphatidyl inositol bisphosphate (PIP2) by phospholipase C generates what two secondary messengers? free fatty acids and a molecule in which inositol 4,5 diphosphate is linked via a phosphate to glycerol

diacylglycerol and inositol 4,5-bisphosphate diacylglycerol and inositol 1,4,5-triphosphate phosphatidyl inositol 3,4,5-triphosphate (PIP3) and cAMP diacylglycerol phosphate and inositol 4,5-diphosphate Question 7 1 / 1 pts The ability of calcium ions to regulate many biochemical processes is due to its ability to block Na+/K+ channels binding to calmodulin. the requirement of divalent cation cofactors in the hydrolysis of ATP. competition with other divalent cations such as the magnesium ion. the large concentration of calcium ions in the cell. Question 8 1 / 1 pts Why does calmodulin bound with calcium interact with target proteins but free calmodulin does not?

Calcium ion binding neutralizes negative charges on calmodulin such that electrostatic repulsion between it and negative charges on the target protein do not occur. Calcium ions serve to bridge negatively charged groups on calmodulin and the target protein. Calcium binding results in a conformational change in calmodulin, producing a structure that can be activated by protein kinase A–dependent phosphorylation. Calcium binding to regulatory subunits results in the release of the active catalytic subunits. Calcium binding results in a conformational change in calmodulin producing a structure that can bind to target proteins. Question 9 1 / 1 pts Although ligand binding to 7TM receptors initiates a signal transduction pathway by triggering a change in tertiary structure, another class of receptors involves dimerization upon ligand binding, and the intracellular protein kinase domains are brought together and activate one another by cross- phosphorylation. the intracellular domains acting as second messengers are proteolytically cleaved and free to move through the cytoplasm. the intracellular domains are brought together, undergoing a conformational change that activates the hydrolysis of PIP2 into diacylglycerol and IP3. the intracellular domains are changed from a conformation having little organized structure into a highly organized structure.

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the intracellular domains are brought together to promote a guanylate cyclase activity that produces cGMP as a secondary messenger. Question 10 1 / 1 pts Which of the following is a major effect of insulin binding to its receptor? dephosphorylation of substrates such as IRS-1 trimerization of the receptor autophosphorylation of tyrosine binding of phosphatidylinositol-3-kinase to the receptor Quiz Score: 10 out of 10 Previous Next https://quizlet.com/107751872/exam-4-chapter-13-flash-cards/ https://quizlet.com/130302523/biochemistry-chapter-14-signal-transduction-pathways-quiz-flash-cards/

Chapter 13 Practice Quiz

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