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Lecture 22.docx

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University of Toronto Scarborough
Gerald Cupchik

Question 1 - 642 You have been actively studying various signals produced within baby chimps. One day, you observe a ligand bind to a G-protein coupled receptor. You find out that the ligand is responsible for a deadly signal which could potentially kill the chimp. Since you are a caring and compassionate scientist, you are thriving to save this baby chimp. What can you do to stop the signal from being produced? Increase GRK(G-protein receptor kinase) levels Increase GDI(Guanine nucleotide dissociation inhibitors) levels Decrease GAP(GTPase activating proteins) levels Increase GEF(Guanine nucleotide exchange factors) levels Both A and B A. Correct; by increasing GRK, arrestin will bind to the receptor thus keeping the G-protein inactivated Question 2 - 645 Below is a list of steps involved in the signal transduction pathway of glycogen metabolism. Order the steps that have been listed and select the fourth. G protein activates of adenylyl cyclase cAMP activates protein kinase A Hormonal signal and receptor activation Many cAMP molecules are produced amplifying the signal PKA (protein kinase A) phosphorylates glycogen synthase and phosphorylase kinase Question 3 - 614 Which of the following process(es) can cAMP affect? Fatty acid formation. Assembly and disassembly of microtubules. Glycogen formation. All of the above. None of the above. Question 4 - 638 Identify the correct order of steps for the signal transduction pathway of glucose metabolism: 1) cAMP activates protein kinase A, 2) Hormonal signal and receptor activation, 3) PKA phosphorylates many targets, including both phosphorylase and glycogen synthase, 4) Many cAMP molecules are produced, 5) G protein activation of adenylyl cylcase 2,5,4,1,3 2,4,5,1,3 Question 5 - 630 Which of the following statements with regards to G-proteins and glucose metabolism is/are TRUE? Glucose can be used for energy by glycogen glucagon, or stored by glycogen insulin cAMP molecules are not produced, since the hormones involved in glucose metabolism do not bind to membrane-bound receptors of target cells (i.e. taken into cell by endocytosis) Enzymes involved in glucose metabolism are governed by the presence of hormones Glucocorticoids and epinephrine induce the same response of a target cell prior to glucose metabolism Question 1 - 647 State which of the following statements on G-proteins and their signaling pathway is true. G-protein is a heterodimer whose three sub units act as anchors to the membrane since they are linked to the membrane bound lipids The receptor changes it structure once the ligand binds to its extracellular domain, which allows it to bind to the G-protein The G-protein has two sub units which posses GTPase activity cAMP is a primary messenger which creates an amplified signal cAMP is produced once the alpha subunit binds to Adenylyl Kinase Question 2 - 643 Which of the following about phosphatases is false? Allows for rapid regulation of protein activity. Phosphorylates target molecules. Dephosphorylates target molecules. It can alter the catalytic activity of its substrates. Both b and d Question 3 - 625 Choose the correct statement below relating to the g-proteins: G-proteins are mostly heterodimers. alpha and beta subunits are linked to membrane bound lipids alpha and gamma subunits are linked to membrane bound lipids g-proteins interact only with receptors GDP is bound to beta subunits as it interacts with the effector Question 4 - 646 What would be the result of the phosphorylation of glycogen synthase and phosphorylase kinase? Glycogen synthase becomes inactive, producing more glycogen. Phosphorylase kinase becomes active, triggering enzymes to breakdown glycogen. Glycogen synthase becomes active, producing more glycogen. Phosphorylase kinase becomes inactive, triggering enzymes to breakdown glycogen. Glycogen synthase becomes inactive, no glycogen produced. Phosphorylase kinase becomes active, triggering enzymes to breakdown glycogen. Glycogen synthase becomes active, no glycogen produced. Phosphorylase kinase becomes active, triggering enzymes to breakdown glyco
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