3 [3 pts total]. Consider the signaling cascade downstream of the epinephrine receptor, shown below. One of the results of epinephrine signaling is that glycogen is broken down to release glucose. What would be the effect on overall extent of glucose production via this pathway in the following two scenarios (assume the same strength and duration of signal in each case) – explain your reasoning in each case using no more than 280 characters per answer: Reception Binding of epinephrine to G protein-coupled receptor (1 molecule) Transduction Inactive G protein Active G protein (10^2 molecules) Inactive adenylyl cyclase Active adenylyl cyclase (10^2) ATP Cyclic AMP (10^4) Inactive protein kinase A Active protein kinase A (10^4) Inactive phosphorylase kinase Active phosphorylase kinase (10^5) Inactive glycogen phosphorylase Active glycogen phosphorylase (10^6) Response Glycogen Glucose 1-phosphate (10^8 molecules) Q3.1 1.5 Points A mutation that hyper-activated adenylyl cyclase [1.5 pts: 0.5 for effect, 1 for answer] Q3.2 1.5 Points A mutation that inactivated the phosphatase that dephosphorylates phosphorylase kinase [1.5 pts: 0.5 for effect, 1 for answer]
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1: A mutation that hyper-activates adenylyl cyclase would lead to an increase in the production of cyclic AMP (cAMP). This would result in a higher activation of protein kinase A (PKA), which in turn would increase the phosphorylation of glycogen phosphorylase Show more…
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Based on what you know about the G protein-coupled receptor signaling pathway, beginning from epinephrine binding to its receptor and following the signal cascade in the diagram below to activate glycogen phosphorylase a to break down glycogen, determine the impact of the following mutations on the signaling pathway: Epinephrine, Glucagon, Adenylyl cyclase, Cyclic Phosphodiesterase, 5'AMP, AMP, ATP, Protein kinase A, ADP, Phosphorylase, Phosphorylase kinase b, kinase a (inactive), kinase a (active), Glycogen, phosphorylase b (inactive), phosphorylase a (active), P, Protein phosphatase. Mutation causing inactivation of adenylyl cyclase: Choose... Mutation in the alpha subunit of the G protein such that it cannot hydrolyze GTP to GDP: More breakdown of sugar Less synthesis of glycogen Mutation in the alpha subunit of the G protein such that it cannot dissociate from the beta and gamma subunits: More synthesis of glycogen Less breakdown of glycogen More breakdown of glycogen to release sugar Less breakdown of sugar
Bryan V.
Cell communication relies on a cell producing and releasing a signal, the signaling molecule, and signal interpretation by the receiving cell. As an example, we will focus on the "fight-or-flight" response. Central to the "fight-or-flight" response, epinephrine secreted by the adrenal medulla induces cAMP increase and glycogen breakdown and glucose release from liver cells. Q1.1 Would there be a complete "fight-or-flight" response if the adrenal medulla cells do not release hormones? Q1.2 Would an injection of epinephrine trigger induction of glycogen breakdown and glucose release from liver cells in a person that is completely relaxed and not scared? Q1.3 Would liver cells with a mutant receptor that does not bind epinephrine release glucose during a "fight-or-flight" response?
Josee P.
QUESTION 8 The table below shows the velocity of the reaction catalyzed by the transpeptidase enzyme at various concentrations of substrate. Use the table to determine the Vmax and Km for this reaction. (Hint, it may help to draw a Michaelis-Menten or Lineweaver-Burk plot). QUESTION 9 Individuals with sickle cell anemia are often put on antibiotics to prevent infections. Upon treatment with an antibiotic, the Vmax of the transpeptidase reaction decreases slightly (ie: original Vmax is 10 units/time, inhibited Vmax is 6 units/time). What kind of inhibitor is the antibiotic? Irreversible Reversible and competitive Reversible and non-competitive QUESTION 10 The last question is short answer/essay. You should integrate what you have learned in class and put your ideas into words. When blood glucose levels are high, glucose is moved to the liver, where individual glucose monomers are linked together to form a storage molecule, called glycogen. This reaction is catalyzed by an enzyme called glycogen synthase. This reaction is both spontaneous and fast. Write ~1 paragraph discussing how you could change this reaction. Discuss how you could change the reaction so it is no longer spontaneous (note, focus on the reaction itself, not the transport into the liver). Then, discuss how you could keep the reaction spontaneous, but make it slower. (2 points)
Supreeta N.
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