Multiple Choice
IRS-1 is an essential adaptor protein in the insulin signaling pathway. If IRS-1 was under expressed in muscle cells, what effect would you expect to see on glycogen synthesis?
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12. Biosignaling
Insulin Signaling on Glucose Metabolism
Multiple Choice
Which statement best describes the role of insulin and glucose-transport proteins in glucose metabolism?
A
Insulin stimulates the translocation of GLUT4 transporters to the cell membrane, increasing glucose uptake into muscle and adipose cells.
B
Insulin directly phosphorylates glucose, allowing it to enter the cell without transport proteins.
C
Insulin inhibits the activity of glucose-transport proteins, reducing glucose entry into cells.
D
Insulin promotes the degradation of glucose-transport proteins, decreasing cellular glucose uptake.
Verified step by step guidance1
Understand the role of insulin in glucose metabolism: Insulin is a hormone secreted by the pancreas in response to elevated blood glucose levels. Its primary function is to facilitate glucose uptake into cells, particularly in muscle and adipose tissues, to lower blood glucose levels.
Learn about glucose transport proteins: Glucose transport proteins (GLUTs) are responsible for transporting glucose across the cell membrane. GLUT4 is the specific transporter that is insulin-responsive and is found in muscle and adipose cells.
Examine the mechanism of GLUT4 translocation: Insulin binds to its receptor on the cell surface, triggering a signaling cascade that results in the translocation of GLUT4-containing vesicles to the cell membrane. This increases the number of GLUT4 transporters on the membrane, enhancing glucose uptake into the cell.
Evaluate the incorrect statements: Insulin does not directly phosphorylate glucose; this is done by enzymes like hexokinase or glucokinase after glucose enters the cell. Insulin does not inhibit glucose transport proteins or promote their degradation; instead, it facilitates their activity by increasing their presence on the cell membrane.
Conclude with the correct statement: The correct description is that insulin stimulates the translocation of GLUT4 transporters to the cell membrane, increasing glucose uptake into muscle and adipose cells.
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