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38 Cards in this Set

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What is the major function of insulin?
Store substrates for fuel.
What is the major function of glucagon?
Mobilize fuel substrates for the body to use.
Where is glucagon synthesized?
Pancreas (α-cells)
Where is insulin synthesized?
Pancreas (β-cells)
Where is somatostatin synthesized?
Pancreas (δ-cells)
Where is proinsulin converted to its active form?
Within the secretory granules of the pancreatic β-cells.
What glucose transporter is found on the surface of pancreatic β-cells?
GLUT2.
What is the "pancreatic glucose sensor" and why?
Glucokinase because of its high Km for glucose. As more glucose enters the pancreas, the more insulin is released.
What is the result of blocking K+ channels in β-cells?
Blocking K+ channels results in a greater release of insulin, induced by sulfonylurea drugs in Type II diabetics.
Sulfonylurea drugs will also increase intracellcular Ca which increases vesicle formation and release.
Describe the pattern of insulin secretion over time.
An injection of glucose reveals a sharp initial spike followed by a sharp drop of plasma insulin. A slower second phase ensues and plasma insulin begins to rise steadily.
What is the major function of insulin?
Store substrates for fuel.
What is the major function of glucagon?
Mobilize fuel substrates for the body to use.
Where is glucagon synthesized?
Pancreas (α-cells)
Where is insulin synthesized?
Pancreas (β-cells)
Where is somatostatin synthesized?
Pancreas (δ-cells)
Where is proinsulin converted to its active form?
Within the secretory granules of the pancreatic β-cells.
What glucose transporter is found on the surface of pancreatic β-cells?
GLUT2.
What is the "pancreatic glucose sensor" and why?
Glucokinase because of its high Km for glucose. As more glucose enters the pancreas, the more insulin is released.
What is the result of blocking K+ channels in β-cells?
Blocking K+ channels results in a greater release of insulin, induced by sulfonylurea drugs in Type II diabetics.
Describe the pattern of insulin secretion over time.
Biphasic. An injection of glucose reveals a sharp initial spike followed by a sharp drop of plasma insulin. A slower second phase ensues and plasma insulin begins to rise steadily.
In what situation would a patient have zero insulin in the circulation?
In Type I diabetes only. In every other situation, there is a basal release of insulin to the circulation.
What drugs works in opposition to sulfonylurea drugs?
Diazoxide.
What key event occurs following insulin binding to its membrane surface receptor?
The insulin-receptor complex is endocytosed, making the receptor unavailable for future binding.
What 2 events occur within seconds of insulin secretion?
1) Insulin binds to its receptor
2) The receptor activates its secondary messengers.
What events occur within minutes of insulin secretion?
1) Gene transcription
2) Increased ion transport
3) Ligand-mediated receptor internalization
4) Enzyme activity is modulated
What events occur within hours of insulin secretion?
1) Protein, lipid, and nucleic acid synthesis
2) Complete downregulation of the receptor
3) Cell growth
What are the anabolic effects of insulin on the liver?
1) Promotes glycogenesis (glycogen storage)
2) Promotes synthesis of TAGs, cholesterol, and VLDL
3) Promote protein synthesis
4) Promote glycolysis (use glucose in circulation)
*Excess glucose - use glucose in circulation and store the leftover.
What are the 3 anti-catabolic effects of insulin on the liver?
1) Inhibits glycogenolysis (do not mobilize glucose)
2) Inhibits ketogenesis
3) Inhibits gluconeogenesis
What effect does insulin have on glycogen synthesis?
Increases the synthesis of glycogen by increasing glucose uptake, promoting glycogen synthase, and inhibiting glycogen phosphorylase.
What effect does insulin have on protein synthesis?
Increases protein synthesis by increasing amino acid transport and stimulating ribosomes to synthesize proteins.
What effect does insulin have on lipids?
Promote triglyceride storage by activating lipoprotein lipase to release FFA's for storage as TAG, inhibits lipolysis.
Why is it especially dangerous for insulin levels to be low in plasma?
Because very high levels of insulin are required to uptake normal levels of glucose.
*What polypeptides are synthesized from transcription of the glucagon gene?
1) Glucagon
2) GLP-1 and GLP-2
What do GLP-1 and GLP-2 do?
They activate insulin secretion, opposing the action of glucagon.
What effect does stress have on plasma glucose levels?
Stimulate glucagon and inhibit insulin, so glucose will be released into the circulation.
What is the relationship between levels of glucose, insulin, and glucagon?
An injection of glucose results in increases of insulin, and a decrease in glucagon.
*How would the injection of a gluconeogenic amino acid (arginine) affect glucose, insulin, and glucagon levels?
Infusion of arginine would cause a very small increase of glucose, a sharp increase of insulin, and interestingly, a sharp increase in glucagon.
What substrates are produced when glucagon binds to receptors on the liver?
Glucose and ketone bodies.