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Questions and Answers
Glucose-regulatory systems are activated by ______
Glucose-regulatory systems are activated by ______
hypoglycemia
The islets of Langerhans release ______
The islets of Langerhans release ______
glucagon
The hypothalamic glucoreceptors respond to abnormally low concentrations of ______
The hypothalamic glucoreceptors respond to abnormally low concentrations of ______
blood glucose
Epinephrine and adrenocorticotropic hormone (ACTH) can be released by the anterior pituitary in response to activation of the ______
Epinephrine and adrenocorticotropic hormone (ACTH) can be released by the anterior pituitary in response to activation of the ______
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ACTH increases ______ synthesis and secretion in the adrenal cortex
ACTH increases ______ synthesis and secretion in the adrenal cortex
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Liver glycogen is an essential postprandial source of ______
Liver glycogen is an essential postprandial source of ______
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Liver glycogen can meet the needs for only ______ hrs in the absence of dietary intake of CHO
Liver glycogen can meet the needs for only ______ hrs in the absence of dietary intake of CHO
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Glycogen is stored in the ______ for short-term maintenance of blood glucose homeostasis
Glycogen is stored in the ______ for short-term maintenance of blood glucose homeostasis
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Glycogen is stored in the ______ as a source of energy
Glycogen is stored in the ______ as a source of energy
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Gluconeogenesis is required to maintain blood glucose during ______ and ______
Gluconeogenesis is required to maintain blood glucose during ______ and ______
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Glucagon acts to maintain blood glucose levels by activation of hepatic ______ and gluconeogenesis.
Glucagon acts to maintain blood glucose levels by activation of hepatic ______ and gluconeogenesis.
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Glucagon is synthesized as a large precursor molecule (preproglucagon) that is converted to glucagon through a series of selective ______ cleavages, similar to those described for insulin biosynthesis.
Glucagon is synthesized as a large precursor molecule (preproglucagon) that is converted to glucagon through a series of selective ______ cleavages, similar to those described for insulin biosynthesis.
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The α cell is responsive to a variety of stimuli that signal actual or potential ______.
The α cell is responsive to a variety of stimuli that signal actual or potential ______.
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Amino acids derived from a meal containing protein stimulate the release of both glucagon and ______.
Amino acids derived from a meal containing protein stimulate the release of both glucagon and ______.
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Epinephrine and norepinephrine stimulate the release of ______.
Epinephrine and norepinephrine stimulate the release of ______.
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Glucagon is composed of 29 amino acids arranged in a single ______ chain.
Glucagon is composed of 29 amino acids arranged in a single ______ chain.
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Glucagon is considered one of the ______ hormones that oppose the actions of insulin.
Glucagon is considered one of the ______ hormones that oppose the actions of insulin.
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The α cell of the pancreas is responsive to a variety of stimuli including low blood glucose and amino acids derived from protein-containing meals, which stimulate the release of ______.
The α cell of the pancreas is responsive to a variety of stimuli including low blood glucose and amino acids derived from protein-containing meals, which stimulate the release of ______.
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Glucagon secretion is significantly decreased by: 1. Elevated blood glucose 2. ______. Both substances are increased following ingestion of glucose or a carbohydrate-rich meal.
Glucagon secretion is significantly decreased by: 1. Elevated blood glucose 2. ______. Both substances are increased following ingestion of glucose or a carbohydrate-rich meal.
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The intravenous administration of glucagon leads to an immediate rise in blood glucose. This results from an increase in the breakdown of liver (not muscle) glycogen and an increase in ______.
The intravenous administration of glucagon leads to an immediate rise in blood glucose. This results from an increase in the breakdown of liver (not muscle) glycogen and an increase in ______.
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Glucagon activates ______ in adipose tissue.
Glucagon activates ______ in adipose tissue.
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Glucagon increases uptake of amino acids by the liver, resulting in increased availability of ______ for gluconeogenesis.
Glucagon increases uptake of amino acids by the liver, resulting in increased availability of ______ for gluconeogenesis.
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Glucagon binds to high-affinity G protein-coupled receptors on the cell membrane of ______.
Glucagon binds to high-affinity G protein-coupled receptors on the cell membrane of ______.
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Glucagon binding results in activation of adenylyl cyclase in the plasma membrane, causing a rise in cAMP (the 'second messenger'), which, in turn, activates cAMP-dependent protein kinase and increases the ______ of specific enzymes or other proteins.
Glucagon binding results in activation of adenylyl cyclase in the plasma membrane, causing a rise in cAMP (the 'second messenger'), which, in turn, activates cAMP-dependent protein kinase and increases the ______ of specific enzymes or other proteins.
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Insulin and glucagon both play a role in maintaining ______.
Insulin and glucagon both play a role in maintaining ______.
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Between meals, blood glucose is derived primarily from ______ glycogen.
Between meals, blood glucose is derived primarily from ______ glycogen.
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Hypoglycemia may be divided into: 1. Insulin-induced Type I DM Hypoglycemia ______ is not affected by it 2. Postprandial Hypoglycemia exaggerated insulin release following a meal 3. Fasting hypoglycemia. Rare, pancreatic tumors 4. Hypoglycemia due to Alcohol intoxication in fasting individuals. NAD+/NADH ratio is decreased
Hypoglycemia may be divided into: 1. Insulin-induced Type I DM Hypoglycemia ______ is not affected by it 2. Postprandial Hypoglycemia exaggerated insulin release following a meal 3. Fasting hypoglycemia. Rare, pancreatic tumors 4. Hypoglycemia due to Alcohol intoxication in fasting individuals. NAD+/NADH ratio is decreased
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Inhibition of gluconeogenesis resulting from hepatic metabolism of ethanol can lead to ______ of insulin-induced hypoglycemia.
Inhibition of gluconeogenesis resulting from hepatic metabolism of ethanol can lead to ______ of insulin-induced hypoglycemia.
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Glucose-regulatory systems are activated by ______
Glucose-regulatory systems are activated by ______
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The hypothalamic glucoreceptors respond to abnormally low concentrations of ______
The hypothalamic glucoreceptors respond to abnormally low concentrations of ______
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Liver glycogen is an essential postprandial source of ______
Liver glycogen is an essential postprandial source of ______
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Glycogen is stored in the ______ for short-term maintenance of blood glucose homeostasis
Glycogen is stored in the ______ for short-term maintenance of blood glucose homeostasis
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Gluconeogenesis is required to maintain blood glucose during ______ and ______
Gluconeogenesis is required to maintain blood glucose during ______ and ______
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ACTH increases ______ synthesis and secretion in the adrenal cortex
ACTH increases ______ synthesis and secretion in the adrenal cortex
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Glucagon is synthesized as a large precursor molecule (preproglucagon) that is converted to glucagon through a series of selective ______ cleavages, similar to those described for insulin biosynthesis
Glucagon is synthesized as a large precursor molecule (preproglucagon) that is converted to glucagon through a series of selective ______ cleavages, similar to those described for insulin biosynthesis
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Gluconeogenesis is a pathway for ______ synthesis
Gluconeogenesis is a pathway for ______ synthesis
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Glucagon increases uptake of amino acids by the liver, resulting in increased availability of ______ for gluconeogenesis
Glucagon increases uptake of amino acids by the liver, resulting in increased availability of ______ for gluconeogenesis
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The islets of Langerhans release ______
The islets of Langerhans release ______
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Glucagon is considered one of the ______ hormones that oppose the actions of insulin.
Glucagon is considered one of the ______ hormones that oppose the actions of insulin.
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Glucagon binding results in activation of adenylyl cyclase in the plasma membrane, causing a rise in cAMP (the 'second messenger'), which, in turn, activates cAMP-dependent protein kinase and increases the ______ of specific enzymes or other proteins.
Glucagon binding results in activation of adenylyl cyclase in the plasma membrane, causing a rise in cAMP (the 'second messenger'), which, in turn, activates cAMP-dependent protein kinase and increases the ______ of specific enzymes or other proteins.
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The islets of Langerhans release ______
The islets of Langerhans release ______
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Glucagon acts to maintain blood glucose levels by activation of hepatic ______ and gluconeogenesis.
Glucagon acts to maintain blood glucose levels by activation of hepatic ______ and gluconeogenesis.
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Inhibition of gluconeogenesis resulting from hepatic metabolism of ethanol can lead to ______ of insulin-induced hypoglycemia.
Inhibition of gluconeogenesis resulting from hepatic metabolism of ethanol can lead to ______ of insulin-induced hypoglycemia.
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Glucagon is composed of 29 amino acids arranged in a single ______ chain.
Glucagon is composed of 29 amino acids arranged in a single ______ chain.
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Liver glycogen is an essential postprandial source of ______
Liver glycogen is an essential postprandial source of ______
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Gluconeogenesis is required to maintain blood glucose during ______ and ______
Gluconeogenesis is required to maintain blood glucose during ______ and ______
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Amino acids derived from a meal containing protein stimulate the release of both glucagon and ______.
Amino acids derived from a meal containing protein stimulate the release of both glucagon and ______.
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Epinephrine and norepinephrine stimulate the release of ______.
Epinephrine and norepinephrine stimulate the release of ______.
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Glucagon is a polypeptide hormone secreted by the α cells of the pancreatic islets of Langerhans. Glucagon, along with epinephrine, cortisol, and growth hormone (the 'counterregulatory hormones'), opposes many of the actions of insulin. Most importantly, glucagon acts to maintain blood glucose levels by activation of hepatic ______ and gluconeogenesis.
Glucagon is a polypeptide hormone secreted by the α cells of the pancreatic islets of Langerhans. Glucagon, along with epinephrine, cortisol, and growth hormone (the 'counterregulatory hormones'), opposes many of the actions of insulin. Most importantly, glucagon acts to maintain blood glucose levels by activation of hepatic ______ and gluconeogenesis.
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Glucagon is composed of 29 amino acids arranged in a single ______ chain.
Glucagon is composed of 29 amino acids arranged in a single ______ chain.
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Glucagon is synthesized as a large precursor molecule (preproglucagon) that is converted to glucagon through a series of selective ______ cleavages, similar to those described for insulin biosynthesis.
Glucagon is synthesized as a large precursor molecule (preproglucagon) that is converted to glucagon through a series of selective ______ cleavages, similar to those described for insulin biosynthesis.
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Glucagon secretion is increased by: 1. Low blood glucose: is the primary stimulus for glucagon release. 2. Amino acids: Amino acids derived from a meal containing protein stimulate the release of both glucagon and ______.
Glucagon secretion is increased by: 1. Low blood glucose: is the primary stimulus for glucagon release. 2. Amino acids: Amino acids derived from a meal containing protein stimulate the release of both glucagon and ______.
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The α cell is responsive to a variety of stimuli that signal actual or potential ______.
The α cell is responsive to a variety of stimuli that signal actual or potential ______.
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Glucagon increases uptake of amino acids by the liver, resulting in increased availability of ______ for gluconeogenesis.
Glucagon increases uptake of amino acids by the liver, resulting in increased availability of ______ for gluconeogenesis.
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Glucagon binding results in activation of adenylyl cyclase in the plasma membrane, causing a rise in cAMP (the 'second messenger'), which, in turn, activates cAMP-dependent protein kinase and increases the ______ of specific enzymes or other proteins.
Glucagon binding results in activation of adenylyl cyclase in the plasma membrane, causing a rise in cAMP (the 'second messenger'), which, in turn, activates cAMP-dependent protein kinase and increases the ______ of specific enzymes or other proteins.
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Liver glycogen can meet the needs for only ______ hrs in the absence of dietary intake of CHO.
Liver glycogen can meet the needs for only ______ hrs in the absence of dietary intake of CHO.
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Glucagon is considered one of the ______ hormones that oppose the actions of insulin.
Glucagon is considered one of the ______ hormones that oppose the actions of insulin.
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Glucagon secretion is significantly decreased by: 1. Elevated blood glucose 2. ______. Both substances are increased following ingestion of glucose or a carbohydrate-rich meal.
Glucagon secretion is significantly decreased by: 1. Elevated blood glucose 2. ______. Both substances are increased following ingestion of glucose or a carbohydrate-rich meal.
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Study Notes
Glucagon and Glucose Regulation
- Glucagon is a polypeptide hormone secreted by the α cells of the pancreatic islets of Langerhans.
- It opposes the actions of insulin and is a "counterregulatory hormone" along with epinephrine, cortisol, and growth hormone.
- Glucagon acts to maintain blood glucose levels by activating hepatic glycogenolysis and gluconeogenesis.
Structure and Synthesis of Glucagon
- Glucagon is composed of 29 amino acids arranged in a single polypeptide chain.
- Its amino acid sequence is the same in all mammalian species examined to date.
- Glucagon is synthesized as a large precursor molecule (preproglucagon) that is converted to glucagon through a series of selective proteolytic cleavages.
Regulation of Glucagon Secretion
- Glucagon secretion is increased by:
- Low blood glucose
- Amino acids derived from a meal containing protein
- Epinephrine and norepinephrine
- Glucagon secretion is decreased by:
- Elevated blood glucose
- Insulin
Metabolic Effects of Glucagon
- Effects on carbohydrate metabolism:
- Increases breakdown of liver glycogen
- Increases gluconeogenesis
- Effects on lipid metabolism:
- Activates lipolysis in adipose tissue
- Effects on protein metabolism:
- Increases uptake of amino acids by the liver
- Increases availability of carbon skeletons for gluconeogenesis
Mechanism of Action of Glucagon
- Glucagon binds to high-affinity G protein-coupled receptors on the cell membrane of hepatocytes.
- Activates adenylyl cyclase, leading to an increase in cAMP and phosphorylation of specific enzymes.
- Affects gene transcription.
Importance of Glucose Regulation
- Maintaining blood glucose levels between 70-110 mg/dL is crucial.
- Two main hormones involved in glucose regulation: insulin and glucagon.
Sources of Blood Glucose
- Between meals: hepatic glycogen
- During fasting and starvation: gluconeogenesis
Hypoglycemia
- Characterized by:
- Central nervous system symptoms
- Blood glucose level ≤ 40 mg/dl
- Symptoms resolved within minutes of glucose administration
- Types of hypoglycemia:
- Insulin-induced
- Postprandial
- Fasting
- Hypoglycemia due to alcohol intoxication in fasting individuals
Glucose-Regulatory Systems
- Two overlapping systems: islets of Langerhans and hypothalamic glucoreceptors.
- Respond to low blood glucose levels, triggering secretion of epinephrine, ACTH, and growth hormone.
Liver Glycogen and Gluconeogenesis
- Liver glycogen is an essential postprandial source of glucose.
- Gluconeogenesis is a pathway for glucose synthesis, required for maintaining blood glucose during fasting and starvation.
- Tissues requiring continuous glucose supply: brain, red blood cells, kidney medulla, lens, cornea, testes, and exercising muscles.
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Test your knowledge on the role of glucagon in glycogenolysis and blood glucose regulation.
