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Questions and Answers

Glucose-regulatory systems are activated by ______

hypoglycemia

The islets of Langerhans release ______

glucagon

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 ______

hypothalamic glucoreceptors Signup and view all the answers

ACTH increases ______ synthesis and secretion in the adrenal cortex

cortisol Signup and view all the answers

Liver glycogen is an essential postprandial source of ______

glucose Signup and view all the answers

Liver glycogen can meet the needs for only ______ hrs in the absence of dietary intake of CHO

8-10 Signup and view all the answers

Glycogen is stored in the ______ for short-term maintenance of blood glucose homeostasis

liver Signup and view all the answers

Glycogen is stored in the ______ as a source of energy

muscle Signup and view all the answers

Gluconeogenesis is required to maintain blood glucose during and

fasting, starvation Signup and view all the answers

Glucagon acts to maintain blood glucose levels by activation of hepatic ______ and gluconeogenesis.

glycogenolysis Signup and view all the answers

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.

proteolytic Signup and view all the answers

The α cell is responsive to a variety of stimuli that signal actual or potential ______.

hypoglycemia Signup and view all the answers

Amino acids derived from a meal containing protein stimulate the release of both glucagon and ______.

insulin Signup and view all the answers

Epinephrine and norepinephrine stimulate the release of ______.

glucagon Signup and view all the answers

Glucagon is composed of 29 amino acids arranged in a single ______ chain.

polypeptide Signup and view all the answers

Glucagon is considered one of the ______ hormones that oppose the actions of insulin.

counterregulatory Signup and view all the answers

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 ______.

glucagon Signup and view all the answers

Glucagon secretion is significantly decreased by: 1. Elevated blood glucose 2. ______. Both substances are increased following ingestion of glucose or a carbohydrate-rich meal.

Insulin Signup and view all the answers

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 ______.

gluconeogenesis Signup and view all the answers

Glucagon activates ______ in adipose tissue.

lipolysis Signup and view all the answers

Glucagon increases uptake of amino acids by the liver, resulting in increased availability of ______ for gluconeogenesis.

carbon skeletons Signup and view all the answers

Glucagon binds to high-affinity G protein-coupled receptors on the cell membrane of ______.

hepatocytes Signup and view all the answers

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.

phosphorylation Signup and view all the answers

Insulin and glucagon both play a role in maintaining ______.

glucose homeostasis Signup and view all the answers

Between meals, blood glucose is derived primarily from ______ glycogen.

hepatic Signup and view all the answers

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

glucagon Signup and view all the answers

Inhibition of gluconeogenesis resulting from hepatic metabolism of ethanol can lead to ______ of insulin-induced hypoglycemia.

reversal Signup and view all the answers

Glucose-regulatory systems are activated by ______

hypoglycemia Signup and view all the answers

The hypothalamic glucoreceptors respond to abnormally low concentrations of ______

blood glucose Signup and view all the answers

Liver glycogen is an essential postprandial source of ______

glucose Signup and view all the answers

Glycogen is stored in the ______ for short-term maintenance of blood glucose homeostasis

liver Signup and view all the answers

Gluconeogenesis is required to maintain blood glucose during and

fasting, starvation Signup and view all the answers

ACTH increases ______ synthesis and secretion in the adrenal cortex

cortisol Signup and view all the answers

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

proteolytic Signup and view all the answers

Gluconeogenesis is a pathway for ______ synthesis

glucose Signup and view all the answers

Glucagon increases uptake of amino acids by the liver, resulting in increased availability of ______ for gluconeogenesis

substrates Signup and view all the answers

The islets of Langerhans release ______

glucagon Signup and view all the answers

Glucagon is considered one of the ______ hormones that oppose the actions of insulin.

counterregulatory Signup and view all the answers

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.

phosphorylation Signup and view all the answers

The islets of Langerhans release ______

glucagon Signup and view all the answers

Glucagon acts to maintain blood glucose levels by activation of hepatic ______ and gluconeogenesis.

glycogenolysis Signup and view all the answers

Inhibition of gluconeogenesis resulting from hepatic metabolism of ethanol can lead to ______ of insulin-induced hypoglycemia.

reversal Signup and view all the answers

Glucagon is composed of 29 amino acids arranged in a single ______ chain.

polypeptide Signup and view all the answers

Liver glycogen is an essential postprandial source of ______

glucose Signup and view all the answers

Gluconeogenesis is required to maintain blood glucose during and

fasting, starvation Signup and view all the answers

Amino acids derived from a meal containing protein stimulate the release of both glucagon and ______.

insulin Signup and view all the answers

Epinephrine and norepinephrine stimulate the release of ______.

glucagon Signup and view all the answers

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.

glycogenolysis Signup and view all the answers

Glucagon is composed of 29 amino acids arranged in a single ______ chain.

polypeptide Signup and view all the answers

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.

proteolytic Signup and view all the answers

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 ______.

insulin Signup and view all the answers

The α cell is responsive to a variety of stimuli that signal actual or potential ______.

hypoglycemia Signup and view all the answers

Glucagon increases uptake of amino acids by the liver, resulting in increased availability of ______ for gluconeogenesis.

glucose Signup and view all the answers

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.

activity Signup and view all the answers

Liver glycogen can meet the needs for only ______ hrs in the absence of dietary intake of CHO.

24 Signup and view all the answers

Glucagon is considered one of the ______ hormones that oppose the actions of insulin.

counterregulatory Signup and view all the answers

Glucagon secretion is significantly decreased by: 1. Elevated blood glucose 2. ______. Both substances are increased following ingestion of glucose or a carbohydrate-rich meal.

insulin Signup and view all the answers

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.

مراجعة البايوكيم

Podcast Beta

Questions and Answers

Glucose-regulatory systems are activated by ______

The islets of Langerhans release ______

The hypothalamic glucoreceptors respond to abnormally low concentrations of ______

Epinephrine and adrenocorticotropic hormone (ACTH) can be released by the anterior pituitary in response to activation of the ______

ACTH increases ______ synthesis and secretion in the adrenal cortex

Liver glycogen is an essential postprandial source of ______

Liver glycogen can meet the needs for only ______ hrs in the absence of dietary intake of CHO

Glycogen is stored in the ______ for short-term maintenance of blood glucose homeostasis

Glycogen is stored in the ______ as a source of energy

Gluconeogenesis is required to maintain blood glucose during ______ and ______

Glucagon acts to maintain blood glucose levels by activation of hepatic ______ and gluconeogenesis.

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.

The α cell is responsive to a variety of stimuli that signal actual or potential ______.

Amino acids derived from a meal containing protein stimulate the release of both glucagon and ______.

Epinephrine and norepinephrine stimulate the release of ______.

Glucagon is composed of 29 amino acids arranged in a single ______ chain.

Glucagon is considered one of the ______ hormones that oppose the actions of insulin.

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 ______.

Glucagon secretion is significantly decreased by: 1. Elevated blood glucose 2. ______. Both substances are increased following ingestion of glucose or a carbohydrate-rich meal.

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 ______.

Glucagon activates ______ in adipose tissue.

Glucagon increases uptake of amino acids by the liver, resulting in increased availability of ______ for gluconeogenesis.

Glucagon binds to high-affinity G protein-coupled receptors on the cell membrane of ______.

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.

Insulin and glucagon both play a role in maintaining ______.

Between meals, blood glucose is derived primarily from ______ glycogen.

Inhibition of gluconeogenesis resulting from hepatic metabolism of ethanol can lead to ______ of insulin-induced hypoglycemia.

Glucose-regulatory systems are activated by ______

The hypothalamic glucoreceptors respond to abnormally low concentrations of ______

Liver glycogen is an essential postprandial source of ______

Glycogen is stored in the ______ for short-term maintenance of blood glucose homeostasis

Gluconeogenesis is required to maintain blood glucose during ______ and ______

ACTH increases ______ synthesis and secretion in the adrenal cortex

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

Gluconeogenesis is a pathway for ______ synthesis

Glucagon increases uptake of amino acids by the liver, resulting in increased availability of ______ for gluconeogenesis

The islets of Langerhans release ______

Glucagon is considered one of the ______ hormones that oppose the actions of insulin.

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.

The islets of Langerhans release ______

Glucagon acts to maintain blood glucose levels by activation of hepatic ______ and gluconeogenesis.

Inhibition of gluconeogenesis resulting from hepatic metabolism of ethanol can lead to ______ of insulin-induced hypoglycemia.

Glucagon is composed of 29 amino acids arranged in a single ______ chain.

Liver glycogen is an essential postprandial source of ______

Gluconeogenesis is required to maintain blood glucose during ______ and ______

Amino acids derived from a meal containing protein stimulate the release of both glucagon and ______.

Epinephrine and norepinephrine stimulate the release of ______.

Glucagon is composed of 29 amino acids arranged in a single ______ chain.

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 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 ______.

The α cell is responsive to a variety of stimuli that signal actual or potential ______.

Glucagon increases uptake of amino acids by the liver, resulting in increased availability of ______ for gluconeogenesis.

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.

Liver glycogen can meet the needs for only ______ hrs in the absence of dietary intake of CHO.

Glucagon is considered one of the ______ hormones that oppose the actions of insulin.

Glucagon secretion is significantly decreased by: 1. Elevated blood glucose 2. ______. Both substances are increased following ingestion of glucose or a carbohydrate-rich meal.

Study Notes

Glucagon and Glucose Regulation

Structure and Synthesis of Glucagon

Regulation of Glucagon Secretion

Metabolic Effects of Glucagon

Mechanism of Action of Glucagon

Importance of Glucose Regulation

Sources of Blood Glucose

Hypoglycemia

Glucose-Regulatory Systems

Liver Glycogen and Gluconeogenesis

Studying That Suits You

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