46 Questions
What process is activated by insulin in the liver?
Synthesis of glycogen
What is the effect of insulin on glycogenolysis in the liver?
It is inhibited
What type of bonds link the two polypeptide chains in insulin?
Disulphide bridges
What is the effect of insulin on triglyceride utilisation in muscle?
It is activated
What is the effect of cortisol on glucose metabolism in the liver?
It increases gluconeogenesis
What is the effect of insulin on glucose uptake in adipose tissue?
It is activated
What is the effect of adrenaline on glucose metabolism in muscle?
It decreases glucose uptake
What is the effect of insulin on lipolysis in adipose tissue?
It is inhibited
How many disulphide bridges are present in the insulin molecule?
Three
What is unique about the structure of insulin?
It has two polypeptide chains linked by disulphide bridges
What is the initial form of insulin synthesized on ribosomes?
Pre-proinsulin
What is the function of the pre-part in pre-proinsulin?
To ensure the newly synthesized protein enters the endoplasmic reticulum
What is removed from the pre-proinsulin molecule once it enters the endoplasmic reticulum?
The signal peptide
What is the resulting molecule after the signal peptide is removed?
Proinsulin
What is the function of proinsulin folding?
To ensure correct alignment of the cysteine residues
Where is proinsulin transported to after folding?
Golgi apparatus
What occurs in the storage vesicles?
Proteolysis
What is the function of C-peptide in the plasma?
To serve as a marker of endogenous insulin release
What is released during insulin secretion?
The entire contents of the storage granules
What is the purpose of measuring plasma C-peptide levels in patients receiving insulin?
To monitor endogenous insulin secretion
What is the form in which insulin is stored in -cell storage granules?
Zinc-insulin complex
What happens to insulin when it is released from the -cell storage granules?
It dissolves in the plasma and circulates as a free hormone
What is the primary function of insulin in the body?
To clear absorbed nutrients from the blood following a meal
What are the major target tissues for insulin action?
Liver, skeletal muscle, and adipose tissue
What is the effect of insulin on carbohydrate metabolism?
It promotes glucose uptake in target tissues
How does insulin interact with its target cells?
Through binding to receptors on the surface of target cells
What is the time frame in which insulin's effects occur?
Sec/hr
What is the result of insulin's action on its target tissues?
Anabolic effects
What is the primary structure of glucagon?
A single chain polypeptide hormone
What is the effect of insulin on glucose transport in adipose tissue and skeletal muscle?
Increase glucose transport
What happens to the pre-proglucagon molecule during post-translational processing?
It is converted into the biologically active molecule
What is the effect of insulin on glycogenolysis in liver and muscle?
Decrease glycogenolysis
What is the effect of insulin on lipolysis in adipose tissue?
Decrease lipolysis
What is the effect of glucagon on glycogenolysis in the liver?
It increases glycogenolysis
What type of receptor does glucagon bind to?
A G protein-coupled receptor
What is the effect of insulin on glycolysis in liver and adipose tissue?
Increase glycolysis
What is the effect of glucagon on lipolysis in adipose tissue?
It increases lipolysis
What is the effect of insulin on protein synthesis in liver, muscle, and adipose tissue?
Increase protein synthesis
What is the effect of glucagon on gluconeogenesis in the liver?
It increases gluconeogenesis
What is the effect of insulin on lipoprotein lipase activity in the capillary bed of tissues such as adipose tissue?
Increase lipoprotein lipase activity
Which of the following hormones stimulates insulin secretion?
Acetyl choline
What is the effect of glucagon on ketogenesis in the liver?
It increases ketogenesis
What is the primary factor that increases the rate of glucagon secretion?
A decrease in blood glucose concentration
What is the primary function of insulin in the body?
To lower blood glucose concentration
What is the effect of insulin on gluconeogenesis in liver?
Decrease gluconeogenesis
What enzyme is activated by the binding of glucagon to its receptor?
Adenylate cyclase
Understand how insulin is synthesized and processed in the endoplasmic reticulum. Learn about pre-proinsulin, signal peptides, and proinsulin folding. Test your knowledge of insulin synthesis and its mechanisms.
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