Exam 5: The Endocrine Pancreas and Carbohydrate Metabolism Flashcards
How is GLUT4 regulated?
Insulin
Where is a GLUT4 transporter not located?
Brain
Liver
How does insulin circulate?
Mostly unbound
What are the functions of insulin?
Anabolic
Decrease blood glucose
Facilitates tissue uptake of glucose, amino acids, fatty acids, K, Mg, and P
Stimulates glycogen synthesis, lipogenesis, protein synthesis and storage
Inhibits glycogenolysis, lipolysis, and protein catabolism
What does insulin receptor binding do?
Activates some intracellular enzymes and inactivates others
How quickly does the 1st insulin receptor binding result?
Within seconds
What happens after the 1st insulin receptor binding?
80% of body’s cells increase glucose uptake (muscle, adipose, not most neurons)
Immediate phosphorylation of glucose
Where is insulin not required the most for glucose transport?
Neurons
What are additional insulin binding effects?
Increase cell membrane permeability to amino acids, K, and P
Intracellular flow, so it will decrease blood concentration
Slower insulin effect, 10-15 min, which will increase or decrease activity level of many intracellular enymes
What does muscle do in the presence of insulin?
Absorbs glucose for immediate energy
Synthesizes glycogen for use later
What does the liver do in the presence of insulin?
Stimulates glycogenesis
Inhibits glycogenolysis
What does insulin on liver CHOs promote?
Glucose storage in the form of glycogen
What happens when insulin enhances the liver’s glucose uptake and retention?
Increase activity of glucokinase
Decrease activity of phosphatase
What happens when insulin activates glycogen synthesis enzymes?
Increase glycogen synthase
What happens when insulin inhibits the breakdown of glycogen?
Decrease activity of liver phosphorylase
What happens to the liver in the absence of insulin?
Releases glucose into the circulating blood
What happens with the promotion of fat synthesis and storage by insulin?
Carbohydrate excess (promotion of fatty acid synthesis in hepatocytes)
Promotes FA transport to and storage in adipose tissue
Inhibits lipolysis
What does lipoprotien lipase (activated by insulin and FA) allow?
Storage of TG in adipose tissue
What occurs with lipid and insulin deficiency?
Lipolysis
Ketone formation in liver
What does insulin promote for protein?
Protein synthesis and storage
What does the promotion of protein synthesis and storage by insulin do?
Stimulates transport of amino acids into cells, including muscle
Inhibits protein catabolism
Decrease hepatic gluconeogenesis
What does the stimulation of transport of amino acids do?
Increase translation of mRNA
What is the primary regulator of insulin release?
Blood glucose
How does glucose enter β cells?
GLUT-2
What is glucose proportional to?
Blood glucose concentration
What does the rate of glucose entry control?
Excytosis of insulin vesicles
What does high BG do to insulin secretion?
Increases it
What does low BG do to insulin secretion?
Decreases it
What are the functions of glucagon?
Anti-insulin/diabetogenic Rapid acting Hepatic glycogenolysis Hepatic gluconeogenesis Lipolysis
What does decreased glucose do to glucagon secretion?
Increases it
What does increased glucose do to glucagon secretion?
Decreases it
What do amino acids do in glucagon regulation?
Stimulate glucagon secretion
