1What is secreted when blood glucose concentration increases?
Insulin
2What cells in the pancreas secrete insulin?
Beta cells
3Describe the basic structure of insulin.
Two peptide chains joined by three disulfide bridges
4Describe how insulin is synthesised.
Prepoisnulin —> proinsulin —> activated insulin
5Where in the cell does proinsulin mature into active insulin?
Golgi apparatus
6What is the co factor for insulin synthesis?
Zinc
7How does glucose enter beta cells?
Via GLUT2 transporter proteins
8What GLUT transported is glucose dependent?
GLUT2
9What enzyme converts glucose into glucose 6 phosphate?
Hexokinase /Glucokinase
10C peptide is a product that indicates level of what hormone?
Insulin
11How is glucose stored in cells?
As a hexamer
12What enzyme acts as the glucose sensor for insulin secretion?
Glucokinase
13Does glucokinase have a high or low Km and what effect does this have?
High Km, high concentrations of glucose are required for insulin secretion to occur
14Influx of what ion triggers insulin secretion?
Calcium
15Briefly describe how is insulin is secreted from beta cells starting with increased glucose concentration.
High glucose —> Increase ATP:ADP ratio —> ATP dependent potassium channels close —→ membrane depolarisation —> Caclium channels open —> Calcium ion influx —> insulin secretion
16Describe what channels are open during sub stimulatory glucose concentrations and what happens when they become stimulatory?
When glucose concentrations are high ATP dependent potassium channels close causing depolarisation which triggers calcium channels to open
17In how many phases does pancreatic beta cells release insulin in?
Two phases
18Describe the first phase in the release of insulin.
Rapidly triggered in response to increased blood glucose levels
19Describe the second phase in the release of insulin.
Slow and sustained release of insulin from vesicles
20What are other signals that can stimulate insulin release?
Amino acids; GLP1; GIP; Fatty acids; CCK
21How do amino acids stimulate insulin release?
Enter through transporters to depolarise membrane causing calcium channels to open
22What is excessive basal insulin secretion linked to?
Insulin resistance
23What occurs to the insulin receptor when blood glucose concentration is low?
It is inactive
24How does the insulin receptor work when blood glucose concentration increases?
Insulin receptor substrate binds to insulin receptor; Insulin receptor is autophosphorylated via tyrosine residues; IRS is then phsophrylated
25What processes occur when blood glucose conetration decreases?
Gluconeogenesis; Glycogenolysis; Lipolysis
26What precursor is glucagon made from?
Proglucagon
27How do glucagon and adrenaline work via second messenger?
Activates enzyme that converts AMP into cAMP
28What are some insulin counter regulatory hormones?
Cortisol; Growth Hormone; Adrenaline; Glucagon
29What are corticosteroids synthesised from?
Cholesterol
30What regulates the secretion of corticosteroids?
HPA axis
31What is the main role of cortisol?
Resists stress and inflammation and helps maintain blood pressure
32In what conditions cause cortisol to be increased?
Low blood glucose conditions
33Describe the metabolic effects of cortisol.
In the liver it enhances gluconeogeneiss; In the muscle it inhibits glucose uptake and stimulates protein degradation
34What stimulates the release of growth hormone?
Growth hormone releasing hormone (GHRH)
35What inhibits the release of growth hormone?
Somatostatin
36How does the growth hormone act?
Anatgonist of insulin causing blood glucose concentrations to rise
37What secretes growth hormone?
Anterior pituitary gland
38Describe the incretin effect.
Oral glucose has a greater insulin response than IV glucose
39What cells secrete GLP1?
L cells in the small intestine
40What cells secrete GIP?
K cells in the small intestine
41In what conditions is GLP1 and GIP secreted in?
Secretion in response to ingestion of a meal or glucose - high blood glucose
42Describe the proteolytic degradation of GLP1 and GIP.
DPP4 breaks down GIP and GLP1
43What type of receptors doe GLP1 and GIP act on?
G coupled protein receptors