Insulin, Glucagon and Diabetes Flashcards
There are two major types of tissue that compose the pancreas
The Acini, which secrete digestive juices into the duodenum
The Islets of Langerhans, which secrete insulin and glucagon directly into the blood
The pancreas contains between 1 and 2 million pancreatic islets which are organized _____
around small capillaries.
The islets contain three major types of cells that differ in their morphological and staining characteristics
Alpha Cells- Secrete glucagon (about 25% of islet)
Beta Cells- Secrete insulin and amylin (about 60% of islet)
Delta Cells- Secrete somatostatin
Insulin is a small protein hormone that is associated with “_______.”
energy abundance
What is insulin composed of?
Two amino acid chains that are connected to each other by disulfide linkages
Explain the synthesis of Insulin
Slide 11
The primary controller of insulin secretion is the
glucose concentration in the blood.
Beta cells contain a large number of membrane _____ which permit an influx of glucose at a rate proportional to the blood glucose concentration
glucose transporters (GLUT2)
Glucose-6-phosphate is then oxidized into
ATP
ATP inhibits membrane Potassium leak channels, which causes the cell to _____
depolarize
What, in addition to ATP, can inhibit the K+ channel, increasing insulin secretion?
Sulfonylurea drugs
Normal fasting level of blood glucose
80 to 90 mg/100 mL
As the blood glucose concentration rises above ____, secretion of insulin rises rapidly (10-fold within 3-5 minutes)
100
After insulin is secreted, it circulates almost entirely ____ and free in the plasma.
unbound
To initiate its effects on target cells, insulin first needs to do what?
bind with and activate a membrane receptor protein (which we call the Insulin Receptor)
Insulin receptors are made up of 2 parts - what are they?
2 extracellular alpha subunits and two membrane-bound beta subunits (connected by disulfide bonds)
Proinsulin is made of
three peptide chains: A, B, and C
In the golgi apparatus, most of the Proinsulin is cleaved at two sites to form _____, which is composed of disulfide-connected A and B chains
Insulin
The C chain is also called “the connecting peptide,” or _____
C Peptide
These IRS enzymes are responsible for ____
regulating the intracellular effects of insulin.
Three locations of rapid uptake of glucose
muscles, adipose tissue, and the liver.
T/F One of the most important effects of insulin is to cause most of the glucose absorbed after a meal (up to 60%) to be rapidly stored in the liver in the form of glycogen.
T
The ___ does not require insulin in order to utilize glucose
brain
Excess glucose is converted into ___
fatty acids (lipogenesis)
