Two major cell types that express the GLUT2 transporter.
hepatocytes (liver cells) and β cells of the pancreas
Hepatocytes and β cells of the pancreas express GLUT2 because they...
have unique mechanisms for measuring and controlling blood glucose levels
The amount of glucose entering cells expressing GLUT2 is _______ over the normal (physiological) range of blood glucose levels.
linear (because it is low affinity)
GLUT3 transports ______ levels of glucose, even at _______ blood glucose concentration levels because it is expressed in cells of the ________.
high; low; nervous system
Enzymes with small values for Km will reach Vmax at...
lower substrate concentrations
Enzymes with high values for Km will reach Vmax at...
higher substrate concentrations.
Your brain doesn't know _____________, but the β cells in your pancreas do.
what your blood glucose levels are
After a meal, the linear relationship between glucose entering hepatocytes and pancreatic β cells and blood glucose levels allows...
the β cells to detect an increase in blood glucose and release insulin into the blood.
Increased uptake of glucose into β cells via __________ results in increased glucose metabolism by...
GLUT2; oxidation via glycolysis and the TCA cycle (thus increased ATP)
An increase in ATP due to increased glucose uptake by β cells initiates closing of __________, which leads to _____________.
K+ channels; membrane depolarization
Membrane depolarization due to increased ATP production (due t increased glucose uptake by β cells) is associated with the opening of ________________, allowing...
Ca++ channels; an increase in cellular Ca+ levels
Increased intracellular Ca+ levels induces...
translocation of insulin-containing vacuoles to the plasma membrane to be released into the blood stream by exocytosis
Class of drugs used to lower blood glucose.
How do Sulfonylureas lower blood glucose?
they increase β cell insulin release by binding to and blocking the ATP-sensitive K+ channel, mimicking the increase in β cell ATP levels
What are the 3 ways that insulin lowers blood glucose?
1. increasing glucose uptake into "insulin responsive tissues"
2. increasing the activity of pathways of glucose utilization
3. decreasing the activity of pathways of glucose production
What are the 2 primary and 1 somewhat insulin responsive tissues?
muscle and adipose tissues; sometimes heart tissue
Insulin lowers blood glucose by driving glucose into...
muscle, adipose tissue, and sometimes heart tissue
Insulin mobilizes _________ to the plasma membranes of ________ and _______.
GLUT4; muscle; adipose tissue
In GLUT4 transports, insulin binds to the ________, inducing _______ and increased _______ activity.
insulin receptor; dimerization; RTK
The insulin receptor kinase activity phosphorylates and activates ___________.
Insulin receptor substrate (IRS)
Insulin receptor substrate activates _____.
When PI3K s activated by insulin receptor substrate, ________ and _________ are activated.
αPKB and Atk/PKB
The combined signal from αPKC and Akt/PKB activates.....
translocation of GLUT4 to the plasma membrane
hen GLUT4 is translocated to the plasma membrane, ________________ is increased, subsequently...
glucose uptake; decreasing blood glucose levels, causing insulin levels to decrease and GLUT4 to be recycled
Endocrine disorder characterized by absolute or relative lack of insulin; persistently elevated glucose.
Describe the β cell function in Type I Diabetes and its treatment.
NO FUNCTIONAL β cells; daily insulin injections for life
Describe the β cell function of Type II Diabetes and its treatment.
Some variable β cell function; diet, weight loss, oral hypoglycemics
With a glucose tolerance test, the 4 steps are...
1. 12 hour fast
2. intravenous glucose infusion
3. assess blood glucose levels at 0,30,60,90,120 min after infusion
4. compare to general ranges of blood glucose
In healthy individuals, blood glucose levels are...
maintained within a VERY TIGHT range
On the glucose tolerance test, a healthy individual had a _______ fasting blood glucose level and a _________ in response to glucose infusion; subsequently, their blood glucose level __________.
low; moderate rise; returned to normal
On the glucose tolerance test, a diabetes type I individual had _______ fasting blood glucose level and ________ blood insulin; subsequently, their blood glucose level __________.
an elevated; no detectable; does not decline
On the glucose tolerance test, a diabetes type II individual had _______ fasting blood glucose level and a _________ in response to glucose infusion; subsequently, their blood glucose level __________.
elevated; modest induction of blood insulin; does not significantly decline
On the glucose tolerance test, an obese individual had _______ fasting blood glucose level and _________ in response to glucose infusion; subsequently, their blood glucose level __________.
elevated; extremely high insulin levels; does not decline
Obese individuals have insulin but their glucose levels cannot return to normal; this is _____________.
peripheral insulin resistance
___________, which is non-digestible, reduces the caloric density of feed.
Fiber reduces caloric density of feed by....
slowing glucose uptake from the gut
Peripheral insulin resistance (from obesity) is due to the fact that adipocytes produce ________, which bind and activate signaling pathway that interfere with ______, and ultimately....
adipokines; insulin receptor signaling; reduce insulin dependent glucose uptake in fat and muscle cells.
Glycogen is stored in...
the muscle and liver
_______ is the body's source of glucose during a fast.
_________ is the body' source of glucose for contraction within a cell.
Although glycogen stores are a relatively small percent of total body energy,...
glycogen storage diseases are fatal, usually in the early postnatal period
Insulin activates ________ vis _______.
glycogen synthase; protein phosphatase 1
Following a meal, increased blood glucose levels cause _____________, which then bind to...
increased insulin release from the pancreas; liver cell insulin receptors.
Insulin receptor mediated signaling in the liver activates ___________, which in turn ________ and activates __________.
protein phosphatase; dephosphorylates; glycogen synthase
In addition to activating glycogen synthesis, protein phosphatase...
dephosphorylates and deactivates glycogen phosphorylase, the enzyme that degrades glycogen
Glycogen branching enzyme deficiency is a ______ disorder in Quarter Horses and always...
autosomal recessive; results in death
The first line of defense in maintaining blood glucose levels is the _________.
breakdown of liver glycogen
The fall in blood glucose is detected by __________, which release ________.
α cells of the pancreas; glucagon
The function of the hormone glucagon is to...
increase blood glucose levels by mobilizing glucose stored in the liver as glycogen.
The second line of defense in maintaining blood glucose levels during a long-term fast is ________.
The primary target tissue of the hormone glucagon is _______.
Glucagon's main mechanism of action is activation of ________________ of __________ and release of ______.
GPR-mediated activation of protein kinase A (PKA); Ca+
Glucagon binds to _______ and activates _______, which phosphorylates and activates _______, which degrades glycogen.