Content from 9/8 to 9/12

Question 1

Insulin increases glucose transport into skeletal muscle cells by what?

Answer 1

Increasing translocation of GLUT-4 containing vesicles to the plasma membrane

Question 2

Which of the following statements about insulin receptor substrate (IRS) proteins is FALSE?

• IRS proteins are phosphorylated on tyrosine residues by the activated insulin receptor
• Tyrosine phosphorylation of IRS increases the enzymatic activity of the IRS protein
• Tyrosine-phosphorylated IRS acts as a docking protein to regulated downstream signaling factors
• The SH2 domain is located on the target protein and is involved in the recognition of phosphorylated tyrosine on the IRS
• Tyrosine phosphorylated IRS can propagate signaling to modulate numerous aspects of cell metabolism, such as glucose transport, glycogen synthesis, lipid synthesis, and protein synthesis.

Answer 2

Tyrosine phosphorylatoin of IRS increases the enzymatic activity of the IRS protein is FALSE!

Question 3

The Km of GLUT 4 is lower than the Km of GLUT 2 which means that glucose transport via GLUT 4 will saturate at what glucose concentration compared to GLUT 2?

Answer 3

At a lower glucose concentration that GLUT 2

Question 4

T/F - Blood flow in the capillary beds of skeletal muscle has a significant impact on glucose removal from the blood by regulating the delivery of glucose and insulin to the skeletal muscle cells?

Answer 4

TRUE

Question 5

T/F - Insulin can act on the smooth muscle cells in the arterioles of skeletal muscle tissue to activate nitric oxide synthase (eNOS) leading to nitric oxide production?

Answer 5

FALSE

Question 6

In which organs is the GLUT 2 glucose transporter isoform highly expressed?

Answer 6

Liver
Kidney
Intestines

Question 7

Which of the following statements about the transport of glucose across the endothelium of capillaries in skeletal muscle is/are TRUE?

• Enhanced blood flow to the capillaries will increase the diffusion of glucose into the extracellular space surrounding myocytes
• The transendothelial glucose transport is mediated by the GLUT 2 isoform
• The transendothelial glucose transport can be directly increased by insulin
• The amount of glucose delivered across the endothelium to the skeletal muscle cells influences the rate of glucose transport by the muscle cells

Answer 7

Enhanced blood flow to the capillaries will increase the diffusion of glucose into the extracellular space surrounding myocytes
The amount of glucose delivered across the enedothelium to the skeletal muscle cells influences the rate of glucose transport by the muscle cells

Question 8

What effect would an inhibitor of the serine kinase GSK-3beta have on insulin-resistant skeletal muscle?

Answer 8

Cause increased insulin-stimulated tyrosine phosphorylation of IRS-1
Cause increased insulin-stimulated glucose transport

Question 9

Oxidative stress can lead to insulin resistance in skeletal muscle. This is associated with decreased protein expression of…?

Answer 9

IRS

Question 10

Glucose delivery to skeletal muscle tissue is reduced in the Metabolic Syndrome by what 3 factors?

Answer 10

Reduced NO-stimulated vasodilation of arterioles
Less blood flow to the capillaries perfusing the muscle
Impaired insulin stimulation of eNOS in endothelial cells of arterioles

Question 11

Where is the primary site of dysfunction in the insulin signaling cascade in muscle cells?

Answer 11

IRS-1

Question 12

Which of the following are true regarding the production and consequences of ROS?
- ROS production can be increased by hyperglycemia and dyslipidemia
- ROS production takes place primarily in the motiochondria of the cell.
ROS can activate several serine kinases that negatively regulate IRS

Answer 12

All are TRUE

Question 13

T/F - Impairments in both the vascular delivery of glucose to the skeletal muscle cells and the transmembrane transport of glucose into the cells contribute to insulin resistance?

Answer 13

TRUE

Question 14

Which kinases can initiate serine phosphorylation that impairs the functionality of insulin signaling?

Answer 14

JNK
GSK-3beta
p38 MAPK

Question 15

T/F - Only IRS-1 is negatively affected by the up-regulatoin of PKCtheta activity due to elevated plasma FFAs?

Answer 15

FALSE

Question 16

T/F - A major consequence of defective insulin signaling in skeletal muscle is a reduction in the Km of glut-4 and diminished glucose transport activity?

Answer 16

FALSE

Question 17

T/F - Glucagon will inhibit insulin secretion from Beta cells while insulin can stimulate glucagon secretion from Alpha cells?

Answer 17

FALSE

Question 18

T/F - Based specifically on the anatomical positions of beta cells and alpha cells, and the direction of systemic circulation of factors in the blood, beta cells can exert more control on alpha cells than vice versa?

Answer 18

TRUE

Question 19

T/F - Hormones secreted from the pancreas are delivered to the hepatic portal circulation by the pancreatic duct?

Answer 19

FALSE

Question 20

T/F - After eating a meal PSNS nerve activity to the pancreas is increased. This will activate ACh receptors in the Beta cells and contribute to an increase in insulin secretion?

Answer 20

TRUE

Question 21

Put the following the steps in order from start to finish of the events associated with the sensing of glucose by the pancreatic Beta cells and the subsequent stimulation of insulin release:
Glucose enters the cell via GLUT-2
Mitochondrial metabolism yields ATP
Positive charge builds up causing depolarization of the cell
Insulin-containing vesicles move to the cell membrane and release insulin
Potassium channels are inhibited (closed) by ATP binding
Voltage-gated Ca2+ channels in the plasma membrane open

Answer 21

1. Glucose enters the cell via GLUT-2
2. Mitochondrial metabolism yields ATP
3. Potassium channels are inhibited (closed) by ATP binding
4. Positive charge builds up causing depolarization of the cell
5. Voltage-gated Ca2+ channels in the plasma membrane open
6. Insulin-containing vesicles move to the cell membrane and release insulin

Question 22

Low levels of glucose as sensed by the pancreas will result in which of the following?

• Sodium channel activation in the Alpha cell
• Quiescent Beta cells
• Glucagon release
• Beta cell depolarization

Answer 22

Sodium channel activation in the Alpha cell
Quiescent Beta cells
Glucagon releaes

Question 23

Which cells are expressed in the Islets of Langerhans?

Answer 23

Alpha cells
Beta cells
Delta cells
F cells

Question 24

High levels of plasma glucose will have which of the following effects on the Alpha cell?

• Increased glucose entry via transport using GLUT-1
• Activation of the Na+ channels and membrane depolarization
• Ca2+ channels will remain closed and there will be not change in intracellular Ca2+ levels
• Inhibition of glucagon release

Answer 24

Increased glucose entry via transport using GLUT-1
Ca2+ channels will remain closed and there will be no change in intracellular Ca2+ levels
Inhibition of glucagon release

Question 25

At the onset of exercise, SNS nerve activity to the pancreas is increased which is associated with decreased insulin secretion by Beta cells. Which of the following are involved in the process?

• Norepinephrine
• GPCRs
• Gq
• cAMP
• PKA

Answer 25

Norepi
GPCRs
cAMP
PKA