Insulin Pathophysi

Question 1

insulin receptor structure

Answer 1

dimer of 2 a-domains and 2 b-domains that are disulfide cross-linked

Question 2

role of A subunits on insulin receptor

Answer 2

regulatory unit of the receptor represses the catalytic activity of beta subunit repression is relieved by insulin binding

Question 3

role of B subunits on insulin receptor

Answer 3

contain the tyrosine kinase catalytic domains for autophosphorylation so that it can bind insulin receptor substrate (IRS)

Question 4

effects of insulin on the liver

Answer 4

inhibits glycogenolysis, ketogenesis, and gluconeogenesis
stimulates glycogen synthesis and triglyceride synthesis

Question 5

effects of insulin on skeletal muscle

Answer 5

stimulates glucose transport and amino acid transport

Question 6

effects of insulin on adipose tissue

Answer 6

stimulates glucose transport and amino acid transport

Question 7

PI3K (Phosphatidylinositol 3-kinase)

Answer 7

most prominent protein recruited by IRS in insulin receptor signaling

Question 8

lipogenesis

Answer 8

glucose stored in adipocytes

Question 9

glycolysis

Answer 9

utilization of glucose for fuel

Question 10

glycogen synthesis

Answer 10

storage of glucose

Question 11

gluconeogenesis

Answer 11

export of glucose

Question 12

glucose disposal (uptake into tissue) during fasting state

Answer 12

not secreting insulin
75% is insulin non-insulin-dependent: liver, GI, brain
25% is insulin-dependent in skeletal muscle
glucagon is secreted to prevent hypoglycemia

Question 13

glucose disposal (uptake into tissues during fed state)

Answer 13

80-85% is insulin-dependent in skeletal muscle
4-5% is insulin-dependent in adipose tissue
glucagon secretion is inhibited
insulin inhibits release of FFA from adipose tissue

Question 14

decreased serum free fatty acids (FFA)

Answer 14

enhances insulin action on skeletal muscle
reduces hepatic glucose production

Question 15

glucose transporters

Answer 15

GLUT 1
GLUT 2
GLUT 3
GLUT 4

Question 16

GLUT 1

Answer 16

Km = 1 to 2 mM
constitutive
widely expressed, may be found in B cells

Question 17

GLUT 2

Answer 17

Km = 15-20 mM (glucose concentration has to be high for glucose transport to occur)
constitutive
found in B-cells

Question 18

GLUT 3

Answer 18

Km < 1 mM (will transport glucose at very low glucose concentrations)
constitutive
found in neurons

Question 19

GLUT 4

Answer 19

Km = 5 mM
insulin induced
found in skeletal muscle

Question 20

B-cells

Answer 20

found in the pancreas
secrete insulin and amylin

Question 21

endocrine B-cells

Answer 21

secretes into the blood stream

Question 22

exocrine B-cells

Answer 22

secretes into the small intestine

Question 23

glucagon

Answer 23

stimulates glycogen breakdown and increase blood glucose secreted by a cells of pancreas

Question 24

somatostatin

Answer 24

general inhibitor of secretion of a and B cells
secreted by D-cells

Question 25

insulin

Answer 25

stimulates uptake and utilization of glucose
secreted by B-cells

Question 26

amylin

Answer 26

co-secreted with insulin
slows gastric emptying
decreases food intake
inhibits glucagon secretion
secreted by B-cells

Question 27

insulin processing

Answer 27

synthesized as a single peptide and deposited in secretory granules
in secretor granules, insulin is cleaves to A and B chains, and C (connecting) peptides by proconvertase

Question 28

Zn role in insulin

Answer 28

packs insulin together in tight structures