163b Metabolism II

Question 1

insulin

Answer 1

B cells in interior of islets of Lagerhans

Anabolic role

regulated by blood glucose levels - keeps glucose in narrow range

Question 2

glucagon

Answer 2

a cells in exterior of islets of langerhans

Question 3

glucagon-like peptide-1 (GLP-1)

Answer 3

L cells in jejunum in response to feeding

Question 4

Leptin

Answer 4

peptide from adipocytes

Question 5

Ghrelin

Answer 5

epsilon cells of inselts of langerhans and gut

fasting increases secretion

induces hunger and decreases E expenditure

Question 6

insulin synthesis

Answer 6

pre-proinsulin (A,B, C chains) –> insulin + C-peptide

stored in vesicles for quick release during meals

insulin t1/2 - 5 minutes –> measuring this isn’t useful, C-peptide has a much longer t1/2 - few hours

Question 7

regulation of insulin secretion

Answer 7

GLUT-2 brings in glucose
ATP is made
ATP-sensitive K channel shuts --> depolarization
Ca channels open
Vesicles are released

Question 8

how does insuling lower glucose?

Answer 8

myocytes and adipocytes increase glucose uptake (not in CNS - independent of insulin)

decreased glycogen breakdown/increased glycogen production in liver

decreased glucagon production

Question 9

what tissue is indep of insulin

Answer 9

brain, RBC, liver

Question 10

insulin receptor

Answer 10

membrane bound receptor –> tyrosine kinase receptors –> auto P –> IRS-1 P –> GLUT 4 insertion from vesicles (insulin dependent glucose transporter)

Question 11

hepatocyte - insulin effect on glucose metabolism

Answer 11

increases G1P –> glycogen synthesis via glycogen synthase

Question 12

insulin effect on adipose tissue

Answer 12

GLUT4 –> increased glucose –> increased fatty acids –> TG

Question 13

insulin and muscle

Answer 13

increased glycogen production and protein production

Question 14

what stimulates insulin secretion?

Answer 14

++
glucose
GLP-1
glucagon

–
inflammatory cytokines –> why post surgery people
NE

Question 15

glucagon effect on insulin secretion

Answer 15

stimulates insulin secretion

Question 16

glucagon action in liver cells

Answer 16

increase glycogen –> G1P via deactivation of glycogen synthase

increases gluconeogensis
—> acetyl CoA can’t be coverted back to pyruvate (Glucagon causes free fatty acids –> acetyl CoA –> ketone bodies)

Question 17

what causes glucagon secretion?

Answer 17

• glucose, insulin

Question 18

GLP-1 fxn

Answer 18

increases sensitivity of B cells to glucose –> increases insulin secretion in response to glucose

Question 19

leptin

Answer 19

adipocytes - in proportion to fat mass

sensor for fat storage/E reserves

induces satiety/E expenditure in hypothalamus

obesity –> defective leptin via resistance