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Flashcards in hormonal regulation of metabolism Deck (37):
1

effect of pancreatic insulinoma

increases insulin production, leads to fasting hypoglycemia

2

action of insulin

stimulates glucose uptake into tissues for use and storage

3

steps of insulin synthesis

made in RER of pancreatic b-cells
- initial form is preproinsulin, this is converted to proinsulin by cleaving the signal sequence
- proinsulin is transported to golgi
- proinsulin is converted to insulin by cleaving C-peptide
- end product = a chain and b chain linked by 2 disulfide bonds

4

describe the biphasic release of insulin

initially, insulin levels increase rapidly bc the insulin that was stored in b-cell secretory vesicles is released, sustained insulin response is from de novo synthesis and is more steady

5

typical insulin level at fasting blood glucose

usually 1

6

to what blood glucose level can insulin accommodate

insulin will continue to rise with blood glucose until about 300 mg/dL, past that insulin will remain steady even if glucose continues to rise

7

stimulatory effects of insulin (5)

uptake of glucose into (some) tissues
use of glucose
fat synthesis
fat storage
general protein synthesis

8

inhibitor effects of insulin (2)

glycogen breakdown
fat mobilization

9

major glucose transporter in muscle and adipocytes

GLUT-4

10

effect of insulin on the liver

stimulates use of glucose (like glycogen synthesis and glycolysis), but does NOT direct glucose uptake

11

what is the action of glucokinase in the liver?

insulin stimulates glucokinase in the liver, action of glucose kinase is to phosphorylate glucose to effectively trap it in the liver

12

which type of cells discussed use insulin-indpendent methods of glucose uptake?

neural cells

13

normal vs. abnormal response to glucose tolerance test

normal- rapid rise and drop in blood glucose, hypoglycemia may result, blood glucose should return to around fasting by 3 hrs
abnormal- higher and more sustained increase in blood glucose level

14

glycemic index

area under 2 hr glucose curve after feeding a 50 g test CHO portion

15

what is the "standard for GI"?

white bread, GI = 1.0

16

ways to increase GI

refine, make more simple sugars

17

ways to decrease GI

add fiber, fat, protein

18

glucagon source and structure

pancreatic a-cells
proglucagon = 160 aa
mature form = 29 aa
short half life in plasma

19

what will stimulate glucagon secretion? (4)

-low blood glucose
- epinephrine
- cortisol
- exhaustive exercise

20

what inhibits glucagon secretion? (2)

high insulin
high glucose

21

what does glucagon act on directly?

liver and adipocytes

22

what can glucagon not act on directly?

muscle, bc it lacks glucagon receptors

23

what does glucagon stimulate? (3)

- glycogenolysis in liver
- breakdown of TAG in adipocytes to fatty acids and glycerol
- breakdown of protein in muscle to provide aa for gluconeogenesis

24

what does glucagon inhibit? (2)

glycogen synthesis
fat storage

25

what hormone stimulates glycogen mobilization in muscle?

epinephrine

26

what is the result of glucogenolysis in muscle?

glucose is phosphorylated and muscle lacks the phosphatase needed to remove phosphate, so it remains in the muscle where it is used for energy. Byproducts of glucose metabolism (lactate and pyruvate) can be used in gluconeogenesis

27

which tissues are acted on by epinephrine?

liver, adipocytes, muscle

28

what is the effect of epinephrine on glucagon? insulin?

glucagon- stimulates release
insulin- inhibits release

29

which tissue lacks glucagon receptors?

muscle

30

which tissues are acted on by glucagon?

liver, adipocytes

31

what signaling pathway is common for epinephrine and glucagon?

both use GaS, increase cAMP and activate protein kinase a

32

what is activated by protein kinase A?
what is inactivated by protein kinase A?

activated- glycogen phosphorylase, lipase
inactivated- glycogen synthase, fatty acid synthesis

33

how does cortisol stimulate fuel mobilization?

binds to intracellular receptors and regulates gene transcription

34

what is unique about the action of cortisol?

it is released in times of stress, but it stimulates glycogen synthesis NOT breakdown

35

insulin vs protein kinase a

insulin will activate serine/threonine phosphatase that will oppose the actions of PKA- will turn on glycogen synthase/fatty acid synthesis and turn off glycogen phosphorylase and lipase

36

describe hormone changes after protein only meal

- increase glucagon- amino acids alone stimulate glucagon release bc glucagon will stimulate amino acid degradation and gluconeogenesis in the liver
- increase insulin slightly to promote uptake of amino acids into muscle and stimulate protein synthesis

37

in "mixed" meals, which 2 aa in particular, will stimulate insulin release in response to glucose?

lysine
arginine