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Copy of Untitled Prezi

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nada mansour

on 17 December 2014

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Transcript of Copy of Untitled Prezi

Glucagon
Introduction
- Polypeptide hormone secreted by the
Þ
-cells of the islets of Langerhans.
-
Composed
of 29 amino acids arranged in a single polypeptide chain.
-
Synthesized
as a non-active single polypeptide chain & its activated through t series of selective proteolysis like insulin.
- It works beside epinephrine, nor-epinephrine, growth hormone, cortisol during stress situation (whenever fuel is needed in abundance) therefore it opposes= counter regulates the insulin's action.
-
Functions
: maintain of blood glucose level by enhancing: glycogenolysis & gluconeogenesis
Simulations of glucagon secretion:-
1- low blood glucose :- its the PRIMARY stimuli. this is clear during over night or prolonged fasting the glucagon's prevents
hypoglycemia.

2-

Amino acids: - derived from meals stimulate BOTH insulin & glucagon the later prevents hypoglycimia that would resulted from insulin amount that would results after a protein meal.
3- Epinephrine & nor-epinephrine:- levels of one or both hormones stimulate glucagon's release. therefore during stress, trauma, severe muscular exercises glucagon will while insulin is
Inhibition of glucagon secretion:-
*
This significantly occurred after glucose level and insulin which happens after glucose rich meal or carbohydrate.
Metabolic effects of glucagon:-
1-
Effects on carbohydrate metabolism
:- intravenous administration of glucagon immediate in blood glucose which came as result of breakdown of liver (NOT MUSCLES) glycogen + gluconeogenesis.

2-
Effects on lipid metabolism
:- it lipolysis in adipose. the F.A release as a consequences taken up by the liver and oxidized to acetyle coA.

3-
Effects on protein metabolism
:- glucagon uptake of amino acids by the liver carbon skeleton for gluconeogenesis & plasma level of amino acids.
Mechanism of action of glucagon:-
1- It binds to a high affinity
receptors
on the cell membrane of hepatocytes. Glucagon's receptors are different from these for insulin or epinephrine.
2- Binding of glucagon to its receptors results in activation of adenelyte cyclase cAMP (second massenger) protein kinase & phosphorylation of certain enzymes to activate them to affect the KEY enzymes involved in carbohydrate & lipid metabolism.

Glycogeolysis
Ketogenesis
Gluconeogenesis

Uptake of amino acids
lipolysis

Glycogenesis
Full transcript