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Flashcards in Intro to Metabolism Deck (23):

What happens when glucose levels are low?

The liver can produce glucose and keto bodies


Function of insulin?

promote the synthesis of macromolecules


Function of glucagon and catecholamines?

break down molecules and provide ATP


Function of the AMPK pathway?

Sense low ATP levels and then restore ATP levels


What is the mecahnism of the AMPK pathway?

Stimulate catabolic pathways that generate ATP, inhibit anabolic pathways that consume ATP


Function of mTOR pathway?

sense amino acid availability, regulate cell growth and cell proliferation, regulate tissue and organ growth
** very important for regulating the cell cycle **


Mechanism of mTOR pathway?

stimulate protein synthesis, stimulate ribosomal bigenisis, inhibit autography


Function of glucagon

(1) stimulating the liver to break down glycogen to be released into the blood as glucose
(2) activating gluconeogenesis, the conversion of amino acids into glucose
(3) breaking down stored fat (TAGs) into fatty acids for use as fuel by cells


Why is C-peptide a good indicator of insulin production?

Because of its longer half life; c-peptide levels are used to differentiate the cause of high insulin in patients


Function of insulin

(1) increase glucose uptake
(2) glycogen (glucose polymer) synthesis in the liver and muscle
(3) decrease of glucose in the liver


Effects of insulin signaling through receptor tyrosine kinasee

(1) alter protein and enzyme activity (increased GLUT 4 movement to plasma)
(2) dephosphorylation of enzymes (activation of glycogen synthase)
- increase glucose uptake,, glycogen synthesis (in liver)


Effect of coffee and tea

Coffee and tea keep activation of glucagon and epinphrine pathways


Fate of glucose-6-phosphate?

(1) glycogen synthesis
(2) glycolysis


Two signaling pathways of insulin?

(1) ras-dependent signaling (via RAS) -> alterations in gene transcription
(2) ras-independent signaling (via PKB) -> alterations in protein and enzyme activity, dephosphorylation of enzymes


Describe glucagon and epinephrine binding to G-protein coupled receptor

activate G-protein -> which activates adenylyl cyclase -> converts ATP to cAMP -> cAMP activates PKA -> PKA phosphorylates protein


How are epinephrine and glucagon different?

Epinephrine responds to stress; glucagon responds to low blood sugar; muscle has epinephrine receptors but the liver has receptors for both epinephrine and glucagon


Effect of caffeine, theophlline, and other members of the methyxanthine group?

Inhibit phosphodiesterase, leading to increased cellular levels of cAMP


What does phosphodiesterase do?

A phosphodiesterase (PDE) is any enzyme that breaks a phosphodiester bond. (found in cAMP)


One more time, AMPK pathway - details

(1) stimulated by AMP (AMP comes from ADP after being catalyzed by adenylate kinase)
(2) AMPK promotes catabolism and inhibits ATP consumption
(3) AMPK is inhibited by ATP


Role of mTOR and AMPK

act as nutrient and energy sensors and regulate metabolism in conjunction with hormones


Intertissue relationships during starvation

Brain: relies on glucose and ketone bodies
Skeletal muscle: relies on uptae ketone bodies and fatty acids, releases amino acids
Liver: uptaes fatty acids, synthesizes and releases glucose and keto bodies
Adipocytes: fatty acids released and used for energy



(1) raises blood glucose
(2) anabolic
(3) lipolytic
- stimulates growth primarily through the regulation of the growth promoting hormones IGFs


Physiologic targets for AMPK

(1) stimulate GLUT-4 (enhance glucose transport)
(2) stimulate skeletal muscle fatty acid oxidation, glucose uptake
(3) inhibit synthesis of TAGs, glycogen, protein, cholesterol, FAs, insulin
(anabolic processes require ATP)