Term
| why not store excess glucose as fat instead of glycogen? |
|
Definition
fat cannot be mobilized very rapidly
it cant be used as a source of energy i the absence of oxygen.
fat cant maintain glucose levels needed to feed the brain. |
|
|
Term
| why not store glucose as free glucose? |
|
Definition
takes too much energy to push into a cell.
cause water gradient to flow into cell causing lysis |
|
|
Term
| what makes glycogen more water soluble? |
|
Definition
|
|
Term
| what enzyme initiates glycogen breakdown? |
|
Definition
|
|
Term
| what is the name of two enzymes of the debranched glucose? |
|
Definition
| 4 alpha glucanotransferase and amylo alpha 1,6 glucosidase |
|
|
Term
| what is the function of 4 alpha glucanotransferase? |
|
Definition
| removes a strand of three glucosyl residues from a four-glucosyl residue branch of the glycogen molecule |
|
|
Term
| what is the function of amylo-alpha glucosidase? |
|
Definition
| hydrolyzes the alpha 1-6 linkage of the single glucosyl residue |
|
|
Term
| what is glycogen phosphorylase specific for? |
|
Definition
| a-1,4 glycosidic linkages |
|
|
Term
| on what end does glycogen phosphorylase act on |
|
Definition
| non reducing end of glycogen until 4 residues away from a,1-6 |
|
|
Term
| what allows the enzyme phosphorylation to continue degradation of glycogen |
|
Definition
|
|
Term
| what inactivates glycogen phosphorylase |
|
Definition
|
|
Term
| explain the regulation of glycogen phosphorylase |
|
Definition
phosphorylase kinase phosphorylates glycogen phosphorylase to the a form
phosphoprotein phosphatase dephosphorylates glycogen phosphorylase to the inactive form |
|
|
Term
| what is the effect of glucagon and epinephrine on glycogen phosphorylase? |
|
Definition
| activation of glycogen phosphorylase |
|
|
Term
| what is the effect of insulin on glycogen phosphorylase |
|
Definition
|
|
Term
| what effect does PKA play on phosphorylase activity? |
|
Definition
| it activates it to its active form |
|
|
Term
| what happens to PKA when cAMP is increased |
|
Definition
|
|
Term
| what is the function of the calmodulin complex on the phosphorylase kinase? |
|
Definition
| it activates both the a and b forms of phosphorylase kinase |
|
|
Term
| what are the effects of AMP on phosphorylase b? |
|
Definition
|
|
Term
| what is the function of glucose and ATP on phosphorylase a? |
|
Definition
|
|
Term
| what is the fate of degraded glycogen in liver? |
|
Definition
| G6P is cleaved by glucose 6 phosphatase to glucose to be released into the circulation |
|
|
Term
| what is the fate of glycogen in the peripheral tissues? |
|
Definition
| G6P will undergo glycolysis |
|
|
Term
| what is the fate of glycogen in white muscle? |
|
Definition
|
|
Term
| what is the fate of glycogen in red muscle |
|
Definition
| pyruvate, acetyl coA, and ultimately CO2 |
|
|
Term
| where is teh enzyme glucose 6 phosphatase located? |
|
Definition
|
|
Term
| how is glucose released into the blood? |
|
Definition
| a bidirectional facilitated glucose transporter (glut 1) at the plasma membrane |
|
|
Term
| what is the name of the activated glucose from which glycogen can be synthesized? |
|
Definition
|
|
Term
| what makes UDP-glucose energetically favorable? |
|
Definition
| hydrolysis of inorganic pyrophosphate by pyrophosphatase |
|
|
Term
| what is the immediate donor of glucose residues to be added at the non reducing end of glycogen |
|
Definition
|
|
Term
| what places glucose at the non reducing end of glycogen |
|
Definition
|
|
Term
| this provides a primer for glycogen synthesis by glycogen synthase |
|
Definition
|
|
Term
| what effect does phosphorylation have on glycogen phosphorylase and glycogen synthase? |
|
Definition
activates glycogen phosphorylase
inhibits glycogen synthase |
|
|
Term
| what form is glycogen synthase in when dephosphorylation occurs |
|
Definition
|
|
Term
| when are liver glycogen levels high? |
|
Definition
|
|
Term
| how long does stored glycogen last? |
|
Definition
|
|
Term
| what does muscle do with free glucose? |
|
Definition
|
|
Term
| is muscle glycogen important for maintenance of blood glucose in the post-absorbtive state |
|
Definition
|
|
Term
| is muscle glycogen important for maintenance of blood glucose in the post-absorbtive state |
|
Definition
|
|
Term
| what is the relationship between phoshphorylase a, glycogen synthase, and phosphoprotein phosphatase |
|
Definition
| phoshporylase a inhibits dephosphorylation of glycogen synthase b by phosphoprotein phosphatase |
|
|
Term
|
Definition
|
|
Term
| what is the relationship b/t phosphorylase and phosphoprotein phosphatase |
|
Definition
| phosphoprotein converts the phosphorylase to the inactive b form |
|
|
Term
| what is the relationship between phosphoprotein phosphatase and glycogen synthase |
|
Definition
| the active form of phosphoprotein phosphatase activates glycogen synthase |
|
|
Term
| what is the relationship between phosphoprotein phosphatase and glycogen synthase |
|
Definition
| the active form of phosphoprotein phosphatase activates glycogen synthase |
|
|
Term
| what is the relationship between glucagon and epinephrine in reference to glycogenolysis? |
|
Definition
| It stimulates it by increasing intracellular cAMP |
|
|
Term
| describe the signaling process of increased cAMP. |
|
Definition
activates PKA
PKA activates phosphorylase kinase
Phosphorylase kinase phosphorylates and activates glycogen phosphorylase
phosphorylase kinase phosphorylates and inhibits glycogen synthase |
|
|
Term
| when epinephrine binds in the liver, what is the effect? |
|
Definition
| stimulation of glycogenolysis by generation of inositol 1,4,5 triphosphate and diaglycerol |
|
|
Term
| how does increased cytosolic Ca effect signaling? |
|
Definition
| this activates phosphorylase kinase which activates glycogen phosphorylase with glycogenolysis. |
|
|
Term
| how does epinephrine affect signaling in the heart and skeletal muscle? |
|
Definition
| cAMP-->PKA-->phos. of phosphorylase kinase-->which phos. and activates glycogen phosphorylase. |
|
|
Term
| what activates muscle contraction? |
|
Definition
| intracellular Ca is increased and that activates phosphorylase kinase and glycogen phosphorylase |
|
|
Term
| what kind of transporter does hepatocytes have? |
|
Definition
|
|
Term
| what does glut2 transporter allow? |
|
Definition
| uptake of glucose to be dependent on the glucose concentration in the blood. |
|
|
Term
| how does insulin stimulate glycogen synthesis |
|
Definition
| activating phosphoprotein phosphotase which in turn dephosphorylates glycogen synthase. |
|
|
Term
| what does insulin induce in the muscle on its membrane?> |
|
Definition
| glut4 transporter-->glycogenesis |
|
|
Term
| what are the three types of liver glycogen storage diseases? |
|
Definition
| von gierke's disease, limit dextrinosis, amylopectinosis |
|
|
Term
| what is the enzyme deficiency in Von Gierke's disease? |
|
Definition
|
|
Term
| what is the enzyme deficiency in limit dextrinosis? |
|
Definition
|
|
Term
| what is the enzyme deficiency in amylopectinosis? |
|
Definition
|
|
Term
| what are some laboratory findings of Von Gierke |
|
Definition
administration of glucagon or epinephrine increases blood lactate with little or no rise in blood glucose
hyperlipidemia, hyperuricemia. |
|
|
Term
| what are the name of the glycogen storage diseases that affect the muscle? |
|
Definition
| McArdle's syndrome and Pompe's disease |
|
|
Term
| what is the enzyme deficiency in McArdle's syndrome |
|
Definition
|
|
Term
| what are some clinical manifestations of McArdle's syndrome |
|
Definition
| exercise intolerance, intense myoglobinuria |
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