Glycogenesis, Glycogenolysis & Others 3-12

College Of Medicine (com) Indt 8148 Metabolism & Nutrition with Garrett/olson at University of Oklahoma Health Sciences Center

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By: Jenna Geohagan
Created: 2012-03-13
Size: 46 flashcards
Views: 15

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After an ingestion of a bolus of glucose, liver ______ stores become the primary source of blood glucose for up to 18 hours.

Glycogen!

Glycogen is a rapidly mobilizable source of _______ from the liver.

blood glucose. (Other tissues store glycogen, but it is used internally).

Glycogen is a ______ ______ polysaccharide, consisting of ______ attached at its reducing end to what?

branched chain: consisting of poly-alpha-D-glucose attached to glycogenin.

Initial synthesis of glycogen requires _______, an enzyme that autoglucosylates itself to form a primer.

Glycogenin

Glycogen is formed from _________ via intermediaries.

Glucose 6- Phosphate

_____ ____ hydrolyzes a ~5-mer from the non-reducing terminus and transfers it to a new glucose approximately 4 positions in from breakpoint to generate a branch point.

Branching enzyme

__________ elongates the prime (glycogenin) by addition of alpha1,4-linked glucose residues.

Glycogen synthase

Discuss Glycogen synthesis

Glucose 6-phosphate---(Phosphoglucomutase)---->glucose 1-phosphate---(UDP-glucose pyrophosphorylase)--> UDP-glucose---- (Glycogen synthase)---> adding more UDP-glucose----(Branching enzyme)----> glycogen!

In glycogenolysis, or the breakdown of glycogen, chain shortening is accomplished by?

glycogen phosphorylase. Adds a phosphate resulting in the formation of glucose 1-phosphate.

glycogenolysis

breaking down glycogen to glucose

Branch removal requires what 2 enzymes? What does each do?

Debranching enzymes:

4:4 transferase activity-- transfers the outer 3 of 4 residues to another branch

1:6 glucosidase activity: removes the single remaining glucose as free glucose

Glucose 1-phosphate is reversibly converted to glucose 6-phosphate by what?

phosphoglucomutase

In the liver, glucose 6-phosphate is transported into the ER by ________ and converted into glucose by __________.

Transported by: Glucose 6-phosphate translocase

Converted by: glucose 6-phosphatase

Describe Von Gierke disease (Glu 6-P def) and Glu 6-P Translocase Deficiency

Affect liver and kidney, severe fasting hypoglycemia, progressive renal disease, growth retardation and delayed puberty.

A deficiency in lysosomal acid maltase leads to vacuolar glycogen accumulation storage disease called?

Pompe Disease

Describle McArdle Syndrome

Skeletal Muscle Glycogen Phosphorylase or Myophosphorylase deficiency.

Weakness or cramping, no rise in blood lactate during exercise, normal mental devo, relatively benign condition.

Impaired branching enzyme leads to what glycogen storage disease?

Type IV: Andersen's

Hormonal regulation: Glucagon promotes __________, while insulin promotes __________.

Glucagon (fasting/starvation): glycogenolysis

Insulin: Glycogenesis

Glucagon binds its receptor which activates adenylyl cyclase resulting in accumulation of cAMP, which activates ____________, which in turn of phosphorylates ___________ and converts it to its active form. This phosphorylates _______ and converts it to its active form too! Leads to glycogen degradation.

Glucagon binds its receptor which activates adenylyl cyclase resulting in accumulation of cAMP, which activates cAMP dependent protein kinase, which in turn phosphorylates glycogen phosphorylase kinase and converts it to its active form. This phosphorylates glycogen phoshorylase and converts it to its active form too! Leads to glycogen degradation,

Insulin activates protein phosphate-1, which dephosphorylates and returns ______ and _____ to their less active b forms.

glycogen phosphorylase kinase and glycogen phosphorylase.

______ binds to calmodulin subunit of phosphorylase kinase and activates it without phosphorylation.

Calcium

Glycogenesis is inhibited by:

ATP and Glucose (inhibits glycogen phosphorylase a)

Glucagon-activated cAMP-dependent protein kinase A phosphorylates _______ converting it to its active form and allowing synthesis.

Glycogen synthase

Insulin activates glycogen synthase via dephosphorylation by activating _________

protein phosphatase-1

Glycogenesis is promoted by high energy levels, i.e. _____

Glucose 6-Phosphate

Glycogenolysis is promoted by:

low energy (AMP), epinephrine, or Calcium

During the fasting state, there is a decrease in blood glucose so a decrease in insulin release and an increase in glucagon release, which leads to increased protein kinase activity and _____________.

___ signals low energy and allosterically activates glycogen phosphorylase b in the absence of its phosphorylation.

AMP

During the fed state, ingestion of glucose leads to increased blood glucose, which leads to release of insulin and decreased release of glucagon, which leads to protein phosphatase activity and ________!

Fructose occurs primarily with glucose as the disaccharide?

sucrose

Galactose occurs primarily with glucose as?

lactose

Fructose and lactose do not promote secretion of insulin because they are

insulin independent

Cytoplasmic fructose is trapped mainly by fructokinase as __________.

Fructose 1-Phosphate.

How do you bypass traditional glycolytic control via phosphofructokinase-1? Cleave Fructose 1-Phosphate with ________ to create dihydroxyacetone and glyceraldehyde?

aldolase b

Recessive, absence of aldolase b, hypoglycemia, vomiting, jaundice, hepatomegaly, hepatic failure, and maybe death. Therapy= rapid detection & removal of fructose/sucrose from the diet.

Hereditary Fructose Intolerance. OrFructose Poisoning.

Utilization of fructose is greatest in the ____, but rxns also occur in the kidney.

LIVER

Lack of fructokinase, autosomal recessive, benign condition, and fructose accumulates in the liver.

Essential fructosuria

What is a source of fructose and a sperm nutrient?

Sorbitol

Excess sorbitol can occur under conditions of _________, which result in osmotic swelling, cataract formation, peripheral neuropathy, and microvascular swelling.

diabetes: high intracellular glucose

Mannose is trapped intracellularly by

hexokinase

Mannose 6-Phosphate can be isomerized by phosphomannose isomerase to?

Fructose 6-Phosphate

Cytoplasmic galactose is phosphorylated to galactose 1-phosphate by

galactokinase

In galactose metabolism, an exchange rxn catalyzed by ______ yields UDP-galactose and glucose 1-phosphate.

galactose 1-phosphate uridyltransferase

Recessive, elevation of galactose in blood and urine, and causes galactitol accumulation if galactose is present in the diet.

Galactokinase deficiency

Uridyltransferase deficiency, recessive, galactosemia, vomiting, diarrhea, jaundice, accumulation of galactose 1-phosphate and galactitol in nerves, lens, liver, etc. Liver damage, MR, and cataracts. Therapy: removal of galactose (lactose) from diet

classic galactosemia

About this deck

By: Jenna Geohagan
Created: 2012-03-13
Size: 46 flashcards
Views: 15

About StudyBlue

“Simply amazing. The flash cards are smooth, there are many different types of studying tools, and there is a great search engine. I praise you on the awesomeness.”
Dennis