Glycogenolysis - wikipedia Glycogenolysis Not to be confused with Glycolysis, Glycogenesis, or Gluconeogenesis. Glycogen Glucose Glucose - 6 - phosphate Glycogenolysis is the breakdown of glycogen ( n ) to glucose - 6 - phosphate and glycogen ( n - 1 ). Glycogen branches are catabolized by the sequential removal of glucose monomers via phosphorolysis, by the enzyme glycogen phosphorylase. Contents 1 Mechanism 2 Function 3 Regulation 4 Clinical significance 5 Pathology 6 See also 7 References 8 External links Mechanism The overall reaction for the breakdown of glycogen to glucose - 1 - phosphate is : glycogen + P ⇌ glycogen + glucose - 1 - phosphate Here, glycogen phosphorylase cleaves the bond linking a terminal glucose residue to a glycogen branch by substitution of a phosphoryl group for the α ( 1 → 4 ) linkage. Glucose - 1 - phosphate is converted to glucose - 6 - phosphate by the enzyme phosphoglucomutase. Glucose residues are phosphorolysed from branches of glycogen until four residues before a glucose that is branched with a α ( 1 → 6 ) linkage. Glycogen debranching enzyme then transfers three of the remaining four glucose units to the end of another glycogen branch. This exposes the α ( 1 → 6 ) branching point, which is hydrolysed by α ( 1 → 6 ) glucosidase, removing the final glucose residue of the branch as a molecule of glucose and eliminating the branch. This is the only case in which a glycogen metabolite is not glucose - 1 - phosphate. The glucose is subsequently phosphorylated to glucose - 6 - phosphate by hexokinase. Function Glycogenolysis takes place in the cells of the muscle and liver tissues in response to hormonal and neural signals. In particular, glycogenolysis plays an important role in the fight - or - flight response and the regulation of glucose levels in the blood. In myocytes ( muscle cells ), glycogen degradation serves to provide an immediate source of glucose - 6 - phosphate for glycolysis, to provide energy for muscle contraction. In hepatocytes ( liver cells ), the main purpose of the breakdown of glycogen is for the release of glucose into the bloodstream for uptake by other cells. The phosphate group of glucose - 6 - phosphate is removed by the enzyme glucose - 6 - phosphatase, which is not present in myocytes, and the free glucose exits the cell via GLUT2 facilitated diffusion channels in the hepatocyte cell membrane. Regulation Glycogenolysis is regulated hormonally in response to blood sugar levels by glucagon and insulin, and stimulated by epinephrine during the fight - or - flight response. In myocytes, glycogen degradation may also be stimulated by neural signals. Clinical significance Parenteral ( intravenous ) administration of glucagon is a common human medical intervention in diabetic emergencies when sugar can not be given orally. It can also be administered intramuscularly. Pathology Mutations at the liver enzyme glycogen phosphorylase ( GPLL, 847 aa ) lead to glycogen storage disease VI ( Hers disease ). Mutations at the muscle enzyme glycogen phosphorylase ( GPMM, 842 aa ) lead to McArdle 's disease. Deficiencies at the glycogen debranching enzyme lead to glycogen storage disease III ( Oxford Dictionary of BioMedicine, 2010 ). See also Glycogenesis References Jump up ^ `` Glycogenesis ''. Jump up ^ Lodish ; et al. ( 2007 ). Molecular Cell Biology ( 6th ed. ). W.H. Freeman and Company. p. 658. ISBN 1429203145. External links The chemical logic of glycogen degradation at ufp.pt Glycogenolysis at the US National Library of Medicine Medical Subject Headings ( MeSH ) Metabolism, catabolism, anabolism General Metabolic pathway Metabolic network Primary nutritional groups Energy metabolism Aerobic respiration Glycolysis → Pyruvate decarboxylation → Citric acid cycle → Oxidative phosphorylation ( electron transport chain + ATP synthase ) Anaerobic respiration Electron acceptors are other than oxygen Fermentation Glycolysis → Substrate - level phosphorylation ABE Ethanol Lactic acid Specific paths Protein metabolism Protein synthesis Catabolism Carbohydrate metabolism ( carbohydrate catabolism and anabolism ) Human Glycolysis ⇄ Gluconeogenesis Glycogenolysis ⇄ Glycogenesis Pentose phosphate pathway Fructolysis Galactolysis Glycosylation N - linked O - linked Nonhuman Photosynthesis Anoxygenic photosynthesis Chemosynthesis Carbon fixation Xylose metabolism Radiotrophism Lipid metabolism ( lipolysis, lipogenesis ) Fatty acid metabolism Fatty acid degradation ( Beta oxidation ) Fatty acid synthesis Other Steroid metabolism Sphingolipid metabolism Eicosanoid metabolism Ketosis Reverse cholesterol transport Amino acid Amino acid synthesis Urea cycle Nucleotide metabolism Purine metabolism Nucleotide salvage Pyrimidine metabolism Other Metal metabolism Iron metabolism Ethanol metabolism Metabolism map Carbon Fixation Photo - respiration Pentose Phosphate Pathway Citric Acid Cycle Glyoxylate Cycle Urea Cycle Fatty Acid Synthesis Fatty Acid Elongation Beta Oxidation Peroxisomal Beta Oxidation Glyco - genolysis Glyco - genesis Glyco - lysis Gluconeo - genesis Decarb - oxylation Fermentation Keto - lysis Keto - genesis feeders to Gluconeo - genesis Direct / C4 / CAM Carbon Intake Light Reaction Oxidative Phosphorylation Amino Acid Deamination Citrate Shuttle Lipogenesis Lipolysis Steroidogenesis MVA Pathway MEP Pathway Shikimate Pathway Transcription & Replication Translation Proteolysis Glycosy - lation Sugar Acids Double / Multiple Sugars & Glycans Simple Sugars Inositol - P Amino Sugars & Sialic Acids Nucleotide Sugars Hexose - P Triose - P Glycerol P - glycerates Pentose - P Tetrose - P Propionyl - CoA Succinate Acetyl - CoA Pentose - P P - glycerates Glyoxylate Photosystems Pyruvate Lactate Acetyl - CoA Citrate Oxalo - acetate Malate Succinyl - CoA α - Keto - glutarate Ketone Bodies Respiratory Chain Serine Group Alanine Branched - chain Amino Acids Aspartate Group Homoserine Group & Lysine Glutamate Group & Proline Arginine Creatine & Polyamines Ketogenic & Glucogenic Amino Acids Amino Acids Shikimate Aromatic Amino Acids & Histidine Ascorbate ( Vitamin C ) δ - ALA Bile Pigments Hemes Cobalamins ( Vitamin B ) Various Vitamin B 's Calciferols ( Vitamin D ) Retinoids ( Vitamin A ) Quinones ( Vitamin K ) & Carotenoids ( Vitamin E ) Cofactors Vitamins & Minerals Antioxidants PRPP Nucleotides Nucleic Acids Proteins Glycoproteins & Proteoglycans Chlorophylls MEP MVA Acetyl - CoA Polyketides Terpenoid Backbones Terpenoids & Carotenoids ( Vitamin A ) Cholesterol Bile Acids Glycero - phospholipids Glycerolipids Acyl - CoA Fatty Acids Glyco - sphingolipids Sphingolipids Waxes Polyunsaturated Fatty Acids Neurotransmitters & Thyroid Hormones Steroids Endo - cannabinoids Eicosanoids Major metabolic pathways in metro - style map. Click any text ( name of pathway or metabolites ) to link to the corresponding article. Single lines : pathways common to most lifeforms. Double lines : pathways not in humans ( occurs in e.g. plants, fungi, prokaryotes ). Orange nodes : carbohydrate metabolism. Violet nodes : photosynthesis. Red nodes : cellular respiration. Pink nodes : cell signaling. Blue nodes : amino acid metabolism. Grey nodes : vitamin and cofactor metabolism. Brown nodes : nucleotide and protein metabolism. Green nodes : lipid metabolism. Metabolism : carbohydrate metabolism, glycogenesis and glycogenolysis enzymes Glycogenesis Phosphoglucomutase UDP - glucose pyrophosphorylase Glycogen synthase Glycogen branching enzyme Glycogenin Glycogenolysis extralysosomal : Glycogen phosphorylase Debranching enzyme Phosphoglucomutase lysosomal : Alpha - glucosidase ( Acid ) Regulation Phosphorylase kinase Protein phosphatase Retrieved from `` https://en.wikipedia.org/w/index.php?title=Glycogenolysis&oldid=799064699 '' Categories : Metabolic pathways Hepatology Diabetes Talk Contents About Wikipedia Bosanski Català Čeština Dansk Deutsch Español فارسی Français Galego Bahasa Indonesia Italiano עברית Қазақша Latina Bahasa Melayu Nederlands 日本 語 Occitan Polski Português Русский Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska தமிழ் Українська 中文 Edit links This page was last edited on 5 September 2017, at 12 : 17. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. 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Question: where does glycogenolysis take place in the cell
Answer: in the cells of the muscle and liver tissues