Medicine Notes > Oxford Medicine Notes > Biochemistry Notes

Storage Of Glucose Notes

This is a sample of our (approximately) 8 page long Storage Of Glucose notes, which we sell as part of the Biochemistry Notes collection, a First package written at Oxford in 2014 that contains (approximately) 216 pages of notes across 33 different documents.

Learn more about our Biochemistry Notes

The original file is a 'Word (Docx)' whilst this sample is a 'PDF' representation of said file. This means that the formatting here may have errors. The original document you'll receive on purchase should have more polished formatting.

Storage Of Glucose Revision

The following is a plain text extract of the PDF sample above, taken from our Biochemistry Notes. This text version has had its formatting removed so pay attention to its contents alone rather than its presentation. The version you download will have its original formatting intact and so will be much prettier to look at.

Bavidra kulendrarajah Storage of glucose
-glucose can't be stored as high concentrations disrupt the osmotic balance of the cell- cell death/damage
-in animals storage form of glucose is glycogen- nonosmotically active polymer and can be readily be mobilised into glucose
-most of the glucose residues in glycogen are linked by a-1,4-glycosidic bonds. Branches at about every 10th residue are created by a-1,6-glycosidic bonds Glycogen: large, highly hydrated, branched polymer of glucose and occupies a large volume of the cell so storage is very limited Present in all tissues but significant amounts in liver and muscle- granules in the cytoplasm Reserves Liver: 70g 280Kcal - store helps to maintain constant blood glucose concentrations Muscle 225g 900Kcal -local source of glucose for concentration-glycogen is an endogenous substrate Blood glucose 15g 60kcal Total: 310grams

1240kcal (less than 5% of body energy stores)

Glycogen synthesis
-takes place when glucose is abundant Glucose-6-P  glucose-1-P  UDP-Glucose  glycogen and other complex sugars
-substrate: activated from of glucose uridine diphosphate glucose (UDPglucose) - glucose1-P reacts with Uridine triphosphate (UTP) to form UDP-glucose and PPi
-Glycogen synthase: catalyses the reaction where UDP-glucose is added to the C4 hydroxyl group of a terminal glucose residue to form an a-1,4 glycosidic bonds. The UDP group is displaced by the hydroxyl group. This forms a growing chain of glucose molecules. UDP-Glucose + (glycogen)n  (Glycogen)n+1 + UDP

Bavidra kulendrarajah
-Glycogen synthase can only add glucose residues to a polysaccharide chain that has more than 4 residues. Glycogen synthesis requires a primer. Glycogenin , is a protein, that acts as a primer that can autoglycosylation and forms the nucleus for glycogen synthesis and controls the size of the product.
-Glycogen synthase catalyses only the formation of alpha 1,4 linkages. Another enzyme forms alpha-1,6 linkages.
-branching: increases the solubility and increases the number of ends- the number of terminal residues increased which are the sites of action of glycogen phosphorylase and synthase, so increases the rate of glycogen synthesis/degradation Energetic cost of synthesis
-one ATP is consumed per residue of glucose added
-as ATP is needed to synthesise UTP from UDP ATP + UDP  UTP + ADP Glycogen mobilisation Phosphorolysis (cleavage of the bond by addition of orthophosphate): Glycogen phosphorylase cleaves the glycogen by adding an orthophosphate (Pi) to form glucose-1-phosphate (Glycogen)n + Pi  (Glycogen)n-1 + Glucose-1-P
-glycogen phosphorylase acts on the terminal ends of the glycogen as the ends have a free 0H group on C4. Orthophosphate splits the glycosidic linkaged between C1 of terminal residue and C4 of the adjacent one
-Glucose-1-P is converted into Glucose-6-P by isomerase enzyme, phosphoglucomutase
-There is sequential removal of glucose residues from free terminals until 4 th residue from a branch is reached. At this point the glycogen phosphorylase cannot remove residues
-Glycogen transferase shifts a block of three glucose residues from one outerbranch to another. This transfer results in a single glucose residue attached by an alpha-1,6-glycosidic linkages
-alpha-1,6-glucosidase (debranching enzyme) hydrolyses the alpha-1,6glycosidic bond. As phoshporolysis doesn't occur, a free glucose molecule is released and the phosphorylated by hexokinase.

****************************End Of Sample*****************************

Buy the full version of these notes or essay plans and more in our Biochemistry Notes.