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WEEK 9:
Carbohydrates 1: Glucose uptake and storage
| Question | Answer |
|---|---|
| metabolic pathways? | branched or interconnected enzymatic reactions (catabolic or anabolic) producing specific products |
| metabolites | substrates, intermediates and products |
| where do metabolic reactions take place | reactions can be compartmentalised (in eukaryotes) |
| transport systems | move metabolites between organelles, acting as control points |
| catabolic | breaks down |
| anabolic | builds |
| normal range for blood glucose | 4-8mM |
| glucose enantiomers | D and L |
| glucose anomers | alpha and beta |
| in solution, what form is glucose in equilibrium with | 6 membered ring (glucopyranose) |
| why does glucose form alpha and beta anomers in solution | C1 is asymmetric |
| furanose | 5 membered ring |
| how many monosaccharides do oligosaccharides have | 3-10 |
| where does final digestion occur | mucosal cells |
| ATP dependent Na+ co-transporter | glucose coupled to sodium, goes against concentration gradient and found in intestinal epithelial cells |
| Na+ independent (passive) transport | glucose moves down concentration gradient |
| disruption of glycogen metabolism can cause what | glycogen storage diseases (GSDs) |
| role of glycogen in muscles | main fuel reserve for ATP synthesis |
| amount of glycogen in muscles | 400g (1-2% fresh weight) |
| role of glycogen in liver | mobilisation of glycogen helps maintain blood glucose levels (5mM) |
| amount of glycogen in liver | 100g (10% fresh weight) |
| what creates chains in glycogen | alpha (1-4) glycosidic bonds |
| what creates branch points in glycogen | alpha (1-6) glycosidic bonds |
| glucose-1-phosphate (G1P) | initial substrate and product for glycogenesis/glycolysis |
| what is G1P formed from | glucose-6-phosphate using phosphoglucomutase |
| limit dextrin | enzymes making and breaking down glycogen need a minimum of 4 glucose residues to bind |
| glycogenin | enzyme needed as a primer to form initial 8-glucose chain |
| what is UDP-glucose formed from | glucose-1-phosphate and UTP |
| how are glycogen chains extended | via glycogen synthase using UDP-glucose to form alpha 1-4 linkages |
| how are glycogen branches extended | by adding transferase to break the chain and reattach those parts upstream as alpha 1-6 linkages |
| glycogen phosphorylase | enzyme which breaks down glycogen into glucose-1-phosphate |
| role of glycogen phosphorylase in glycogenolysis | cleaves alpha 1-4 bond of terminal glucose from glycogen and adds Pi to release glucose-1-phosphate until only 4 glucose units remain on branch |
| reaction for glycogenolysis | (Glucose)n + Pi → (Glucose)n-1 + glucose-1-phosphate |
| glycogen de-branching enzyme for glycogenolysis | has two active sites (transferase and glycosidase) |
| transferase active site in glycogenolysis | 3 of the 4 remaining units on the branch are moved to the end of the main chain |
| glycosidase active site in glycogenolysis | removes single remaining sugar on the branch via hydrolysis of the alpha 1-6 bond |
| order of enzymes in glycogenolysis | glycogen phosphorylase, transferase, glycosidase |
| describe glycogenolysis/glycogenesis in the liver | synthesis increases in well-fed state and breakdown increases during fasting |
| describe glycogenolysis/glucogenesis in muscles | synthesis increases in rest period and breakdown increases during exercise |
Created by:
kablooey
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