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BMSC 230- Glycogen metabolism questions with correct answers 2024/2025
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BMSC 230- Glycogen metabolism questions with correct answers 2024/2025
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BMSC 230- Glycogen metabolismdescribe glycogens structure and function - ANSa highly branched homopolysaccharide of
glucose
it stores glucose when it is plentiful
where is glycogen located in the body - ANSin all tissues, but predominantly the liver, and
secondly muscles
explain what linkages are present in glycogen - ANSthe main chain is α(1→4), and α(1→6)
linkages are found at branch points
what is the reducing end of a sugar - ANSthe end with a free anomeric carbon
does glycogen synthase require NRG - ANSno; it is a synthase
what is special about the reducing end of a sugar - ANSit is the end where sugars are added or
removed
glycogen has 2000 nonreducing ends
what does this mean - ANS2000 glucose residues can be added or removed, simultaneously
what is glycogenin - ANSa small protein found in the middle of glycogen, that is needed to start
synthesis of a brand new glycogen from scratch
what enzyme is found in both g.n.g and glycogen breakdown - ANSglucose-6-phosphatase
what 2 pathways must you be careful not to confuse - ANSgluconeogenesis and glycogenesis
where in the body is glucose-6-phosphatase mainly found - ANSin the liver: since one of its
functions is to maintain constant blood glucose
if glycogen is being broken down in the muscle, what step would you expect to be skipped -
ANSthe conversion of G-6-P to glucose
instead, G-6-P will simply enter the glycolytic pathway
what does glycogenesis require to get started - ANSan activated precursor: many anabolic
pathways require this
, what can we tell from the name of a "phosphorylase" enzymes - ANSit catalyzes a
phosphoryolysis rxn: splitting by adding a phosphate
careful not to confuse with phosphatase
what residues will glycogen phosphorylase remove - ANSmain chain α(1→4) linkages, and
branched chain α(1→4) linkages, UP TO 4 branched residues remaining
what does the enzyme transferase do - ANStransfers 3 branched chain glucose residues on
glycogen to the main chain, leaving only the α(1→6) linked residue remaining
what 2 enzymes are involved in converting the product of glycogen phosphorylase into glucose -
ANSphosphoglucomutase forms G-6-P, and
glucose-6-phosphatase dephosphorylates it to make glucose + Pi
does glycogen synthesis or breakdown require an activated prescursor
what is the activated precursor - ANSsynthesis
UDP-Glucose
what enzyme is used both in glycogen synthesis and breakdown - ANSphosphoglucomutase
what is the "main" enzyme that actually synthesizes glycogen - ANSglycogen synthase
what is the difference between a synthase and synthatase enzyme - ANSsynthase doesn't
require NRG
synthatase requires NRG
what does glycogen synthase need help doing when synthesizing glycogen
what provides this help - ANSadding branch points
the branching enzyme does this by removing 7 glucose residues from the main chain and
adding them as a branch
how far apart must branches on glycogen be - ANSat least 4 residues
glycogen synthase can only be directly used to add glucoses to an existing glycogen molecule.
what if we want to start a new molecule from scratch? - ANSthe protein glycogenin is a dimer:
the 1st subunit will catalyze the addition of 7 glucoses onto Tyr 194 of the second unit.
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