DHN 311 PRACTICE EXAM 2025/2026 QUESTIONS WITH
SOLUTIONS RATED A+
✔✔is phosphoglucomutase reversible or irreversible - ✔✔reversible
✔✔what does UDP - glucose phosphorylase do - ✔✔synthesis of UDP - glucose
alpha-D-glucose is attached to UDP
✔✔What is UDP-glucose used for? - ✔✔it is the source of all the glucosyl residues that
are added to the growing glycogen molecule.
attaches to the position 4 of the glucose to grow the glycogen chain
✔✔what happens to the two lost P molecules - ✔✔the high energy bond in
pyrophosphate (PPi) is hydrolyzed to two inorganic phosphates (Pi) by the enzyme
pyrophosphatase
✔✔what does glycogen synthase do - ✔✔forms alpha-1,4 glycosidic bonds.
integrating UDP - glucose into glycogen
✔✔glycogen fragment - ✔✔serves as a primer
✔✔glycogen primer - ✔✔glycogenin (substrate)
a protein that can serve as an acceptor of the glucose residues from UDP - glucose.
the hydroxyl group of the glycogenin (acceptor and enzyme) serves as the site at which
the initial glucoysyl unit is attached.
✔✔describe the elongation of glycogen chains by glycogen synthase - ✔✔elongation of
a glycogen chain/primer involves the transfer of glucose from UDP - glucose to the non-
reducing end of the growing chain, forming new glycosidic bonds between the hydroxyl
of carbon 1 of the activated glucose to carbon 4 of the accepting glucosyl residue
✔✔where are branches formed in glycogen - ✔✔approximately every 8-10 glucosyl
residues (glucose)
✔✔what does glycogen-branching enzyme do (glucosyl 4-6 transferase) - ✔✔catalyzes
the reaction (branching) to form alpha 1-6 linkage.
the enzyme removes a chain of 6 to 8 glucosyl residues from the non-reducing end of
the glycogen chain and attaches it to a non-terminal glucosyl residue by an alpha 1-6
linkage, creating a branch
, ✔✔Glycogenolysis - ✔✔degradation of glycogen
not the reversal of glycogenesis
✔✔where does glycogenolysis occur and does it require energy - ✔✔cytosol
no energy required
✔✔enzymes involved in glycogenolysis - ✔✔1. glycogen phosphorylase
2. glycogen debranching enzyme
3. phosphoglcomutase
✔✔what enzyme is shared by glycogenolysis and glycogenesis? -
✔✔phosphoglucomutase
✔✔what are the products of glycogen breakdown - ✔✔Glucose 1-P (90%)
free glucose (10%)
✔✔what does glycogen phosphorylase do - ✔✔breaks alpha-1,4 glycosidic bonds at the
non-reducing end to produce Glucose 1-P
✔✔How does glycogen phosphorylase work? - ✔✔phosphorylysis of the alpha,1-4
linkage using a P to break the bond
✔✔what does the de-branching enzyme do - ✔✔remove the last 4 glycosyl residues
attached at the branch after glucose 1-P is removed.
this is done through two different enzyme reactions
✔✔de-branching enzyme transferase reaction - ✔✔transfers the residues to the non-
reducing end of another chain, lengthening it
alpha 1-4 bonds are broken and made
✔✔de-branching enzyme hydrolysis reaction - ✔✔break the alpha 1-6 bond to release
free glucose
✔✔what does phosphoglucomutate do in glucogenolysis - ✔✔convert Glucose 1-P to
Glucose 6-P in the cytosol
✔✔what does phosphoglucomutate do in the liver - ✔✔the Glucose 6-P is
dephosphorylated to glucose and is released into the blood stream to maintain blood
glucose levels until the gluconeogenic pathway is actively producing glucose
SOLUTIONS RATED A+
✔✔is phosphoglucomutase reversible or irreversible - ✔✔reversible
✔✔what does UDP - glucose phosphorylase do - ✔✔synthesis of UDP - glucose
alpha-D-glucose is attached to UDP
✔✔What is UDP-glucose used for? - ✔✔it is the source of all the glucosyl residues that
are added to the growing glycogen molecule.
attaches to the position 4 of the glucose to grow the glycogen chain
✔✔what happens to the two lost P molecules - ✔✔the high energy bond in
pyrophosphate (PPi) is hydrolyzed to two inorganic phosphates (Pi) by the enzyme
pyrophosphatase
✔✔what does glycogen synthase do - ✔✔forms alpha-1,4 glycosidic bonds.
integrating UDP - glucose into glycogen
✔✔glycogen fragment - ✔✔serves as a primer
✔✔glycogen primer - ✔✔glycogenin (substrate)
a protein that can serve as an acceptor of the glucose residues from UDP - glucose.
the hydroxyl group of the glycogenin (acceptor and enzyme) serves as the site at which
the initial glucoysyl unit is attached.
✔✔describe the elongation of glycogen chains by glycogen synthase - ✔✔elongation of
a glycogen chain/primer involves the transfer of glucose from UDP - glucose to the non-
reducing end of the growing chain, forming new glycosidic bonds between the hydroxyl
of carbon 1 of the activated glucose to carbon 4 of the accepting glucosyl residue
✔✔where are branches formed in glycogen - ✔✔approximately every 8-10 glucosyl
residues (glucose)
✔✔what does glycogen-branching enzyme do (glucosyl 4-6 transferase) - ✔✔catalyzes
the reaction (branching) to form alpha 1-6 linkage.
the enzyme removes a chain of 6 to 8 glucosyl residues from the non-reducing end of
the glycogen chain and attaches it to a non-terminal glucosyl residue by an alpha 1-6
linkage, creating a branch
, ✔✔Glycogenolysis - ✔✔degradation of glycogen
not the reversal of glycogenesis
✔✔where does glycogenolysis occur and does it require energy - ✔✔cytosol
no energy required
✔✔enzymes involved in glycogenolysis - ✔✔1. glycogen phosphorylase
2. glycogen debranching enzyme
3. phosphoglcomutase
✔✔what enzyme is shared by glycogenolysis and glycogenesis? -
✔✔phosphoglucomutase
✔✔what are the products of glycogen breakdown - ✔✔Glucose 1-P (90%)
free glucose (10%)
✔✔what does glycogen phosphorylase do - ✔✔breaks alpha-1,4 glycosidic bonds at the
non-reducing end to produce Glucose 1-P
✔✔How does glycogen phosphorylase work? - ✔✔phosphorylysis of the alpha,1-4
linkage using a P to break the bond
✔✔what does the de-branching enzyme do - ✔✔remove the last 4 glycosyl residues
attached at the branch after glucose 1-P is removed.
this is done through two different enzyme reactions
✔✔de-branching enzyme transferase reaction - ✔✔transfers the residues to the non-
reducing end of another chain, lengthening it
alpha 1-4 bonds are broken and made
✔✔de-branching enzyme hydrolysis reaction - ✔✔break the alpha 1-6 bond to release
free glucose
✔✔what does phosphoglucomutate do in glucogenolysis - ✔✔convert Glucose 1-P to
Glucose 6-P in the cytosol
✔✔what does phosphoglucomutate do in the liver - ✔✔the Glucose 6-P is
dephosphorylated to glucose and is released into the blood stream to maintain blood
glucose levels until the gluconeogenic pathway is actively producing glucose
