LEC Glycogenolysis + Glycogenesis + Gluconeogenesis Flashcards
In glycogenolysis, ___ is cleaved by ___ to give ___
Glycogen; phosphate; a-D-glucose-1-phosphate
T/F: in glycogenolysis, the cleavage reaction is phosphorlysis and not hydrolysis
T
T/F: in glycogenolysis, ATP is required
F (no ATP is involved)
Glycogenolysis is catalyzed by ___
Glycogen phosphorylase
In the second reaction in glycogenolysis, ____ is ____ to _____
Glucose-1-phosphate; isomerized; glucose-6-phosphate
In glycogenolysis, the isomerization from glucose-1-phosphate to glucose-6-phosphate is catalyzed by ____
Phosphoglucomutase
The complete breakdown in the isomerization from glucose-1-phosphate to glucose-6-phosphate requires ____ to degrade the a1>6 linkages
Debranching enzymes
T/F: glycogenesis is the exact reversal of glycogen breakdown to glucose
F
Glycogen synthesis requires ___
Energy
In glycogenesis, energy is supplied by ____
Hydrolysis of UTP
In glycogenesis, ____ reacts with UTP to make _____
Glucose-1-phosphate; UDPG
____ is added to a growing chain of glycogen, catalyzed by ____
UDPG; glycogen synthase
In glycogenesis, the coupling of UDPG formation with ____ of ____ forms UDPG to ____
Hydrolysis; pyrophosphate; completion
A major control point in the synthesis and breakdown of glycogen
Glycogen phosphorylase
T/F: glycogen phosphorylase activity cannot be allosterically controlled; however, it can be controlled through covalent modification
T; F
T/F: the activity of glycogen synthase is subject to the same type of covalent modification as glycogen phosphorylase; the response is the same as well
T; F
What stimulates phosphorylation?
Hormonal signals (glucagon or epinephrine)
After phorphorylation, glycogen synthase becomes ___ at the same time the hormonal signal is _____
Inactive; activating phosphorylase
T/F: glycogen synthase cannot be phosphorylated by several other enzymes
F
What enzyme phosphorylates glycogen synthase?
Phosphorylase kinase
Dephosphorylation is by _____
Phosphoprotein phosphatase
The storage form of glucose in animals and humans
Glycogen
Glycogen releases ___ when energy demands are high
Glucose
Glucose polymerizes to form _____ when the organism has no immediate need for the energy derived from glucose breakdown
Glycogen
Control mechanisms in glycogen metabolism
Covalent modification and allosteric effects
The conversion of pyruvate to glucose
Gluconeogenesis
T/F: gluconeogenesis is the exact reversal of glycolysis
F
Three irreversible steps in glycolysis
- Phosphoenolpyruvate to pyruvate +ATP
- Fructose-6-phosphate to fructose-1,6-biphosphate
- Glucose to glucose-6-phosphate
In the first step of gluconeogenesis, ____ is ____ to ____
Pyruvate; carboxylated; oxaloacetate
CO2 carrier in gluconeogenesis
Biotin
Pyruvate carboxylase is activated by ____
acetyl-CoA
In the second step of gluconeogenesis, ____ of ___ is coupled with ____ to give ____
Decarboxylation; oxaloacetate; phosphorylation by GTP; PEP
