LEC Glycogenolysis + Glycogenesis + Gluconeogenesis

Question 1

In glycogenolysis, ___ is cleaved by ___ to give ___

Answer 1

Glycogen; phosphate; a-D-glucose-1-phosphate

Question 2

T/F: in glycogenolysis, the cleavage reaction is phosphorlysis and not hydrolysis

Answer 2

T

Question 3

T/F: in glycogenolysis, ATP is required

Answer 3

F (no ATP is involved)

Question 4

Glycogenolysis is catalyzed by ___

Answer 4

Glycogen phosphorylase

Question 5

In the second reaction in glycogenolysis, ____ is ____ to _____

Answer 5

Glucose-1-phosphate; isomerized; glucose-6-phosphate

Question 6

In glycogenolysis, the isomerization from glucose-1-phosphate to glucose-6-phosphate is catalyzed by ____

Answer 6

Phosphoglucomutase

Question 7

The complete breakdown in the isomerization from glucose-1-phosphate to glucose-6-phosphate requires ____ to degrade the a1>6 linkages

Answer 7

Debranching enzymes

Question 8

T/F: glycogenesis is the exact reversal of glycogen breakdown to glucose

Answer 8

F

Question 9

Glycogen synthesis requires ___

Answer 9

Energy

Question 10

In glycogenesis, energy is supplied by ____

Answer 10

Hydrolysis of UTP

Question 11

In glycogenesis, ____ reacts with UTP to make _____

Answer 11

Glucose-1-phosphate; UDPG

Question 12

____ is added to a growing chain of glycogen, catalyzed by ____

Answer 12

UDPG; glycogen synthase

Question 13

In glycogenesis, the coupling of UDPG formation with ____ of ____ forms UDPG to ____

Answer 13

Hydrolysis; pyrophosphate; completion

Question 14

A major control point in the synthesis and breakdown of glycogen

Answer 14

Glycogen phosphorylase

Question 15

T/F: glycogen phosphorylase activity cannot be allosterically controlled; however, it can be controlled through covalent modification

Answer 15

T; F

Question 16

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

Answer 16

T; F

Question 17

What stimulates phosphorylation?

Answer 17

Hormonal signals (glucagon or epinephrine)

Question 18

After phorphorylation, glycogen synthase becomes ___ at the same time the hormonal signal is _____

Answer 18

Inactive; activating phosphorylase

Question 19

T/F: glycogen synthase cannot be phosphorylated by several other enzymes

Answer 19

F

Question 20

What enzyme phosphorylates glycogen synthase?

Answer 20

Phosphorylase kinase

Question 21

Dephosphorylation is by _____

Answer 21

Phosphoprotein phosphatase

Question 22

The storage form of glucose in animals and humans

Answer 22

Glycogen

Question 23

Glycogen releases ___ when energy demands are high

Answer 23

Glucose

Question 24

Glucose polymerizes to form _____ when the organism has no immediate need for the energy derived from glucose breakdown

Answer 24

Glycogen

Question 25

Control mechanisms in glycogen metabolism

Answer 25

Covalent modification and allosteric effects

Question 26

The conversion of pyruvate to glucose

Answer 26

Gluconeogenesis

Question 27

T/F: gluconeogenesis is the exact reversal of glycolysis

Answer 27

F

Question 28

Three irreversible steps in glycolysis

Answer 28

1. Phosphoenolpyruvate to pyruvate +ATP
2. Fructose-6-phosphate to fructose-1,6-biphosphate
3. Glucose to glucose-6-phosphate

Question 29

In the first step of gluconeogenesis, ____ is ____ to ____

Answer 29

Pyruvate; carboxylated; oxaloacetate

Question 30

CO2 carrier in gluconeogenesis

Answer 30

Biotin

Question 31

Pyruvate carboxylase is activated by ____

Answer 31

acetyl-CoA

Question 32

In the second step of gluconeogenesis, ____ of ___ is coupled with ____ to give ____

Answer 32

Decarboxylation; oxaloacetate; phosphorylation by GTP; PEP