Question 1

Which of the following is an example of flux regulation,not flux control upon an increase in blood glucose levels?

Accepted Answer

A) Induction of insulin 
B) Increased glucose transport into cells 
C) Induction of the synthesis of hexokinase 
D) Induction of the synthesis of phosphofructokinase-1 
E) Activation of glycogen synthase

Question 2

There is reciprocal regulation of glycolytic and gluconeogenic reactions interconverting fructose-6-phosphate and fructose-1,6-bisphosphate.Which one of the following statements about this regulation is not correct?

Accepted Answer

A) Fructose-2,6-bisphosphate activates phosphofructokinase-1. 
B) Fructose-2,6-bisphosphate inhibits fructose-1,6-bisphosphatase. 
C) The fructose-1,6-bisphosphatase reaction is exergonic. 
D) The phosphofructokinase-1 reaction is endergonic. 
E) This regulation allows control of the direction of net metabolite flow through the pathway.

Question 3

Why is citrate,in addition to being a metabolic intermediate in aerobic oxidation of fuels,an important control molecule for a variety of enzymes?

Accepted Answer

The answer of Why is citrate,in addition to being a...

Question 4

Glycogen is converted to monosaccharide units by:

Accepted Answer

A) glucokinase. 
B) glucose-6-phosphatase 
C) glycogen phosphorylase. 
D) glycogen synthase. 
E) glycogenase.

Question 5

Diagram the pathway from glucose to glycogen;show the participation of cofactors and name the enzymes involved.

Accepted Answer

The answer of Diagram the pathway from glucose to glycogen;show...

Question 6

Explain the role of glycogenin.

Accepted Answer

The answer of Explain the role of glycogenin....

Question 7

Which of the following is not involved in up-regulating the transcription of glycolytic or gluconeogenic enzymes?

Accepted Answer

A) Phosphofructokinase-2 
B) Carbohydrate response element binding protein 
C) Sterol response element binding protein 
D) cAMP response element binding protein 
E) FOXO1

Question 8

Explain why reactions that are far from equilibrium need to be regulated.

Accepted Answer

The answer of Explain why reactions that are far from...

Question 9

Which one of the following is not a characteristic of phosphoprotein phosphorylase-1 (PP1)?

Accepted Answer

A) PP1 can be phosphorylated by protein kinase A (PK
A) . 
B) PP1 can dephosphorylate glycogen phosphorylase,glycogen synthase,and phosphorylase kinase. 
C) PP1 is allosterically activated by glucose-6-phosphate. 
D) PP1 is inhibited by activated glycogen phosphorylase 
E) PP1 is phosphorylated by glycogen synthase kinase-3 (GSK3).

Question 10

Which of the following statements is true of muscle glycogen phosphorylase?

Accepted Answer

A) It catalyzes phosphorolysis of the ($\alpha$1 $\rightarrow$  6)bonds at the branch points of glycogen. 
B) It catalyzes the degradation of glycogen by hydrolysis of glycosidic bonds. 
C) It degrades glycogen to form glucose 6-phosphate. 
D) It exists in an active (a)form and an inactive (b)form that is allosterically regulated by AMP. 
E) It removes glucose residues from the reducing ends of the glycogen chains.

Question 11

Which one of the following statements about mammalian glycogen synthase is not correct?

Accepted Answer

A) It is especially predominant in liver and muscle. 
B) The donor molecule is a sugar nucleotide. 
C) The phosphorylated form of this enzyme is inactive. 
D) This enzyme adds glucose units to the nonreducing end of glycogen branches. 
E) This enzyme adds the initial glucose unit to a tyrosine residue in glycogenin.

Question 12

What is a "futile cycle"? Give an example of a potential futile cycle in carbohydrate metabolism,and describe methods used by cells or organisms to avoid the operation of the futile cycle.

Accepted Answer

The answer of What is a "futile cycle"? Give an...

Question 13

An increase in which of these compounds leads to the dephosphorylation and activation of phosphofructokinase-2?

Accepted Answer

A) Glucagon 
B) Xyulose-5-phosphate 
C) Pyruvate 
D) Citrate 
E) ADP

Question 14

Gluconeogenesis must use "bypass reactions" to circumvent three reactions in the glycolytic pathway that are highly exergonic and essentially irreversible.Reactions carried out by which three of the enzymes listed must be bypassed in the gluconeogenic pathway? 1)Hexokinase
2)Phosphoglycerate kinase
3)Phosphofructokinase-1
4)Pyruvate kinase
5)Triosephosphate isomerase

Accepted Answer

A) 1,2,3 
B) 1,2,4 
C) 1,4,5 
D) 1,3,4 
E) 2,3,4

Question 15

Aside from maintaining the integrity of its hereditary material,the most important general metabolic concern of a cell is:

Accepted Answer

A) keeping its glucose levels high. 
B) maintaining a constant supply and concentration of ATP. 
C) preserving its ability to carry out oxidative phosphorylation. 
D) protecting its enzymes from rapid degradation. 
E) running all its major metabolic pathways at maximum efficiency.

Question 16

Reaction steps that are far from equilibrium are good control points in metabolic pathways because

Accepted Answer

A) the net flux through those steps is easily reversed. 
B) the rate differences between the forward and reverse steps are often small. 
C) these reactions occur most frequently in the cell. 
D) these reactions are highly endergonic. 
E) these reactions are highly exergonic.

Question 17

Explain the difference between homeostasis and equilibrium.

Accepted Answer

The answer of Explain the difference between homeostasis and equilibrium....

Question 18

Describe the process of glycogen breakdown in muscle.Include a description of the structure of glycogen,the nature of the breakdown reaction and the breakdown product,and the required enzyme(s).

Accepted Answer

The answer of Describe the process of glycogen breakdown in...

Question 19

Briefly explain the differences between the flux control,elasticity,and response coefficients.

Accepted Answer

The answer of Briefly explain the differences between the flux...

Question 20

In mammalian liver,glucose-1-phosphate,the product of glycogen phosphorylase,can enter glycolysis or replenish blood glucose.Describe the reactions by which these two processes are carried out.

Accepted Answer

The answer of In mammalian liver,glucose-1-phosphate,the product of glycogen phosphorylase,can...

Exam 15: Principles of Metabolic Regulation