Sugar Metabolism Regulation

Question 1

How is a futile cycle created?

Answer 1

Anabolic and catabolic pathways occurring at the same time and place create a futile cycle.

Question 2

What do futile cycles generate?

Answer 2

Futile cycles generate heat, but that is the only product they make.

Question 3

What is a reciprocal regulator?

Answer 3

If the same molecule has opposite effects on catabolic and anabolic pathways, the molecule is a reciprocal regulator of the pathways. Reciprocal regulation of catabolic and anabolic pathways is a very efficient means of control.

Question 4

What is F1,6BPase also called?

Answer 4

F1,6BPase (also called FBPase or FBPase1)

Question 5

How does allosteric regulation by fructose-2,6-bisphosphate (F2,6BP) work on F1,6BPase?

Answer 5

The most important one is the allosteric regulation by fructose-2,6-bisphosphate (F2,6BP). F2,6BP activates PFK and inhibits F1,6BPase.It is the most sensitive allosteric regulator.

Question 6

PFK is also regulated by AMP (__), ATP (__).

Answer 6

PFK is also regulated by AMP (on), ATP (off).

Question 7

F1,6BPase is also regulated by c__e (__) and A_P (_).

Answer 7

F1,6BPase is also regulated by citrate (on) and AMP (off).

Question 8

The high energy indicator, ATP, turns off __ and turns on ___. The low energy indicator, AMP, has the opposite effect. Citrate is also an indicator of __ energy.

Answer 8

The high energy indicator, ATP, turns off PFK and turns on F1,6BPase. The low energy indicator, AMP, has the opposite effect. Citrate is also an indicator of high energy.

Question 9

Pyruvate kinase is activated by?

Answer 9

Pyruvate kinase is activated by feedforward activation by F1,6BP.

Question 10

Pyruvate kinase is inhibited by?

Answer 10

Pyruvate kinase is inibited by ATP and alanine (a product easily made from pyruvate).

Question 11

Pyruvate kinase is also controlled by covalent modification. ____ of the enzyme makes it __ active, whereas __ make it __ active.

Answer 11

Pyruvate kinase is also controlled by covalent modification. Phosphorylation of the enzyme makes it less active, whereas dephosphorylation make it more active.

Question 12

What is Pyruvate carboxylase inhibited by and activated by?

Answer 12

Pyruvate carboxylase is inhibited by ADP (low energy indicator) and activated by acetyl-CoA (high energy indicator)

Question 13

How is PEPCK regulated?

Answer 13

PEPCK is mostly regulated by whether or not the enzyme is synthesized, but ADP (low energy indicator) can inhibit the enzyme.

Question 14

F2,6BP is made and degraded by two different portions of the same protein, what are they?

Answer 14

PFK2 to refers to the kinase portion and FBPase -2 refers to the phosphatase portion

Question 15

The portion of the PFK2 catalyzing the synthesis of F2,6BP from F6P is __

Answer 15

The portion of the PFK2 catalyzing the synthesis of F2,6BP from F6P is PFK2.

Question 16

The portion of the protein catalyzing the breakdown of F2,6BP to F6P is __

Answer 16

The portion of the protein catalyzing the breakdown of F2,6BP to F6P is FBPase-2.

Question 17

F2,6BP is made and degraded by two different portions of the same protein, how are they regulated?

Answer 17

The two activities are regulated by phosphorylation of the protein by protein kinase A.

Question 18

When phosphorylated, what state are the PFK2 and FBPase in? activated or inactivated?

Answer 18

When phosphorylated, the PFK2 part of the enzyme is inactive and the FBPase-2 is active.

Question 19

When the phosphate is removed, what state are the PFK2 and FBPase in? activated or inactivated?

Answer 19

When the phosphate is removed from the protein by phosphoprotein phosphatase, the PFK2 becomes active and the FBPase-2 becomes inactive.

Question 20

Phosphorylation of the PFK2/FBPase-2 enzyme by protein kinase A is favored by?

Answer 20

Phosphorylation of the PFK2/FBPase-2 enzyme by protein kinase A is favored by 7TM signaling

Question 21

Dephosphorylation by phosphoprotein phosphatase is activated by?

Answer 21

Dephosphorylation by phosphoprotein phosphatase is activated by signaling by insulin.

Question 22

What does the phosphorylation of the PFK2/FBPase-2 enzyme favor?

Answer 22

Phosphorylation of the PFK2/FBPase-2 enzyme favors the breakdown of F2,6BP and the activation of gluconeogenesis and deactivation of glycolysis.

Question 23

What does the dephosphorylation of the PFK2/FBPase-2 enzyme favor?

Answer 23

Dephosphorylation of PFK2/FBPase-2 favors the synthesis of F2,6BP and the activation of glycolysis and the deactivation of gluconeogenesis. This is the heart of reciprocal regulation of these pathways.

Question 24

Regulation of glycolysis and gluconeogenesis mostly occurs by?

Answer 24

Overall, regulation of glycolysis and gluconeogenesis (besides the mechanisms noted above) occurs mostly allosterically using molecules that are indicative of the energy state of the cell.

Question 25

What do molecules indicating high cellular energy favor and inhibit?

Answer 25

Molecules indicating high cellular energy (like ATP) favor gluconeogenesis and inhibit glycolysis.

Question 26

What do molecules indicating low energy favor and inhibit?

Answer 26

Low energy molecules (like ADP or AMP) favor glycolysis and inhibit gluconeogenesis.

Question 27

What does the the Cori Cycle supply?

Answer 27

The Cori Cycle is a cycle of the body where the liver supplies glucose to muscles when needed.

Question 28

How does the Cory Cycle occur?

Answer 28

This occurs, for example, during heavy exercise when muscles are using oxygen faster than it can be delivered. When this happens, muscles start to make lactate and export it into the blood stream. Lactate travels to the liver where it is converted to pyruvate and then to glucose. The glucose is exported to the blood and is taken up the by muscles.