Regulation of carbohydrate metabolism

Question 1

What is gluconeogenesis

Answer 1

The synthesis of glucose from non-carbohydrate precursors.

Question 2

What is required for gluconeogenesis to occur

Answer 2

A source of energy and a source of carbon is required.

Question 3

Outline the gluconeogenic pathway

Answer 3

OAA—>glucose formed (using 6 ATP per molecule of glucose formed) —>glucose

Question 4

How does H+ concentration affect PFK-1 activity

Answer 4

H+ inhibits PFK-1 to stop glycolysis as the lactic acid produced leads to cellular damage, however, this can be overcome by high AMP resulting in chest pains experienced in heart attacks and angina.

Question 5

What are some allosteric regulators of PFK-1

Answer 5

F6P (activates), F2,6P (activates, most potent activator as it indicates high rates of glucose entry), citrate (inhibits as it indicates TCA cycle overload so glycolysis needs to stop)

Question 6

What is the actions of F-1,6, BPase

Answer 6

It is a gluconeogenic enzyme which catalyses F1,6,BP back into F6P.

Question 7

What is F-2,6-BP

Answer 7

It is generated from F6P via PFK2- and degraded by F-2,6, BPase.
It increases the rate of glycolysis and is decreased by high levels of citrate

Question 8

Why does the liver require extra control

Answer 8

The liver produces glucose to maintain blood glucose levels so glycolysis must be inhibited meanwhile gluconeogenesis is activated. PFK-1 AND F-1,6-BPase are controlled by levels of F-2,6-BP Which is affected by hormones.

Question 9

How is F-2,6-BPase and PFK-2 activated and how is this achieved

Answer 9

When it is phosphorylated and when it is not phosphorylated. Glucagon increases cAMP which increases cAMPPK and it can phosphorylate F-2,6-BPase to activate it and PFK-2 to deactivate it which decreases the concentration of F-2,6-BP to decrease the rate of glycolysis and gluconeogenesis is favoured