Glycolysis and gluconeogenesis are tightly regulated, opposing metabolic pathways that help control blood glucose levels.  Glycolysis converts glucose to two pyruvate molecules, whereas gluconeogenesis consumes a net total of 6 NTPs (4 ATPs and 2 GTPs) to convert two pyruvate molecules back to glucose.  When glycolysis is upregulated, gluconeogenesis is downregulated, and vice versa.As shown in Figure 1, glycolysis and gluconeogenesis in the liver are largely regulated by the allosteric action of the small molecule fructose-2,6-bisphosphate (F2,6BP) on the enzymes phosphofructokinase-1 (PFK-1) and fructose-1,6-bisphosphatase (F1,6BPase).  PFK-1 is a kinase that uses ATP to phosphorylate fructose-6-phosphate (F6P) in an irreversible step of glycolysis, forming fructose-1,6-bisphosphate (F1,6BP) and ADP.  During gluconeogenesis, F1,6BPase removes the phosphate group by hydrolysis.Figure 1  Activities of (A) PFK-1 and (B) F1,6BPase on their respective substrates in the presence (solid lines) and absence (dashed lines) of F2,6BPA bifunctional enzyme that contains a phosphofructokinase-2 (PFK-2) domain and a fructose-2,6-bisphosphatase (F2,6BPase) domain controls F2,6BP levels in the liver.  The PFK-2 domain converts F6P to F2,6BP, and the F2,6BPase domain converts F2,6BP back to F6P.  When blood glucose levels are low, the enzyme becomes phosphorylated.  This phosphorylation event simultaneously activates the F2,6BPase domain and inactivates the PFK-2 domain.  Under high blood glucose conditions, the enzyme becomes dephosphorylated, activating the PFK-2 domain and inactivating the F2,6BPase domain.Question 13Which metabolic process most likely provides the energy necessary for sustained gluconeogenesis?A.Fatty acid oxidationB.GlycogenolysisC.FermentationD.Pentose phosphate pathway

Which two processes depend on glucose being able to exit the cell where they occur?Group of answer choicesfermentation and glycogenolysis in the musclegluconeogenesis and glycogenolysis in the liverglycolysis and gluconeogenesis in the liverglycolysis and glycogen synthesis in the liver

In the liver, insulin signalling up-regulates glycolysis. Which of the following signalling pathways explains that mechanism?Group of answer choicesIt activates protein phosphatase-1 which dephosphorylates glycogen phosphorylase.It results in the activation of cAMP dependent protein kinase A (PKA) which phosphorylates pyruvate kinase.It activates the expression of hexokinase, PFK-1 and pyruvate kinase.It results in an increased expression of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase.

some glucose bypasses liver to provide fuel for brain anderythrocytes• in hepatocytes– glucose is actively phosphorylated• by the action of glucokinase– glucose‐6‐phosphate may be converted to:• glycogen to replenish liver stores• glucose via glucose‐6‐phosphatase if blood glucose < 4 mM• pyruvate via glycolysis, hence to acetyl‐CoA, but fatty acids are preferredfuel for liver cells• PPP intermediates providing NADPH for reductive biosyntheses andpentose phosphates for nucleotide biosynthesis

In the liver, adrenaline signalling results inGroup of answer choicesDephosphorylation of glycogen synthase which decreases glycogenesis.The T state of Phosphofructokinase-1 is stabilised which increases glycolysis.Phosphorylation of the bifunctional PFK-2/FBPase-2 enzyme which increases glycolysis.Phosphorylation of glycogen phosphorylase which increases glycogenolysis.

Gluconeogenesis, must bypass irreversiblereactions of glycolysis, except:a. Hexokinaseb. Phosphohexose isomerasec. Pyruvate kinased. Phosphofructokinase