Why is a carboxylation and a decarboxylation required to form phosphoenolpyruvate from pyruvate?

E3 of the pyruvate dehydrogenase complex performs which main function?  A)  removing a proton from TPP forming a carbanion  b)  catalyzing the condensation of the TPP carbanion with pyruvate to form hydroxyethyl-TPP c) oxidation and transfer of the hydroxyethyl group to lipoic acid  d)  reoxidation of lipoic acid in order to keep the reaction going Once acetyl-CoA is formed, it usually takes one of two paths. The first is further oxidation in the citric acid cycle. The second is: a) conversion to oxaloacetate which generates glucose by gluconeogenesis   b)  synthesis of galactose  c) activates transcription factors which signal the synthesis of peptidase enzymes d) it is used in the synthesis of fatty acids.

The free energy of hydrolysis of an α(1→4) glycosidic bond is −15.5 kJ ⋅mol−1, whereas that of an α(1→6) glycosidic bond is −7.1 kJ ⋅ mol−1. Use these data to explain why glycogen debranching includes three reactions [breaking and re-forming α(1→4) bonds and hydrolyzing α(1→6) bonds], whereas glycogen branching requires only two reactions [breaking α(1→4) bonds and forming α(1→6) bonds].

Which of the following is a true statement regarding sphingolipid synthesis? (A) The first step in sphingolipid synthesis is the condensation of palmitoyl CoA with aspartate to form b-ketosphinganine.(B) This process requires the reduction of a ketone that uses NADH as the reducing agent.(C) A fatty acid is attached to dihydrosphingosine to form dihydroceramide. (D) FAD is using as an oxidizing agent to remove a double bond from dihydroceramide.(E) The formation of sphingomyelin requires the attachment of a glucose or galactose molecule to ceramide.

When the activated form of alcohol is used to synthesize glycerophospholipids, CDP-alcohol reacts with diacylglycerol to form glycerophospholipids. In this metabolic pathway, diacylglycerol is most likely produced by: a) Triacylglycerol lipase b) Phosphatidate phosphorylase c) Diacylglycerol lipase d) All of the above e) None of the above

How many NTP molecules are required to synthesize glucose from each of the following compounds? (a) Glucose 6-phosphate (b) Fructose 1,6-bisphosphate (c) Two molecules of oxaloacetate (d) Two molecules of dihydroxyacetone phosphate