T2.3_Gluconeogenesis_and_glycogen_synthesis

T2.3_Gluconeogenesis_and_glycogen_synthesis -...

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Gluconeogenesis and glycogen synthesis Learning objectives: To understand the physiological  significance of gluconeogenesis and to list  the primary precursors of gluconeogenesis To name the organs that carry out  gluconeogenesis To describe the enzymatic steps involved  in the conversion of  phosphoenolpyruvate  to pyruvate
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Learning objectives, contd. To describe the role of biotin and acetyl  CoA in the reaction catalyzed by pyruvate  carboxylase To identify the enzymes unique to  gluconeogenesis, i.e. those that do not  participate in glycolysis To outline the Cori cycle and to appreciate  it’s biological relevance
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Learning objectives, contd. Regarding glycogen synthesis: Describe the precursors of glycogen  anabolism Understand the role of hormones in  regulating glycogen metabolism
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Stoichiometry of gluconeogenesis 2 Pyruvate + 4 ATP + 2 GTP + 2 NADH + 6 H 2 O  -------- Glucose + 4 ADP + 2 GDP + 6 P i  + 2 NAD +   + 2 H + Six nucleotide triphosphate molecules are hydrolyzed to  synthesize glucose from pyruvate in gluconeogenesis while only  two molecules of ATP are generated in glycolysis in the  conversion of glucose to pyruvate. Thus, the extra cost of  gluconeogenesis is four high phosphoryl-transfer potential  molecules per molecule of glucose synthesized from pyruvate.  These extra high phosphoryl-transfer potential molecules  (Where do they come from? Can you think of a condition[s] that  will favor gluconeogenesis?) are essential to turn an  energetically unfavorable process (reversal of glycolysis) into a  favorable one. 
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Pathway of gluconeogenesis The distinctive reactions and  enzymes of this pathway are  shown in red. The other  reactions are common to  glycolysis. The enzymes for  gluconeogenesis are located  in the cytosol, except for  pyruvate carboxylase  (in  the mitochondria) and  glucose-6-phosphatase  (membrane bound in the  endoplasmic reticulum). The  entry points for lactate,  glycerol and amino acids are  shown.
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Mitochondrial and cytosolic compartments  cooperate to synthesize glucose from pyruvate
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T2.3_Gluconeogenesis_and_glycogen_synthesis -...

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