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Regulation
Regulation of Carbohydrate Metabolism
| Question | Answer |
|---|---|
| What allosterically inhibits phosphofructokinase (PFK)? | ATP, decreased/low pH, citrate |
| What allosterically stimulates phosphofructokinase (PFK)? | AMP, fructose 2,6-bisphosphate (F-2,6-BP) |
| How is phosphofructokinase 2 activated? | dephosphorylation |
| How is fructose bisphosphatase 2 activated? | phosphorylation |
| How is phosphofructokinase 2 inactivated? | phosphorylation |
| How is fructose bisphosphatase 2 inactivated? | dephosphorylation |
| What is phosphofructokinase 2 stimulated by? (metabolic intermediate) | fructose 6-phosphate |
| What is fructose bisphosphatase 2 inhibited by? (metabolic intermediate) | fructose 6-phosphate |
| What inhibits hexokinase? | glucose 6-phosphate (product) |
| What allosterically stimulates L-form pyruvate kinase? | fructose 1,6 bisphosphate |
| What allosterically inhibits L-form pyruvate kinase? | ATP, alanine |
| How is L-form pyruvate kinase inhibited hormonally? | cAMP phosphorylation |
| How is L-form pyruvate kinase activated hormonally? | dephosphorylation |
| What allosterically inhibits pyruvate dehydrogenase complex? | ATP, NADH, acetyl CoA, long-chain fatty acids |
| What allosterically stimulates pyruvate dehydrogenase complex? | AMP, CoA, NAD+ |
| How is pyruvate dehydrogenase complex regulated by covalent modification? | phosphorylation/dephosphorylation of Ser on pyruvate dehydrogenase (E1) |
| In terms of covalent modification of pyruvate dehydrogenase complex, what allosterically activates protein kinase? | Acetyl CoA, NADH, ATP |
| In terms of covalent modification of pyruvate dehydrogenase complex, what allosterically inhibits the protein kinase? | pyruvate |
| In terms of covalent modification of pyruvate dehydrogenase complex, what allosterically stimulates the phosphoprotein phosphatase? | Ca2+ |
| What is the positive allosteric modulator for pyruvate carboxylase? | acetyl CoA |
| What is citrate synthase stimulated by? | ADP |
| What is citrate synthase inhibited by? | ATP, succinyl CoA, citrate, NADH |
| What is isocitrate dehydrogenase stimulated by? | Ca2+, ADP |
| What is isocitrate dehydrogenase inhibited by? | ATP |
| What is alpha-ketoglutarate dehydrogenase stimulated by? | Ca2+ |
| What is alpha-ketoglutarate dehydrogenase inhibited by? | succinyl CoA, NADH |
| What is the first coordinated control point of gluconeogenesis? | pyruvate -> PEP |
| What is the second coordinated control point of gluconeogenesis? | fructose 1,6-bisphosphate -> fructose 6-phosphate |
| What inhibits fructose 1,6 bisphosphatase? | fructose 2,6-bisphosphate, AMP |
| Why is fructose 2,6-bisphosphate important in regulation? | 1) fructose 2,6-bisphosphate stimulates PFK1, 2) inhibits fructose 1,6 bisphosphatase, 3) signal molecule present at low conc. during starvation |
| What is increased because of adenylate cyclase? | cAMP, which activates protein kinase A (PKA) |
| (fill in with arrows) low blood glucose: _blood glucagon, _cAMP-dependent phosphorylation of this bifunctional enzyme, _PFK2 and _FBPase 2, which then _F 2,6-BP, and then _PFK1 and _Fructose 1,6-bis-phosphatase | low blood glucose: increase blood glucagon, increase cAMP-dependent phosphorylation of this bifunctional enzyme, decrease PFK2 and increase FBPase 2, which then decrease F 2,6-BP, and then decreases PFK1 and increases Fructose 1,6-bis-phosphatase |
| How does glucagon stimulate gluconeogenesis? | decrease concentration of fructose 2,6-bisphosphate in liver |
| (fill in with arrows) glucagon: _adenylate cyclase, _cAMP-dependent protein kinase, _phosphorylation of PFK2/fructose bisphosphatase 2, _kinase activity, _phosphatase activity, leads to _of fructose 2,6-BP | glucagon: increases adenylate cyclase, increases cAMP-dependent protein kinase, increases phosphorylation of PFK2/fructose bisphosphatase 2, decreases kinase activity, increase phosphatase activity, leads to decrease of fructose 2,6-BP |
| Glucagon induces synthesis of which enzymes? | PEP-carboxykinase, fructose 1,6-bisphosphatase, glucose 6-phosphatase, certain aminotransferases |
| Glucagon represses synthesis of which enzymes? | glucokinase, PFK1, pyruvate kinase |
| Which reactions involved in carbohydrate metabolism are directly regulated by phosphorylation? | 1)fructose 6-phosphate -> fructose 1,6 bisphosphate (PFK1/FBPase2), 2) PEP -> pyruvate (pyruvate kinase), 3&4) glycogen -> glucose 1-phosphate + glycogen (n-1) (glycogen phosphorylase & phosphorylase kinase), 5)pyruvate ->acetyl CoA (PDH) |
| How is phosphorylase b allosterically activated in skeletal muscle? | AMP |
| Allosterically, how is phosphorylase b activation prevented? (skeletal muscle) | ATP, glucose 6-phosphate |
| Do different levels of AMP, ATP, and glucose 6-phosphate effect phosphorylase a? (skeletal muscle) | No, phosphorylase a is active regardless of these levels. |
| What hormones increase the formation of the active phosphorylase a form? (skeletal muscle) | epinephrine, glucagon |
| How is allosteric regulation of glycogen phosphorylase in the liver different from regulation in skeletal muscle? | 1) AMP does not activate liver phosphorylase b, 2) liver phosphorylase a is deactivated by glucose |
| What enzyme (specific) acts as a glucose sensor in the liver, slowing glycogen breakdown when bood glucose is high? | liver glycogen phosphorylase a |
| What can activate phosphorylase kinase? | phosphorylation, low levels of Ca2+ |
| How is the inactive b form of glycogen synthase activated? | dephosphorylation |
| Where is epinephrine found? | muscle and liver |
| Where is glucagon found? | liver |
| What hormonally stimulates the activity of phosphoprotein phosphatase in the regulation of glycogen synthase? | insulin |
| What is the rate-limiting step of the pentose phosphate pathway? | glucose 6-phosphate ->6-phosphoglucono-delta-lactone (glucose 6-phosphate dehydrogenase) |
| What is a competitive inhibitor of glucose 6-phosphate dehydrogenase? | NADPH |
| (fill in with arrows) Low blood glucose: _glucagon, _insulin, _PKA, _phosphorylase kinase, _glycogen phosphorylase, _glycogen synthase, _glycogen breakdown, _glycogen synthesis | Low blood glucose: increase glucagon, decrease insulin, increase PKA, increase phosphorylase kinase, increase glycogen phosphorylase, decrease glycogen synthase, increase glycogen breakdown, decrease glycogen synthesis |
| (fill in with arrows) High blood glucose: _insulin, _glucagon, _phosphoprotein phosphatase, _phosphorylase kinase, _glycogen phosphorylase, _glycogen synthase, _glycogen breakdown, _glycogen synthesis | High blood glucose: increase insulin, decrease glucagon, increase phosphoprotein phosphatase, decrease phosphorylase kinase, decrease glycogen phosphorylase, increase glycogen synthase, decrease glycogen breakdown, increase glycogen synthesis |
Created by:
chjung
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