Glycolysis Flashcards
Major pathway for glucose metabolism that converts glucose into 3 carbon compounds to provide energy
Glycolysis
Site of glycolysis
CYTOSOL
Substrate of glycolysis
GLUCOSE
End products of glycolysis
2 molecules of either pyruvate or lactate
Step that is Rate Limiting
Fructose 6 phosphate –> Fructose 1,6-bisphosphate
PHOSPHOFRUCTOKINASE
3 Important Steps in Glycolysis
Step 1: Phosphorylation of glucose
Step 2: Phosphorylation of fructose 6-phosphate
Step 3: Formation of Pyruvate
Found in most tissues
Inhibited by glucose 6-phosphate
LOW Km, HIGH affinity
LOW Vmax
Hexokinase
Found in LIVER and ISLET cells of PANCREAS
Inhibited by fructose 6-phosphate
HIGH Km, LOW affinity
HIGH Vmax
Liver activity induced by insulin
Glucokinase
acts only when glucose is very high >100 mg/dL
Most POTENT activator of PFK-1
Fructose 2,6 BP
2 steps in glycolysis that produce ATP via substrate level phosphorylation
1,3 bisphosphoglycerate –> 3 phosphoglycerate
PHOSPHOGLYCRTAE KINASE
Phosphoenolpyruvate –> pyruvate
PYRUVATE KINASE
Oxidation reaction that passes electrons to NAD+ to make NADH
Glyceraldehyde-3-phosphate –> 1,3 bisphosphoglycerate
GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE
Major fate of pyruvate in lens, cornea, kidney (medulla), testes, RBCs, WBCs
Anaerobic glycolysis
pyruvate –> LACTATE
lactate dehydrogenase
NADH - used to REDUCE pyruvate to lactate
No. of ATPs from Aerobic glycolysis
7 ATPs
No. of ATPs from anaerobic glycolysis
2 ATPs
Cells w/ mitochondria
Cells w/ adequate O2 supply
Aerobic Glycolysis
END PRODUCT: Pyruvate
Cells w/o mitochondria
Cells w/o adequate O2 supply
Anaerobic Glycolysis
END PRODUCT: Lactate
Number of ATPs generated
From Aerobic Glycolysis - 7 ATP
From Pyruvate Dehydrogenase - 2 NADH = 5 ATP
From TCA cycle (2 acetyl CoA from 1 mol of glucose) - 2x10 = 20 ATP
NET ATP = 7+5+20 = 32 ATP
Found in RBCs where the reaction catalyzed by phosphoglycerate kinase is bypassed
RAPAPORT LUEBERING SHUNT PATHWAY
1,3 BPG –> 2,3 BPG
BIPHOSPHOGLYCERATE MUTASE
Fates of Pyruvate
To Glucose (Gluconeogenesis)
To Lactate (Lactate dehydrogenase)
To Oxaloacetate (Pyruvate Carboxylase)
To Acetyl CoA (Pyruvate Dehydrogenase)
To Alanine (Alanine Amino Transferase)
Coenzymes of PYRUVATE DEHYDROGENASE COMPLEX
Pyruvate –> Acetyl CoA
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Thiamine pyrophosphate Lipomide Coenzyme A (Pantothenic acid) FAD NAD+
MC enzyme defect in glycolysis
Pyruvate kinase
HEMOLYTIC ANEMIA
MCC of congenital LACTIC ACIDOSIS
Pyruvate dehydrogenase deficiency
x-linked dominant
increased lactate + decreased acetyl CoA –> psychomotor retardation and death
TREATMENT: ketogenic diet
Fate of Acetyl CoA
FA Synthesis
Ketone Body Synthesis
Cholesterol Synthesis
TCA cycle
CANNOT BE CONVERTED TO GLUCOSE
Coenzyme Prosthetic Groups
Thiamine diphosphate of E1 (pyruvate decarboxylase)
Lipoic acid of E2 (dihydrolipoyl transacetylase)
FAD of E3 (dihydrolipoyl dehydrogenase)
Coenzyme Cosubstrates Groups
CoA
NAD+
The MC form of PDHC deficiency is caused by mutations to
Thiamine diphosphate of E1 (pyruvate decarboxylase)
End products that INHIBIT PDH COMPLEX
Acetyl CoA
NADH
Covalent modification of PDH Complex
ACTIVE in DEphosphorylated state
INACTIVE in PHOsphorylated state
PDH is PHOSPHORYLATED (inactivated) by
PDH KINASE -activated in increase in ATP/ADP Acetyl CoA/CoA NADH/NAD
PDH is DEPHOSPHORYLATED (activated) by
PDH PHOSPHATASE
-activated by INSULIN
