Glucose Metabolism Flashcards
where does glycolysis take place?
cytosol
what is the purpose of glycolysis?
- energy producing pathway when oxygen is limiting
2. generates precursors for biosynthesis
what precursors does glycolysis produce?
- glucose-6-phosphate
- pyruvate
- glycerol-3-phosphate
Summarise the steps of glycolysis
glucose glucose-6-phosphate fructose-6-phosphate fructose-1,6-biphosphate glyceraldehyde-3-phosphate (+ dihydroxyacetone phosphate) 1,3-biphosphoglycerate 3-phosphoglycerate 2-phosphoglycerate phosphoenolpyruvate pyruvate
what steps of glycolysis are irreversible?
- glucose -> G6P
- F6P -> F-1,6,-P
- phosphoenolpyruvate -> pyruvate
which enzymes catalyse:
glucose -> G6P
- hexokinase
2. glucokinase
which enzyme catalyses:
G6P -> F6P
phosphoglucose isomerase
which enzyme catalyses:
F6P -> F-1,6-P
phosphofructokinase-1
which enzyme catalyses:
F-1,6-P -> glyceraldehyde-3P (+ dihydroxyacetone phoshate)
aldolase
which enzyme catalyses:
glyceraldehyde-3P = dihydroxyacetone phosphate
triose phosphate isomerase
which enzyme catalyses:
glyceraldehyde-3P -> 1,3-biphosphoglycerate
glyceraldehyde-3-phosphate dehydrogenase
which enzyme catalyses:
1,3-biphosphoglycerate -> 3-phosphoglycerate
phosphoglycerate kinase
which enzyme catalyses:
3-phosphoglycerate -> 2-phosphoglycerate
phosphoglyceromutase
which enzyme catalyses:
2-phosphoglycerate -> phosphoenolpyruvate
enolase
which enzyme catalyses:
phosphoenolpyruvate -> pyruvate
pyruvate kinase
which steps in glycolysis use ATP?
- glucose -> G6P
2. F6P -> F-1,6-P
which steps in glycolysis produce ATP?
- 1,3-biphosphoglycerate -> 3-phosphoglycerate
2. phosphoenolpyruvate -> pyruvate
what is the summary equation for glycolysis?
glucose + 2NAD+ + Pi + 2ADP -> 2pyruvate + 2NADH + 2H+ + 2ATP + 2H2O
what happens to the pyruvate from glycolysis in anaerobic conditions?
- catalysed by lactate dehydrogenase to form lactate
- NAD+ is regenerated
what happens to pyruvate from glycolysis in aerobic conditions?
- enters mitochondria
- converted to acetyl CoA + CO2 by pyruvate dehydrogenase
- acetyl CoA enters the Krebs cycle
where does the Krebs cycle take place?
mitochondrial matrix
what is the energy gain from the Krebs cycle?
6 NADH
2 FADH
2 ATP
Summarise the Krebs cycle
acetyl-CoA citrate isocitrate alpha-ketoglutatate succinyl-CoA succinate fumarate malate oxaloacetate citrate
what can produce the acetyl-CoA needed for the Krebs cycle?
- acetate
- pyruvate
- ketone bodies
- amino acids
what enzyme catalyses:
acetyl-CoA -> citrate
citrate synthase
what enzyme catalyses:
citrate -> isocitrate
aconitase
what enzyme catalyses:
isocitrate -> alpha-ketoglutarate
isocitrate dehydrogenase
what enzyme catalyses:
alpha-ketoglutarate -> succinyl-CoA
alpha-ketoglutarate dehydrogenase
what enzyme catalyses:
succinyl-CoA -> succinate
succinyl-CoA thiokinase
what enzyme catalyses:
succinate -> fumarate
succinate dehydrogenase
what enzyme catalyses:
fumarate -> malate
fumarase
what enzyme catalyses:
malate -> oxaloacetate
malate dehydrogenase
which step in the Krebs cycle produces ATP and GTP?
succinyl-CoA -> succinate
what is the overall reaction for the Krebs cycle?
Acetyl-CoA + 3NAD+ + FAD + GDP + Pi + 2H2O -> 2CO2 + 3NADH + FADH2 + GTP + 3H+ + CoA
where does oxidate phosphorylation take place?
inner mitochondrial membrane
summarise oxidative phosphorylation
- components of the ETC accept electrons (reduced) and pass them on (oxidised)
- electrons are transferred to their final electron acceptor (O2)
- the free energy is used to power the movement of H+ across the inner membrane space, creating a proton motive gradient
- ATP produced as protons flux through ATP synthase
what are the rate limiting steps of glycolysis?
- glucose -> G6P (hexokinase)
- F6P -> F-1,6-BP (PFK-1)
- phosphoenolpyruvate -> pyruvate (pyruvate kinase)
what are the rate limiting steps in the Krebs cycle?
- acetyl-CoA -> citrate (citrate synthase)
- isocitrate -> alpha-ketoglutarate (isocitrate dehydrogenase)
- alpha-ketoglutarate -> succinyl-CoA (alpha-ketoglutarate dehydrogenase)
which steps in the Krebs cycle produce NADH?
- isocitrate -> a-ketoglutarate
- a-ketoglutarate -> succinyl CoA
- malate -> oxaloacetate
- pyruvate -> acetyl CoA
what steps in the Krebs cycle produce FADH?
succinate -> fumarate