Major metabolic pathway through which monosaccharides are oxidised
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What is the starting products of glycolysis?
Glucose (and other monosaccharides)
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What is the product of glycolysis?
2 pyruvate molecules per 1 molecule of glucose
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Is glycolysis aerobic or anaerobic?
Can be either
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What is step 1 of glycolysis?
Phosphorylation of glucose, 1 ATP needed per glucose, (Enzyme: Hexokinase, Cofactor:Mg2+), irreversible reaction, product: Glucose-6P
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Step 2
Isomerisation of G6P to fructose-6-P, (Enzyme: Phosphoglucose isomerase), reversible reaction, product: Fructose-6-P
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Step 3
Phosphorylation of fructose-6-p, (Enzyme: Phosphofructose kinase), irreversible, 1 ATP hydrolysed, product: Fructose-1,6-Bisphosphate
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Step 4
Cleaving Fructose-1,6-Bisphosphate, splitting the C3-C4 bond, (Enzyme: Aldolase), reversible, product: Ketose phosphate (DHAP) and aldose phosphate (G3P)
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Step 5
Isomerisation of DHAP to G3P, interconverting of 2 trioses, (Enzyme: Triosephosphate isomerase), reversible, Product: 2 G3P molecules
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Where do the 2 G3P molecules come from?
1 G3P from fructose-1,6-BisP through aldose, 1 G3P from ketose phosphate (DHAP) through triode phosphate isomerase
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What happens to the 2 G3P molecules?
They both undergo the rest of glycolysis individually, hence why there are 2 pyruvate molecules as the product
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Step 6
Oxidation and phosphorylation of G3P, H removed during oxidation to H carrier coenzyme NAD+, the aldehyde group of G3P is oxidised then phosphorylated, (Enzyme: Glyceraldehyde-3-phosphate dehydrogenase), reversible, product: 1,3-bisphosphategycerate
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What else is produced from the phosphorylation and oxidation?
1 NAD+ reduced per G3P, (1NADH molecule produced)
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Step 7
Substrate level phosphorylation, (Enzyme: Phosphoglycerate kinase), reversible, Product: 3-phosphoglycerate (3-PGA) and 1 ATP molecule
Substrate level phosphorylation, (Enzyme: Pyruvate kinase), irreversible, cofactor MG2+, product: pyruvate, 1ATP per PEP
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How much ATP is produced from glycolysis?
8 ATP (2 from substrate level phosphorylation, 6 from oxidative phosphorylation) - 4 molecules of ATP per G3P molecule
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Describe the major control point at step 3
Regulation of phosphofructose kinase- ATP binds to both allosteric and active sites, allosteric site binding lowers affinity for fructose-6P, so there is lower activity
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Describe the control point at step 1
Inhibition of hexokinase, inhibited by glucose-6P, an increase of G6P means lower enzyme activity so less glucose is taken into the cell
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Describe the control point at step 10
Inhibition of pyruvate kinase, allosteric activation by fructose-1,6-bisphosphate, allosteric inhibition by ATP
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