The Pentose Phosphate Pathway

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What is the major metabolic fate of glucose?
Glycolysis, link reaction then TCA cycle
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What is an alternate route?
Pentose phosphate pathway
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When does the PPP branch off from the major metabolic fate?
It branches off a from glycolysis with glucose-6P, so it starts off like glycolysis but then branches off at the second stage
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What does the PPP allow?
Synthesis of other metabolites and precursors of macromolecules
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What are the 2 stages of the PPP?
1) Oxidative stage (irreversible, oxidises glucose to ketopentose ribulose-5-phosphate), 2) Non-oxidative stage (reversible, interconverting 3C, 4C, 5C, 6C and 7C sugars)
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Why is hexokinase not the major control point?
Step 1 isn't a major control point because it is also part of the PPP, the control is just for glycolysis hence why the major control point is at step 3 instead of step 1
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Where does the PPP take place?
In the cytoplasm (cytoplasm and chloroplasts in plants)
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Step 1 of PPP- after glucose has been converted to glucose-6P (Oxidative stage)
Irreversible reaction, (Enzyme:Glucose-6P dehydrogenase), NADPH+H+ hydrogen carrier, cofactor: Mg2+, product: 6-phosphogluconolactone
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Step 2 (oxidative stage)
Cyclic bond hydrolysed, irreversible, (Enzyme: Lactonase), product: 6-Phosphogluconate
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Step 3 (oxidative stage)
Oxidation reaction, irreversible, (Enzyme: 6-phosphogluconate dehydrogenase), NADP+ hydrogen carrier, CO2 released, product: Ru5P
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Stage 4 (non-oxidative stage)
Interconvert between isomers, (Enzyme: Ribose-5P isomerase), product: Ribose P and Xylulose-5P
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Stage 5 (non-oxidative stage)
Interconvert between epimers, (Enzyme: Ribose-5P epimerase), product: Ribose-5P
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Stage 6 (non-oxidative stage)
Takes 2C unit from top ketose and adds it to aldose, reversible, (Enzyme: Transketolase), product: an aldose -2C (Sedohept-7P) and a ketose +2C (G3P)
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Stage 7 (non-oxidative stage)
Takes 3C unit from top ketose and gives it to an aldose, reversible, (Enzyme: Transaldolase), product: a ketose +3C (Fructose-6P) and an aldose -3C (Erythrose-4P)
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What molecules from the PPP are used for lipid synthesis?
The 2 NADPH+H+ molecules (One from stage 1, one from stage 3)
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What molecules from the PPP are used for central metabolism?
Xylose-5P, G3P and fructose-6P
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What molecule from the PPP is used for nucleotides?
Ribulose-P
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Which molecule from the PPP is used for aromatic amino acids?
Erythrose-4P
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Other cards in this set

Card 2

Front

What is an alternate route?

Back

Pentose phosphate pathway

Card 3

Front

When does the PPP branch off from the major metabolic fate?

Back

Preview of the front of card 3

Card 4

Front

What does the PPP allow?

Back

Preview of the front of card 4

Card 5

Front

What are the 2 stages of the PPP?

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