When Lipid Biosynthesis Is Active Using Carbohydrates as a Source $\rarr$

question 24

Multiple Choice

When lipid biosynthesis is active using carbohydrates as a source of carbon, three things are needed: NADPH, ATP and acetyl-CoA (from pyruvate) . Which of the following best explains the operation of the pentose phosphate pathway (PPP) under such conditions? G6P = glucose-6-phosphate, F6P = fructose-6-phosphate, G3P = glyceraldehyde-3-phosphate

• A)3 G6P \(\rarr\) 2 F6P + 1 G3P with the F6P recycled to G6P to re-enter the PPP while G3P continues through glycolysis to make acetyl-CoA and ATP
• B)6 G6P \(\rarr\) 4 F6P + 2 G3P with 1 G3P converted to DHAP, the other G3P + DHAP giving F6P with all F6P recycled to G6P to re-enter the PPP
• C)3 G6P \(\rarr\) 2 F6P + 1 G3P with the F6P and G3P continuing through glycolysis to make acetyl-CoA and ATP
• D)3 G6P \(\rarr\) 2 F6P + 1 G3P with all G3P continuing through glycolysis. Some F6P is recycled to G6P while some continues through glycolysis-the amount dependent upon the requirements for NADPH, ATP and acetyl-CoA
• E)none of the above

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