To help understand how the pentose phosphate pathway functions it can be divided

Question

To help understand how the pentose phosphate pathway functions it can be divided into two parts. The oxidative part and the nonoxidative part of the pentose phosphate pathway both have specific characteristics and roles. Determine if each statement applies to the oxidative part, the nonoxidative part, both parts, or neither part.

1) Contains reactions that are very exergonic under cellular conditions.

2) Takes place in the cytosol.

3) Can be used to produce ribose 5-phosphate.

4) Uses oxidoreductases.

5) Produces ATP.

6) Oxidizes NADPH.

Explanation / Answer

1) Contains reactions that are very exergonic under cellular conditions.

Only the oxidative pathway is exergonic as it contains oxidative reactions which release energy.

2) Takes place in the cytosol.

Both the oxidative and non-oxidation pathways take place in the cytosol for most organisms. Cytosol is where the fatty acid synthesis takes place.

3) Can be used to produce ribose 5-phosphate.

Only the non-oxidative pathway can be used to generate ribose -5- phosphate. The first step in the non-oxidative pathway is conversion of ribulose-5-phosphate to ribose-5-phosphate.

4) Uses oxidoreductases.

Oxidoreductases are used only in the oxidative phase, since the non-oxidative phase does not have oxidation/reduction steps.

5) Produces ATP.

ATP is neither used nor produced in both the oxidative and non-oxidative steps.

6) Oxidizes NADPH.

Oxidation of NADPH takes place only in the oxidative phase, which then drives the reductional steps of the pathway.

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