**Core Concept**
The Pentose phosphate pathway (PPP) is a metabolic pathway that generates NADPH and pentoses from glucose-6-phosphate. It plays a crucial role in biosynthetic reactions, antioxidant defense, and redox balance in cells.

**Why the Correct Answer is Right**
The Pentose phosphate pathway produces several key molecules, including NADPH, ribose-5-phosphate, and erythrose-4-phosphate. NADPH is essential for fatty acid synthesis, cholesterol synthesis, and antioxidant defense. Ribose-5-phosphate is a precursor for nucleotide synthesis, while erythrose-4-phosphate is involved in aromatic amino acid synthesis. However, one molecule is not a product of the Pentose phosphate pathway.

**Why Each Wrong Option is Incorrect**
**Option A:** **Ribose-5-phosphate** is a product of the Pentose phosphate pathway, serving as a precursor for nucleotide synthesis. This option is incorrect because it is indeed a product of the PPP.
**Option B:** **Erythrose-4-phosphate** is also a product of the Pentose phosphate pathway, involved in aromatic amino acid synthesis. This option is incorrect because it is indeed a product of the PPP.
**Option C:** **NADPH** is a key product of the Pentose phosphate pathway, essential for fatty acid synthesis and antioxidant defense. This option is incorrect because it is indeed a product of the PPP.

**Clinical Pearl / High-Yield Fact**
The Pentose phosphate pathway is a crucial regulator of redox balance in cells, producing NADPH to counteract oxidative stress.

**Correct Answer: D.**