**Core Concept**
Purine nucleotide synthesis is a complex biochemical pathway that generates purine nucleotides, including adenine and guanine, from simpler precursors. This process is crucial for the synthesis of DNA and RNA, and it is tightly regulated to ensure proper cell growth and division.

**Why the Correct Answer is Right**
Purine nucleotide synthesis originates from ribose-5-phosphate, which is derived from glucose through the pentose phosphate pathway. The first committed step in purine synthesis is the formation of 5-phosphoribosyl-1-pyrophosphate (PRPP) from ribose-5-phosphate, catalyzed by the enzyme ribose-phosphate diphosphokinase. PRPP then serves as the precursor for the synthesis of inosine monophosphate (IMP), which is subsequently converted to adenine and guanine nucleotides.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the correct precursor for purine nucleotide synthesis. While glucose is a carbohydrate source for many metabolic pathways, it is not the direct precursor for purine synthesis.
**Option B:** This option is incorrect because it does not accurately represent the first committed step in purine synthesis. Although ribose-5-phosphate is a crucial intermediate, the formation of PRPP is the specific step that commits the pathway to purine synthesis.

**Clinical Pearl / High-Yield Fact**
A key regulatory mechanism in purine synthesis is the feedback inhibition of PRPP synthetase by purine nucleotides. This ensures that purine synthesis is tightly controlled and only occurs when necessary, preventing excessive accumulation of purine nucleotides that could lead to cell damage.

**Correct Answer: D. Ribose-5-phosphate**