Cellular phosphorus utilization — which biosynthetic process directly incorporates inorganic phosphate? Phosphorus is taken up by cells and incorporated during which of the following processes most directly?

Introduction:
Phosphorus is essential in biology, commonly entering metabolism as inorganic phosphate (Pi). While phosphate becomes part of many biomolecules, one of the most direct, universal incorporations is the phosphorylation of ADP to ATP, the cell’s primary energy currency.

Given Data / Assumptions:

• ATP contains three phosphate groups linked by high-energy phosphoanhydride bonds.
• Cells continuously regenerate ATP from ADP and Pi via oxidative phosphorylation, photophosphorylation, or substrate-level phosphorylation.
• Other macromolecules (proteins, many carbohydrates, neutral lipids) do not directly incorporate free Pi as a dominant step.

Concept / Approach:

Identify the pathway where Pi is directly consumed. During ATP synthesis, inorganic phosphate is enzymatically joined to ADP to form ATP. Although phospholipid and nucleic acid synthesis also utilize phosphate, the most straightforward and universal uptake highlighted by the options is ATP generation.

Step-by-Step Solution:

Verification / Alternative check:

Biochemistry texts show ATP synthase (mitochondrial or bacterial) forming ATP from ADP and Pi; substrate-level phosphorylation reactions (e.g., in glycolysis) also transfer Pi-derived groups to ADP.

Why Other Options Are Wrong:

Carbohydrate synthesis of neutral polymers and protein synthesis do not directly incorporate free phosphate groups. Neutral triacylglycerol assembly lacks phosphate (phospholipids would, but that is not specified). Chlorophyll assembly is not the central, universal phosphate-incorporating pathway.

Common Pitfalls:

Confusing phospholipid synthesis with “lipid synthesis” broadly; only phospholipids contain phosphate, not all lipids.

Final Answer:

ATP synthesis (phosphorylation of ADP to ATP)