How are catabolism and anabolism coupled?

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Energy from catabolic reactions powers biosynthesis, and catabolism also supplies the building blocks that anabolic pathways need. When nutrients are broken down, cells generate ATP and reducing power, and they produce key intermediates that serve as precursors for making lipids, nucleotides, proteins, and carbohydrates. Anabolic processes then use that ATP (and reducing power, like NADPH) along with those precursors to assemble macromolecules. Because of this, the two sides of metabolism are tightly linked: the energy released from breakdown fuels the construction of cellular components, and the same metabolic intermediates feed both directions. For example, acetyl-CoA from catabolic pathways provides the building block for fatty acid synthesis, while the pentose phosphate pathway supplies NADPH and ribose-5-phosphate for nucleotide and lipid biosynthesis. Statements that catabolism consumes ATP, that anabolism directly makes ATP, or that the two operate completely independently don’t reflect how metabolism coordinates energy flow and building blocks.