The structure within a human cell responsible for recycling materials no longer functioning is the lysosome.

Here's why:

* Lysosomes are the "recycling centers" of the cell. They contain powerful enzymes that break down worn-out organelles, cellular debris, and engulfed bacteria or viruses.

* They engulf and digest cellular waste: Lysosomes fuse with vesicles containing the material to be recycled, and the enzymes within break down the components into smaller molecules.

* These smaller molecules can then be reused by the cell: This process is crucial for maintaining cellular health and function.

Let me know if you'd like to know more about lysosomes or other cellular structures!