What term describes a membrane-enclosed structure with a specialized function within a cell?

The term that describes a membrane-enclosed structure with a specialized function within a cell is organelles. Organelles are distinct components within a cell, each performing specific tasks crucial to the cell's overall function and health. For example, mitochondria are organelles responsible for energy production, while the endoplasmic reticulum plays a key role in protein and lipid synthesis.

Cells, tissues, and organisms refer to larger biological structures. Cells are the basic units of life and contain organelles as part of their internal structure. Tissues are groups of similar cells that work together to perform a function, and organisms consist of multiple systems made up of different tissues and cells. Therefore, organelles specifically denote those specialized, membrane-bound structures within cells that enable diverse cellular functions.