The smallest structural unit that exhibits the characteristics of living things is

The smallest structural unit that exhibits the characteristics of living things is CELL.

Explanation:

Cell has been defined as the smallest unit of life. It can be found in all living things although the number may differ. Unicellular organisms have only one cells while multi cellular organisms have many cells. In unicellular organisms, a single cell perform all the necessary metabolic activities; in multi cellular organisms, cells are differentiated into different types that perform specific functions. When group of cells work together to perform a specific function they are called tissue. Aggregation of tissues is called organ while aggregation of organs is called systems.

Cell is the smallest structural unit of life. All living things in the world are made of small self-contained units called cells. Each cell is a collection of living matter enclosed by a cell membrane which function as a barrier that separate the cell from its surroundings. Most cells can perform all the functions associated with life.

Explanation: Living things have a level of complexity and organization not found in lifeless objects. These units generally too small to be seen with the naked eye, are organised into tissues. The organisms consisting of only a single cell are called "unicellular". Most of the organisms you are familiar with, however are multicellular, meaning they are made of many cells.

the endomembrane system i think