What defines cells in a biological context?

The definition of cells in a biological context is rooted in the understanding that they are the smallest structural units of living matter. Cells serve as the fundamental building blocks of all living organisms. This definition is a key aspect of the cell theory, which states that all living things are composed of one or more cells, and that the cell is the basic unit of life.

Cells encompass a vast array of structures and functions, making them essential for the existence of all forms of life, both unicellular and multicellular. They perform critical functions such as metabolism, growth, and reproduction, allowing organisms to thrive and adapt to their environments.

In contrast, the other options do not align with the accepted biological definition of cells. For instance, defining cells as the largest structural units of living matter would misrepresent the actual biological hierarchy, where cells are indeed much smaller than tissues, organs, and organisms as a whole. Stating that cells only compose plants restricts the scope of their definition, as cells are found in animals, fungi, and microorganisms as well. Lastly, suggesting that cells only exist in multicellular organisms overlooks the existence of single-celled organisms such as bacteria and protists, which are entirely composed of a single cell.