Which is an component of the modern cell theory that was not part of the original cell theory?

The modern cell theory states that living organisms are made of cells, that all cells come from other cells and that cells are the most basic life form. As scientific advancements are made, definitions of theories, like the cell theory, are updated. The modern cell theory is not the same as cell theory of the past.

"All cells are similar in composition and metabolic activities."

Explanation:

Cell Theory is the key theory for the study of Cell Biology, as it refers to the cellular composition of living things. The cellular theory is composed by the ideas of Schwann, Schleiden and Virchow and was based on three basic ideas:

All living organisms are formed by one or more cells and the structures they produce; Cells are considered morphological and functional units of all life forms; All cells originate from another pre-existing cell, ie all cells are capable of division.

Schwann, Schleiden, and Virchow, however, believed that all cells were similar in composition and metabolic activity and included this idea in cell theory. However, over the years and the advancement of technology this thinking has been discredited and today, current cellular theory, asserts that not all cells are similar in composition or metabolic activity.