Pathophysiology - Definition - What is cell and it functions?

The cell is the smallest functional unit that an organism
can be divided into and retain the characteristics necessary
for life. Cells with similar embryonic origin or
function are often organized into larger functional units
called tissues. These tissues in turn combine to form the
various body structures and organs. Although the cells
of different tissues and organs vary in structure and function,
certain characteristics are common to all cells. Cells
are remarkably similar in their ability to exchange materials
with their immediate environment, obtain energy
from organic nutrients, synthesize complex molecules,
and replicate themselves. Because most disease processes
are initiated at the cellular level, an understanding of cell
function is crucial to understanding the disease process.
Some diseases affect the cells of a single organ, others
affect the cells of a particular tissue type, and still others
affect the cells of the entire organism.

Figure 1-1 : composite cell designed to show in one cell all of the various components of the nucleus and cytoplasm.