Introduction
to the Cell
All
living organisms are composed of cells. A cell is a small, membrane-bound
compartment that contains all the chemicals and molecules that help support an
organism's life. An understanding of the structure of cells is one of the first
steps in comprehending the complex cellular interactions that direct and
produce life.
Cells can be thought of as building blocks of
organisms. Some organisms are composed of a single cell. Others, like
ourselves, are composed of millions of cells that work together to perform the
more complex functions that make us different from bacteria.
It is difficult to imagine that humans are descendants of a single cell, but
this is a common belief in the scientific world. Before we can understand how
multiple cells can work together to create complex biological functions, it is
necessary to understand what biological functions single cells are capable of
performing on their own to sustain life.
There are different types of cells with
individuated structures. Single-celled organisms have different cell structure
than multi-celled organisms and plant cells have different structures from
animal cells. These differences reflect differences in the functions that each
of these classes of cells is required to perform. While the focus of this guide
will be on the structures that compose complex multi-cellular organisms, we
will begin our discussion of cell structure with a structure that is universal
to all cells, membranes.
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