Cell - 1
A fundamental statement of life is that all organisms are composed of one or
The cell is the structural and functional unit of life.
A cell is the
simplest collection of matter that has the properties of life.
All living organisms
are composed of one or more cells.
For single-celled organisms, all requirements
for life: growth, development, regulation, reproduction, etc., are met within a
Multicellular plants, fungi and animals are comprised of collections of
cells and tissues, each with specialized structures and functions that contribute to
These two statements (Living organisms are composed of cells and
cells are the structural and functional unit of life) along with a third:
All cells come
from pre-existing cells form the
Each cell is unique, composed of molecules organized into an orderly structural and
Just as we saw that macromolecules are remarkable in their
structure to function relationship, we shall, in this chapter, see how the structure
of cells and, in particular, the structure of cell components, facilitates the
functioning of cells.
Much of what we will be discussing about cells was learned using methods we
cannot see with our un-assisted eyes.
Cells, for the most part, are microscopic.
Moreover, when we turn to the functioning of cells, and their component parts, the
organelles, we must often affect the very cell that we are hoping to learn about
with our manipulations.
Until the first light microscopes of 300 years ago, no one had really seen cells.
However, even the best light microscope can not clearly resolve images magnified
more than 1000x times (for detail about 0.2
There are a variety of methods
used to enhance the quality of images viewed with a light microscope, which, in
combination, can help researchers.
Until the use of transmission electron microscopes and scanning electron
microscopes during the past fifty or so years, many cell components that we
discuss today were not known or seen.
(Electron microscopes can resolve images
of about 2 nm.
The scanning-tunneling microscope can generate computer surface
images of single atoms magnified about 2 million times.)
BCC is fortunate to have
had a scanning electron microscope donated for student (and faculty) use by a
As mentioned, cell biologists frequently study cell components outside of the cell
using techniques such as cell fractionation, in which differential centrifugation is
used to separate and isolate different organelles based on their density.
you will have done a cell fractionation lab in Biology 101 or in other courses.
At any rate, in this chapter we are going to look at structure and organization of
typical cells, based on the knowledge we have of cells today.