Cell - 1
Just as the atom is the fundamental unit of matter, the cell is the fundamental
unit of living organisms.
Each cell is unique, composed of carbohydrates, proteins,
lipids, and other substances, organized into an orderly structural and functional
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.
History of the cell
The study of cells dates back more than three hundred years, coinciding with the
development of microscopes.
As scientists over the years learned more about
cells, a group of common characteristics was developed which we call the Cell
Our use today of more sophisticated microscopes and research on
biochemical cell activities reinforces these premises.
The Cell Theory
Every living organism is made up of one or more cells.
Cells are the structural and functional unit of living organisms.
living organisms are single cells, and cells comprise the functional units of
All cells arise from preexisting cells ensuring the continuity of life.
Basic Cell Features (Common to All Cells)
Plasma (cell) membrane
The plasma membrane is the boundary between the cell and its environment.
The plasma membrane isolates the cell, regulates what enters and leaves the cell,
and allows for interaction with other cells.
The plasma membrane is comprised of
phospholipid layers with proteins embedded throughout.
The diversity of proteins
found within membranes are responsible for most membrane activity. We will
discuss membrane structure and function a bit later.
nucleus or nucleoid
Each cell contains genetic material (DNA), which stores the instructions for that
cell's structure and function.
DNA may be found within a membrane - bounded
nucleus, (eukaryotic organisms – plants, animas, protists and fungi) or simply
concentrated in a region of the cytoplasm called the nucleoid (prokaryotic
organisms - Eubacteria and Archaebacteria).
Cytoplasm includes the fluid matrix (called the cytosol) inside the plasma
membrane in which everything else in the cell, such as internal membranes,
particles and membrane-bounded structures, called organelles, are suspended.