The Cell - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 1

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The Cell

Manisha Lalan 1 , Tamishraha Bagchi 2 ,
Ambikanandan Misra 1
1 Pharmacy Department, TIFAC - Centre of Relevance and Excellence in New
Drug Delivery Systems, The Maharaja Sayajirao University of Baroda,
PO Box 51, Kalabhavan, Vadodara 390 001, Gujarat, India
2 Department of Microbiology and Biotechnology, Faculty of Science,
The Maharaja Sayajirao University of Baroda, Vadodara 390 001,
Gujarat, India

1.1 Introduction

The cell is the most fundamental and primary unit of life. These membrane-enclosed
units are composed of an aqueous sol and endowed with a unique capability of repli-
cation. Lower organisms are unicellular, whereas higher organisms like us are com-
munities of a wide variety of cells working in consortium to perform the essential
functions. Although all living cells exhibit a similar basic cellular chemistry, there is
enormous variance in the appearance and function of cells. Although the solitary cell
of unicellular organisms can perform all the vital functions, the cell groups in multi-
cellular organisms are differentiated to perform specific functions.
Cells have been classified as prokaryote, or primitive, and eukaryote, according to
a very basic fundamental feature: the absence or presence of a well-defined nucleus
that contains genetic information. Prokaryotes have been synonymous with bacteria.
Most prokaryotes live as unicellular organisms, but they also exhibit association in
the form of chains, clusters, and so on. These have been known to survive on almost
anything, from wood to petroleum, in the most extreme environmental conditions.
Oxygen is essential to some prokaryotes, but fatal for others. Although some can
perform photosynthesis, other prokaryotes are totally dependent on others for sur-
vival. Escherichia coli is one of the most widely studied bacterium, by scientists
seeking to understand the basic principles of life; E. coli is also used as a biotech-
nological tool.
Eukaryotic cells are larger and more complex than prokaryotes ( Fig. 1.1 ), but they
may also be unicellular or multicellular. They are characterized by a well-defined
nucleus. Apart from the nucleus, there are other organelles that are key to their sur-
vival and homeostasis. In general, the biochemical makeup and the organelles of the
cells are similar in fundamental ways. In this chapter, only major cellular organelles
that perform vital functions are discussed.