C H A P T E R 7
Introduction to cell physiology
73
C
hemotherapeutic drugs are used to destroy both organ-
isms that invade the body (e.g. bacteria, viruses, parasites,
protozoa, fungi) and abnormal cells within the body (e.g.
neoplasms, cancers). These drugs affect cells by altering
cellular function or disrupting cellular integrity, causing
cell death, or by preventing cellular reproduction, eventu-
ally leading to cell death. Because most chemotherapeutic
agents do not possess complete
selective toxicity
, they
also, to some extent, affect the normal cells of people.
To understand the actions and adverse effects caused by
chemotherapeutic agents and to determine interventions
that increase therapeutic effectiveness, it is important to
understand the various properties and the basic structure
and function of the cell.
THE CELL
The cell is the basic structural unit of the body. The cells
that make up living organisms, which are arranged into
tissues and organs, all have the same basic structure.
Each cell has a nucleus, a cell membrane and cytoplasm,
which contains a variety of organelles (Figure 7.1).
Cell nucleus
Each cell is “programmed” by the
genes
, or sequences
of DNA, that allow for cell division, produce specific
proteins that allow the cell to carry out its functions and
maintain cell homeostasis or stability. The
nucleus
is the
part of a cell that contains all genetic material necessary
for cell reproduction and for the regulation of cellular
production of proteins. The nucleus is encapsulated in
its own membrane and remains distinct from the rest of
the cytoplasm. A small spherical mass, called the nucle-
olus, is located within the nucleus. Within this mass are
dense fibres and proteins that will eventually become
ribosomes
, the sites of protein synthesis within the cell.
Genes are responsible for the formation of messenger
RNA and transcription RNA, which are involved in
production of the proteins unique to the cell. The DNA
necessary for cell division is found on long strains called
chromatin. These structures line up and enlarge during
the process of cell division.
Cell membrane
The cell is surrounded by a thin barrier called the
cell
membrane
, which separates intracellular fluid from
extracellular fluid. The membrane is essential for cellular
integrity and is equipped with many mechanisms for
maintaining cell homeostasis.
Lipoproteins
The cell membrane is a
lipoprotein
structure,
meaning that it is mainly composed of proteins and
Rough
endoplasmic
reticulum
Smooth
endoplasmic reticulum
Polyribosomes
Golgi
apparatus
Cilia with
microtubules
Peroxisomes
Lysosomes
Nucleus:
Nuclear
membrane
Nuclear pore
Nucleolus
Cell membrane
Microtubules
Mitochondria
Centrioles
FIGURE 7.1
General structure of a cell and the
location of its organelles.
