Introduction to the Study of Cell and Molecular Biology
o Cell and molecular biology is reductionist; based on the view that knowledge of the
parts of the whole can explain the character of the whole.
o Cells can only be observed with the aid of a microscope, which is an instrument that
provides a magnified image of a tiny object
o Robert Hooke, English microscopist, credited for the discovery of cells. One of the
many questions he attempted to answer was why stoppers made of cork were so well
suited to holding air in a bottle. He examined a cut piece of cork under a microscope
and perceived what appeared to be pores which he labeled as cells.
Ornate compound (double-lens) microscopes
o Anton van Leeuwenhoek, Dutchman, spent spare time grinding lenses and
constructing simple microscopes of remarkable quality. He was the first to examine a
drop of pond water under a microscope. He was able to observe teeming microscopic
animalcules that darted back and forth before his eyes. He was also the first to
describe various forms of bacteria, which he obtained from water in which pepper had
been soaked and from scrapings of his teeth.
o Matthia Schleiden, German lawyer turned botanist, concluded that despite
differences in structure of various tissues, plants were made of cells and that plant
embryo arose from a single cell. o Theodore Schwann, German zoologist, concluded that the cells of plants and animals
are similar in structures and proposed these two tenets of cell theory:
a. All organisms are composed of one of more cells.
b. The cell is the structural unit of life.
o By 1855, Rudolf Virchow, German pathologist, had made a convincing case for the
third tenet of the cell theory:
c. Cells can arise only by division from a preexisting cell.
o Life is the most basic property of cells, and cells are the smallest units to exhibit this
property. Unlike parts of cells which simply deteriorate if isolated, whole cells can be
removed from a plant or animal and cultured in a laboratory.
o Death can also be considered one of the most basic properties of life, because only
living entity faces this prospect. Cells within the body generally die by their own
hand the victims of an internal program that causes cells that are no longer needed
or cells that pose a risk of becoming cancerous to eliminate themselves.
o First culture of human cells was begun by George and Martha Gey. The cells were
obtained from a malignant tumour and named HeLa cells
These cells are so much simpler to study than cells situated within the body,
cells grown in vitro (i.e., in culture, outside the body) have become an
essential tool of cell and molecular biologists.
o Cells are highly complex and organized. The more complex a structure, the greater
the number of parts that must be in their proper place, the less tolerance of errors in
the nature and interactions of the parts, and the more regulation or control that must
be exerted to maintain the system.
o Each type of cell has a consistent appearance when viewed under a high-powered
electron microscope; its organelles have a particular shape and location, from one
individual of a species to another. These organelles have a consistent composition of
macromolecules, which are arranged in a predictable pattern.
o Many of the most basic processes, such as the synthesis of proteins, the conservation
of chemical energy, or the construction of a membrane, are remarkably similar in
Humans and a cat have very different anatomical features, the cells that make
up their tissues, and the organelles that make up their cells are very similar.
o Information obtained by studying cells from one type of organism often has direct
application to other forms of life.
o Cells possess a genetic program and the means it use it
Organisms are built according to information encoded in a collection of genes.
Genes are more than storage lockers for information: they constitute the
blueprints for constructing cellular structures, the directions for running
cellular activities, and the program for making more of themselves. Molecular structure of genes allows for changes in genetic information
(mutations) that lead to variation among individuals, which forms the basis of
o Cells are capable of producing more of themselves
Just as individual organisms are generated by reproduction, so too are
individual cells. Cells reproduce by division, a process in which the contents of
a mother cell are distributed into two daughter cells. The daughter cells
receive a complete and equal share of genetic information and both have
approximately equal volume.
In some cases however, human oocyte undergoes division, this allowing one of
the cells to retain nearly all of the cytoplasm, even though it received only half
of the genetic material.
o Cells acquire and utilize energy
Every biological process requires the input of energy. Virtually all of the energy
utilized by life on the Earths surface arrives in the form of electromagnetic
radiation from the sun.
Energy of light is trapped by light-absorbing pigments present in the
membranes of photosynthetic cells. This energy is then converted by
photosynthesis into chemical energy that is stored in energy-rich carbohydrate,
such as sucrose or starch.
For most animal cells, energy arrives prepackaged, often in the form of sugar
glucose. In humans, glucose is released by the