What
is Biophysics?
Biophysics is that branch of knowledge that applies the principles of
physics and chemistry and the methods of mathematical analysis and computer
modeling to understand how biological systems work.
Biophysics is a molecular science. It seeks to explain biological function
in terms of the molecular structures and properties of specific molecules.
The size of these molecules varies dramatically, from small fatty acids and
sugars (~1 nm = 10-9 m), to macromolecules like proteins (5-10 nm), starches
(>1000 nm), and the enormously elongated DNA molecules (over 10,000,000 nm =
1 cm long but only 2 nm wide; imagine a piece of string 45 miles long!).
These molecules, the sole building blocks of living organisms, assemble into
cells, tissues, and whole organisms by forming complex individual structures
with dimensions of 10, 100, 1000, 10,000 nm and larger. Proteins assemble
into the casein micelles of milk, which aggregate to form the curd of
cheese; proteins and ribonucleic acids assemble into ribosomes, the
machinery for building proteins; lipids and proteins assemble into cell
membranes, the external barriers and internal surfaces of cells; proteins
and DNA wind up into chromosomes, the carriers of the genetic code; and so
on.
Consequently, much effort in biophysics is directed to determining the
structure of specific biological molecules and of the larger structures into
which they assemble. Some of this effort involves inventing new methods and
in building new instruments for viewing these structures. Many of the
exciting new developments in biological microscopy, described here under
Resources in Biophysics, are part of this effort.
What
Does Biophysics Study?
The
biological questions with which biophysics is concerned are as diverse
as the organisms of biology:
-
How do
linear polymers of only 20 different amino acids fold into proteins with
precise three-dimensional structures and specific biological functions?
-
How does
a single enormously long DNA molecule untwist and exactly replicate itself
during cell division or direct the production of proteins?
-
How are
sound waves, or photons, or odors, or flavors, or touches, detected by
a sense organ and converted into electrical impulses that provide the brain
with information about the external world?
-
How does
a muscle cell convert the chemical energy of ATP hydrolysis into mechanical
force and movement?
-
How does
the cell membrane, a lipid barrier impermeable to water-soluble molecules,
selectively transport such molecules through its non-polar interior?
Biophysics
seeks to answer these questions using an eclectic approach. The specific
molecules involved in a biological process are identified using the techniques
of chemical and biochemical analysis. Their molecular structures
and interactions are determined using the spectroscopic techniques of physics
and chemistry. And the relationship between biological function and
molecular structure is investigated using highly precise and exquisitely
sensitive physical instruments and techniques that are able to monitor
the properties or the movement of specific groups of molecules, or in exciting
new developments, are able to view and manipulate single molecules and
to measure their behavior.
Biophysics
explains biological functions in terms of molecular mechanisms: precise
physical descriptions of how individual molecules work together like tiny
machines to produce specific biological functions. Some of these
biophysical mechanisms, many involving detailed molecular models, are described
in detail under Resources in Biophysics.
Selected Topics in Biophysics
Biophysics
is a diverse and eclectic field, and consequently difficult to categorize.
For the purposes of this summary of educational resources in biophysics,
biophysics is divided into three parts or topic areas: molecular structures,
biophysical techniques, and biological mechanisms. Each topic area is defined
here and an attempt is made to indicate how these areas are interrelated
within the field of biophysics. An annotated list of specific resources,
available as text files or web sites, for each topic area is then provided
on subsequent pages.
Every
effort is made to ensure that links to sites maintained by other institutions
or individuals are active, educational, and accurate. If you find otherwise,
please contact the Society at society@biophysics.org
or at
301-634-7114.
Molecular
Structures
Biophysics explains the biological
functions of cells, tissues, and organisms in terms of the structure and
behavior of biological molecules. Genes, the basic elements of biological
information, reflect the molecular structures of the enormously large,
linear DNA (deoxyribonucleic acid) molecules of which they are made.
The behavior of enzymes, hormones, and antibodies reflects the molecular
structures of proteins and the organic chemistry of the functional groups
of the amino acid side chains.& The surface and barrier properties
of biological membranes reflect the ability of lipids to aggregate into
flexible two-dimensional bilayers with hydrophobic cores and polar surfaces.
Information about the molecular structures
and biophysical properties of proteins, nucleic acids (DNA and RNA), lipids,
and carbohydrates is available on the
Select Topics in Biophysics page.
Biophysical
Techniques
The characterization of molecular
structure, the measurement of molecular properties, and the observation
of molecular behavior presents an enormous challenge for biological scientists.
A wide range of biophysical techniques have been developed to study molecules
in crystals, in solution, in cells, and in organisms. These biophysical
techniques provide information about the electronic structure, size, shape,
dynamics, polarity, and modes of interaction of biological molecules. Some
of the most exciting techniques provide images of cells, subcellular structures,
and even individual molecules. It is now possible, for example, to directly
observe the biological behavior and physical properties of single protein
or DNA molecules within a living cell and determine how the behavior of
the single molecule influences the biological function of the organism.
Information about the wide variety
biophysical techniques available to study the structures, properties, and
functions of molecules both in the test tube and in living biological systems
is available on our
Select Topics in Biophysics page.
Biophysical
Mechanisms
Much of the scientific success of
biophysics depends upon its ability to develop detailed physical mechanisms
to explain specific biological processes. The double helical structure
of DNA, for example, provides a framework for an explanation of how genetic
material is replicated and of how genetic mutations arise: specific proteins
mediate the unwinding of the DNA duplex and the assembly of a new strand
based on complementary base pairing of the four DNA bases, guanine with
cytosine and adenine with thymine; mismatch of one of these base pairs
generates a complementary strand with a single base substitution (a mutation).
The value of this, and a variety of other biophysical mechanisms, is unlimited
for human knowledge in general and for biomedical research in particular.
Molecular descriptions
of a variety biological functions are available on our
Select Topics in Biophysics page.
Graduate
Programs in Biophysics
Numerous colleges
and universities throughout the USA and the world support graduate study
in biophysics. Some offer specific graduate degrees in biophysics; others
offer a specialization in biophysics as part of a degree in Chemistry,
Biology, Physics, or other field. Our interactive database allows you to
search for graduate study opportunities in biophysics by geographical location,
by degree offered, and by specific area of research expertise.
