What is Biophysics?

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Excerpt taken from
The Biophysical Society:

Biophysics is that branch of knowledge that applies the principles of physics and chemistry and the methods of mathematical analysis and computer modeling to biological systems, with the ultimate goal of understanding at a fundamental level the structure, dynamics, interactions, and ultimately the function of biological systems. Biophysics seeks to explain biological function in terms of the physical properties of specific molecules. The size of these molecules varies 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 20 nm wide). These 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. Thus, 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; and proteins and DNA wind up into chromosomes, the carriers of the genetic code.

Much effort in biophysics is directed to determining the structure and dynamics of specific biological molecules and of the larger architecture into which they assemble. Some of this effort involves inventing new methods and building new instruments for viewing these dynamic structures in action. In addition, biophysicists are increasingly concerned with the mechanical properties of biological systems, on length scales from nanometers to meters.

Biophysics is relevant to medicine, and many biophysicists direct their investigations towards biomolecules that play a key role in disease. At Michigan, examples include Alzheimer’s disease, ALS (“Lou Gehrig’s disease”), HIV, diabetes, breast cancer, and multiple sclerosis. Consequently, although the central focus of Biophysics is on basic science rather than medical applications, many of our biophysicists have close interactions with medical school faculty, and many hold appointments in the medical school.

The biological questions of interest to biophysics 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?
  • How does RNA fold into complex 3-D structures and carry out highly sophisticated transactions when it is composed of four chemically-similar nucleotides?
  • How are sound waves, or photons, or odors, or flavors, or touches, detected by a sensory 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 a highly interdisciplinary approach that combines chemical and biochemical analysis for identifying molecules and spectroscopic techniques and computational methods to examine relationships between their physical properties and biological function. In so doing, Biophysics explains biological functions in terms of molecular mechanisms: precise physical descriptions of how individual molecules work together like tiny “nanomachines” to produce specific biological functions.