At the inner edge of the membrane, next to the cytoplasm, the carrier pump probably dissociates from the transported substance, which is then absorbed by the cytoplasm for metabolic use. Active transport processes in the membrane permit cells to regulate food absorption, hormone and enzyme secretion, and the transfer of genetic material from the cell nucleus to the ribosomes, where protein synthesis occurs. Bioelectrical events also take place in cell membranes. An inflow of sodium ions positively charges the interior of the nerve cell. The Biophysics of Muscle Contraction Muscle contraction is the way the body responds to outside signals and goes about its work.
Contraction is triggered by a nerve impulse that depolarizes the membranes of muscle fibers.
Tiny myofibrils, or muscle strands, in the fibers then slide past each other, shortening the muscle. The energy that fuels the mechanical shortening of the proteins is provided by adenosine triphosphate, a cellular power source. The preceding examples were drawn from specific areas of biophysics research. A broader view shows that the science of biophysics encompasses several levels of biological organization. The molecular level.