In biology, the term is sometimes used in the context of a chemical reaction, in particular to describe the energy source for the chemical synthesis of ATP. In more general terms, however, it is used to characterize the tendency of solutes to simply diffuse across a membrane, a process involving no chemical transformation.
Tags: Electrophysiology, Medical equipment, Medical imaging
Ion channels are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of all living cells (see cell potential) by allowing the flow of ions down their electrochemical gradient.[1] They are present in the membranes that surround all biological cells.
An electrochemical gradient is a spatial variation of both electrical potential and chemical concentration across a membrane. Both components are often due to ion gradients, particularly proton gradients, and the result can be a type of potential energy available for work in a cell. This can be calculated as a thermodynamic measure, termed electrochemical potential, that combines the concepts of energy stored in the form of chemical potential, which accounts for an ion's concentration gradient across a cellular membrane, and electrostatics, which accounts for an ion's tendency to move relative to the membrane potential.
With respect to a cell, organelle, or other subcellular compartment, the tendency of an electrically charged solute, such as a potassium ion, to move across the membrane is decided by the difference in its electrochemical potential on either side of the membrane, which arises from three factors: the difference in the concentration of the solute between the two sides of the membrane the charge or "valence" of the solute molecule the difference in voltage between the two sides of the membrane (i.e. the transmembrane potential). A solute's electrochemical potential difference is zero at its "reversal potential", the transmembrane voltage at which the solute's net
Electrochemical potential is important in electroanalytical chemistry and industrial applications such as batteries and fuel cells. It represents one of the many interchangeable forms of potential energy through which energy may be conserved. In biological processes, the direction an ion moves by diffusion or active transport across a membrane is determined by the electrochemical gradient. In mitochondria and chloroplasts, proton gradients are used to generate a chemiosmotic potential that is also known as a proton motive force. This potential energy is used for the synthesis of ATP by oxidative phosphorylation. An electrochemical gradient has two components. First, the electrical component is caused
Electrochemical potential is important in electroanalytical chemistry and industrial applications such as batteries and fuel cells. It represents one of the many interchangeable forms of potential energy through which energy may be conserved. In biological processes, the direction an ion moves by diffusion or active transport across a membrane is determined by the electrochemical gradient. In mitochondria and chloroplasts, proton gradients are used to generate a chemiosmotic potential that is also known as a proton motive force. This potential energy is used for the synthesis of ATP by oxidative phosphorylation. An electrochemical gradient has two components. First, the electrical component is caused
A biological target is a biopolymer such as a protein or nucleic acid whose activity can be modified by an external stimulus. The definition is context-dependent and can refer to the biological target of a pharmacologically active drug compound, or the receptor target of a hormone (like insulin). The implication is that a molecule is "hit" by a signal and its behavior is thereby changed. Biological targets are most commonly proteins such as enzymes, ion channels, and receptors.
The proton gradient can be used as intermediate energy storage for heat production and flagellar rotation. In addition, it is an interconvertible form of energy in active transport, electron potential generation, NADPH synthesis, and ATP synthesis/hydrolysis. The electrochemical potential difference between the two sides of the membrane in mitochondria, chloroplasts, bacteria, and other membranous compartments that engage in active transport involving proton pumps, is at times called a chemiosmotic potential or proton motive force (see chemiosmosis). In this context, protons are often considered separately using units of either concentration or pH.
The EEG is typically described in terms of (1) rhythmic activity and (2) transients. The rhythmic activity is divided into bands by frequency. To some degree, these frequency bands are a matter of nomenclature (i.e., any rhythmic activity between 8–12 Hz can be described as "alpha"), but these designations arose because rhythmic activity within a certain frequency range was noted to have a certain distribution over the scalp or a certain biological significance. Most of the cerebral signal observed in the scalp EEG falls in the range of 1–20 Hz (activity below or above this range is likely to be
In physiology, transduction is the conversion of a stimulus from one form to another. Transduction in the nervous system typically refers to synaptic events wherein a mechanical/physical/etc stimulus is converted into an action potential which is transmitted along axons towards the central nervous system where it is integrated. For example, in the visual system, sensory cells called rod and cone cells in the retina convert the physical energy of light signals into electrical impulses that travel to the brain. The light causes a conformational change in a protein called rhodopsin. This conformational change sets in motion a series of molecular events that
Electrooculography was used by Robert Zemeckis and Jerome Chen, the visual effects supervisor in the movie Beowulf during the enhanced performance capture to correctly capture and animate the eye movements of the actors. It was an improvement from The Polar Express