Active transport

Active transport is essential for various physiological processes, such as nutrient uptake, hormone secretion, and nerve impulse transmission.

Active transport is usually associated with accumulating high concentrations of molecules that the cell needs, such as ions, glucose and amino acids.

[1] In 1848, the German physiologist Emil du Bois-Reymond suggested the possibility of active transport of substances across membranes.

[2] In 1926, Dennis Robert Hoagland investigated the ability of plants to absorb salts against a concentration gradient and discovered the dependence of nutrient absorption and translocation on metabolic energy using innovative model systems under controlled experimental conditions.

In 1997, Jens Christian Skou, a Danish physician[5] received the Nobel Prize in Chemistry for his research regarding the sodium-potassium pump.

In primary active transport, the proteins involved are pumps that normally use chemical energy in the form of ATP.

Secondary active transport, however, makes use of potential energy, which is usually derived through exploitation of an electrochemical gradient.

Active transport enables these cells to take up salts from this dilute solution against the direction of the concentration gradient.

For example, chloride (Cl−) and nitrate (NO3−) ions exist in the cytosol of plant cells, and need to be transported into the vacuole.

A primary ATPase universal to all animal life is the sodium-potassium pump, which helps to maintain the cell potential.

Hydrolysis of the bound phosphate group and release of hydrogen ion then restores the carrier to its original conformation.

In broad terms, ABC transporters are involved in the import or export of molecules across a cell membrane; yet within the protein family there is an extensive range of function.

In general, volatile compounds may promote the attraction of seed-dispersal organisms and pollinators, as well as aid in defense, signaling, allelopathy, and protection.

To study the protein PhABCG1, transgenic petunia RNA interference lines were created with decreased PhABCG1 expression levels.

Ultimately, PhABCG1 is responsible for the protein-mediated transport of volatile organic compounds, such as benzyl alcohol and methylbenzoate, across the plasma membrane.

Pleiotropic Drug Resistance ABC transporters are hypothesized to be involved in stress response and export antimicrobial metabolites.

This unique ABC transporter is found in Nicotiana tabacum BY2 cells and is expressed in the presence of microbial elicitors.

[20] In August 1960, in Prague, Robert K. Crane presented for the first time his discovery of the sodium-glucose cotransport as the mechanism for intestinal glucose absorption.

An example is the sodium-calcium exchanger or antiporter, which allows three sodium ions into the cell to transport one calcium out.

[24] This antiporter mechanism is important within the membranes of cardiac muscle cells in order to keep the calcium concentration in the cytoplasm low.

Substances that enter the cell via signal mediated electrolysis include proteins, hormones and growth and stabilization factors.