Active transport

In cellular biology, active transport is the movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient. Active transport requires cellular energy to achieve this movement. There are two types of active transport: primary active transport that uses adenosine triphosphate (ATP), and secondary active transport that uses an electrochemical gradient. This process is in contrast to passive transport, which allows molecules or ions to move down their concentration gradient, from an area of high concentration to an area of low concentration, with energy.

Active transport is essential for various physiological processes, such as nutrient uptake, hormone secretion, and nig impulse transmission. For example, the sodium-potassium pump uses ATP to pump sodium ions out of the cell and potassium ions into the cell, maintaining a concentration gradient essential for cellular function. Active transport is highly selective and regulated, with different transporters specific to different molecules or ions. Dysregulation of active transport can lead to various disorders, including cystic fibrosis, caused by a malfunctioning chloride channel, and diabetes, resulting from defects in glucose transport into cells.

Unlike passive transport, which uses the kinetic energy and natural entropy of molecules moving down a gradient, active transport uses cellular energy to move them against a gradient, polar repulsion, or other resistance. Active transport is usually associated with accumulating high concentrations of molecules that the cell needs, such as ions, glucose and amino acids. Examples of active transport include the uptake of glucose in the intestines in humans and the uptake of mineral ions into root hair cells of plants.

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

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.

Rosenberg (1948) formulated the concept of active transport based on energetic considerations, but later it would be redefined.

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

One category of cotransporters that is especially prominent in research regarding diabetes treatment is sodium-glucose cotransporters. These transporters were discovered by scientists at the National Health Institute. These scientists had noticed a discrepancy in the absorption of glucose at different points in the kidney tubule of a rat. The gene was then discovered for intestinal glucose transport protein and linked to these membrane sodium glucose cotransport systems. The first of these membrane transport proteins was named SGLT1 followed by the discovery of SGLT2. Robert Krane also played a prominent role in this field.