What does cotransport mean?
Cotransport is the process by which a single membrane protein moves two or more different molecules or ions across a cell membrane at the same time, coupling their movements so that the energy stored in the gradient of one substance powers the passage of another. Because the driving gradient is usually built by primary active transport (such as the sodium–potassium pump), cotransport is classified as secondary active transport. The classic example is the sodium–glucose cotransporter of the intestine and kidney, which lets the body absorb glucose even when its concentration inside cells is already high. Closely related terms include symport, for coupled movement in the same direction, and antiport or countertransport, for movement in opposite directions. Cotransport is a technical word found chiefly in physiology, biochemistry, and pharmacology, but it underlies everyday processes from digesting lunch to reabsorbing nutrients, making it a rewarding term for anyone curious about how living cells manage traffic across their boundaries.
nounThe transport of two or more different molecules or ions across a biological membrane by a single transport protein, in which the movement of one substance is coupled to the movement of another. It is a form of secondary active transport, typically driven by the concentration gradient of an ion such as sodium or a proton.
- The coupled movement of two or more substances across a cell membrane via a shared transport protein, driven by the electrochemical gradient of one of them (secondary active transport).
"Glucose enters intestinal cells through cotransport with sodium ions."
"Sodium–glucose cotransport in the small intestine allows the body to absorb sugars even against their concentration gradient."
"Many antibiotics exploit bacterial proton cotransport systems to enter cells."
Rarely used in the plural; the uncountable singular is standard, though plural forms appear occasionally when referring to multiple distinct cotransport mechanisms.
"Different cotransports operate on either side of the intestinal cell membrane."
Every sip of water you absorb relies on cotransport — your cells smuggle nutrients across membranes by hitching them to the flow of sodium ions.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cotransport
Cotransport is a modern scientific coinage formed from the Greek-derived prefix co- ('together') and the Latin-rooted word transport, from trans- ('across') plus portare ('to carry'). The compound arose in twentieth-century biochemistry, when researchers discovered that nutrient uptake in cells depended on the simultaneous movement of ions such as sodium. Its relatives — transport, portable, export, and import — all descend from the same Latin verb portare.
How cotransport is actually used
A technical term used almost exclusively in biochemistry, physiology, and cell biology; it is rare in general prose. In strict usage, some authors reserve 'cotransport' for same-direction movement (symport) and use 'countertransport' for opposite-direction movement (antiport), while others apply 'cotransport' to any coupled transport. The verb form 'cotransported' appears mainly as a participle.
Easily confused with cotransport
Countertransport (antiport) moves two substances across the membrane in opposite directions, whereas cotransport typically refers to their movement in the same direction.