What is secondary active transport?

[sameeralord]

Hello,

Ok I researched it but I don't understand. What I understand is that when one molecule normally diffuses(high to low) another molecule from a (low to high gradient) attaches to the carrier protein. How does this molecule attach without ATP? I don't get it. Any help would be appreciated. I'm talking about membrane transport of course!

 

[Smachine]

Im not sure which part of the mechanism are you not understanding, but the general idea is quit simple. ATP energy is spent to create concentration and possible also electrical gradient for one substance across cell membrane and the other substance is transported together with the first substance by using this stored energy. Good example is SGLT1 glucose transporter protein, that moves Na⁺ ions in the direction of their electrochemical gradient and glucose molecules against their concentration gradient. Energy for this still comes from ATP, but is stored as electrochemical gradient and then its used for transport purpose.

 

[quicknote]

Secondary active transport is a type of transport mechanism in which a molecule is transported across a cell membrane against its concentration gradient, using the energy stored in the electrochemical gradient of another molecule. This type of transport does not directly require the use of ATP, but rather uses the energy from the electrochemical gradient of the other molecule to drive the transport.

In secondary active transport, the movement of one molecule down its concentration gradient provides the energy needed to transport another molecule against its concentration gradient. This is achieved through the use of carrier proteins, which bind to both molecules and facilitate their movement across the membrane.

To answer your question about how the molecule attaches to the carrier protein without ATP, it is important to understand that carrier proteins have specific binding sites for the molecules they transport. When the molecule with a higher concentration outside the cell binds to the carrier protein, it causes a conformational change in the protein that allows the molecule with a lower concentration inside the cell to bind as well. This binding process releases the energy needed to transport the molecule against its concentration gradient.

I hope this explanation helps clarify the concept of secondary active transport for you. If you have any further questions, please don't hesitate to reach out.