Answer:
Active transport
The active transport requires an energy expenditure to transport the molecule from one side of the membrane to the other, but the active transport is the only one that can transport molecules against a concentration gradient, just as the diffusion facilitated the active transport is limited by the number of transport proteins present
Explanation:
Two major categories of active, primary and secondary transport are of interest. The primary active transport uses energy (generally obtained from ATP hydrolysis), at the level of the same membrane protein producing a conformational change that results in the transport of a molecule through the protein.
The best known example is the Na + / K + pump. The Na + / K + pump performs a countertransport ("antyport") transports K + into the cell and Na + outside it, at the same time, spending on the ATP process.
The secondary active transport uses energy to establish a gradient across the cell membrane, and then uses that gradient to transport a molecule of interest against its concentration gradient.
An example of this mechanism is as follows: Escherichia coli establishes a proton gradient (H +) between both sides of the membrane using energy to pump protons out of the cell. Then these protons are coupled to lactose (a sugar that serves as a nutrient for the microorganism) at the level of lactose-permease (another transmembrane protein), lactose permease uses the energy of the proton moving in favor of its concentration gradient to transport lactose inside the cell.
This transport coupled in the same direction through the cell membrane is called cotransport ("symport"). Escherichia coli uses this type of mechanism to transport other sugars such as ribose and arabinose, as well as numerous amino acids
