facilitated diffusion.
A transport protein, a large polar molecule, a semi-permeable membrane and a concentration gradient.
Two major means of active membrane transport are primary active transport, which directly uses energy in the form of ATP to transport molecules against their concentration gradient, and secondary active transport, which uses the energy stored in the electrochemical gradient of one molecule to drive the transport of another molecule against its gradient.
The molecule or ion cross the membrane with the energy provided by ATP as it moves up the concentration gradient.
Active transport is the process that requires cellular energy to move a substance against its concentration gradient. This process uses ATP to pump molecules across the cell membrane, creating a concentration gradient where the molecule is more concentrated on one side of the membrane than the other.
In active transport the ATP is used to pump molecules up the concentration gradient. Transport of molecules occurs from a low concentration of solute to high concentration of solute and requires cellular energy. While passive transport involves carriers, channels, or direct diffusion through a membrane.
What is the situation? Provided a concentration gradient and a molecule that passes through a membrane, diffusion will happen. Generally small and nonpolar molecules will pass through a membrane down a concentration gradient. That doesn't answer your question but it may be the answer your looking for.
Ion moving against a concentration gradient
Active transport requires energy to move a molecule.
ATP (adenosine triphosphate) is the organic molecule needed for active transport. It provides the energy required to pump molecules against their concentration gradient across a cell membrane.
determined by the concentration gradient and electrical gradient across the membrane. If the net movement of ions or molecules is down their concentration gradient and towards the opposite electrical charge, they will move across the membrane.
Active transport utilizes energy, such as ATP, to move molecules against their concentration gradient across the cell membrane. Facilitated transport, on the other hand, moves molecules down their concentration gradient with the help of transport proteins but does not require energy input.
The random movement of molecules and ions down their concentration gradient (meaning from an area of high concentration to an area of low concentration) is called simple diffusion. Simple diffusion is related to the magnitude of driving force, permeability of the membrane, and surface area.