Define concentration gradient
Answers
The formal definition of a concentration gradient is the process of particles, which are sometimes called solutes, moving through a solution or gas from an area with a higher number of particles to an area with a lower number of particles. The areas are typically separated by a membrane. This membrane can be permeable, semi-permeable, or non-permeable. Permeable is defined as a membrane that can be crossed by particles, ions, or water. Semi-permeable means that some particles, ions, or water can cross the membrane. Finally, non-permeable membrane means that no particles, ions, or water can cross the membrane.
An example that might help you understand the different types of membranes would be different types of fences. A wooden log fence would allow many things to pass through - this would be an example of a permeable membrane. A chain link fence would allow some small items to pass through it - this would be like a semi-permeable membrane. A solid plastic fence would not allow items to pass through it at all - this would represent a non-permeable membrane.
ANSWER__ʘ‿ʘ
"Up" or "against" a concentration gradient means from low concentration to high concentration. Moving in this direction requires some sort of energy input, such as active transport using ATP, or an electrical gradient or something else.
MARK BRAINLIEST✓✓