What is included in a cell's metabolism? What does it mean to move down a concentration gradient?

2 other questions- What does it mean to move something against its concentration gradient? How does the cell membrane protect the cell?What is included in a cell's metabolism? What does it mean to move down a concentration gradient?
';Metabolism is the set of chemical reactions that occur in living organisms in order to maintain life.';





A concentration gradient is when there is a difference in the amount of a solute in one area compared to another. In moving down its gradient, a molecule would move from an area of high concentration to an area of low concentration. An example is when you put sugar in your tea or coffee. When you first put it in, it is mostly located on the bottom of the cup. However, molecules dissolve in the hot liquid, and move throughout the cup, until after a while, the whole cup tastes sweet.





In order to move something against a concentration gradient, it would have to move from an area of low concentration to an area of high concentration. It would not ordinarily do this naturally; in order to accomplish it, a cell must expend energy, usually in the form of ATP.





The cell membrane is semi-permeable, meaning that some things can move through it, while others cannot. What can be moved through it is regulated by the membrane. It protects the cell by maintaining its high concentration of necessary nutrients, ions, etc., partially by diffusion (things moving naturally down their concentration gradient), partially by active transport (using ATP to move things against their concentration gradient.