Question

which is the best definition of active transport?movement of water across a semi permeable membrane from an area of higher water concentration to an area of lower water concentrationmovement of molecules from an area of their lower concentration to an area of their higher concentrationmovement of molecules from an area of their higher concentration to an area of their lower concentrationmovement of a substance against its concentration through the release of energy from atpmovement of water across a semi permeable membrane from an area of lower water concentration to an area of higher water concentration

Answer 1

The best definition of active transport is the movement of molecules or ions across a cell membrane against their concentration gradient, requiring the expenditure of energy, usually in the form of ATP (adenosine triphosphate). This process enables cells to transport substances from an area of lower concentration to an area of higher concentration, thereby maintaining or establishing concentration gradients necessary for various cellular functions. Unlike passive transport, which relies on the natural flow of molecules from higher to lower concentration, active transport actively pumps molecules or ions across the membrane, allowing the cell to control the movement of specific substances in and out of the cell.

Answer 2

Active transport is the energy-dependent movement of substances against their concentration gradient, from an area of lower concentration to one of higher concentration, requiring ATP.

Step-by-step explanation:

The best definition of active transport is the movement of molecules from an area of their lower concentration to an area of their higher concentration. This process is facilitated by membrane proteins and requires energy, usually in the form of adenosine triphosphate (ATP). Unlike passive transport where substances move along their concentration gradient without the use of energy, during active transport, substances move against their gradient. This is essential for maintaining concentrations of various substances inside a cell, such as ions. An example of active transport is the sodium-potassium pump which actively pumps sodium out of cells and potassium into cells.

It is different from passive transport, which does not require energy and moves molecules from an area of higher concentration to an area of lower concentration. An example of active transport is the sodium-potassium pump, which moves sodium out of cells and potassium into cells, against their concentration gradients.