The correct answer is A. Active Transport.
Active transport is the movement of molecules across a cell membrane against a concentration gradient, using energy from ATP. This is in contrast to passive transport, which is the movement of molecules down a concentration gradient, without the use of energy.
Active transport is necessary for cells to maintain homeostasis, or a stable internal environment. For example, cells use active transport to move sodium ions out of the cell and potassium ions into the cell. This creates a difference in electrical charge across the cell membrane, which is important for nerve cell function.
Active transport is also used by cells to absorb nutrients from the environment. For example, cells use active transport to take up glucose from the bloodstream.
Passive transport is the movement of molecules across a cell membrane down a concentration gradient. This means that molecules move from an area where they are in high concentration to an area where they are in low concentration. No energy is required for passive transport.
There are two types of passive transport: diffusion and osmosis. Diffusion is the movement of molecules from an area of high concentration to an area of low concentration. Osmosis is the movement of water across a semipermeable membrane from an area of high water concentration to an area of low water concentration.
Endocytosis is the process by which cells take in large molecules or particles. This process involves the formation of a vesicle around the molecule or particle, which is then taken into the cell.
Fractionation is the process of separating different components of a mixture. This can be done using a variety of methods, such as centrifugation, filtration, and distillation.
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