Active and Passive Transport

Osmosis

Diffusion of water through a selectively permeable membrane

semipermeable

some substances can pass across and others cannot

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

High Concentration

when molecules are more crowded in one area compared to another

low concentration

when molecules are less crowded in one area compared to another

Cell Membrane

thin, flexible layer around a cell; regulates what enters and leaves the cell

Passive Transport

the movement of substances across a cell membrane without the use of energy by the cell

Three types of Passive Transport

osmosis, diffusion, facilitated diffusion

Facilitated diffusion

Movement of specific molecules across cell membranes through protein channels

Active Transport

Energy-requiring process that moves material across a cell membrane against a concentration difference (low to high concentration)

osmosis

When water molecules move across a membrane from a high concentration to a low concentration.

diffusion

molecules crossing the membrane from a high concentration to a low concentration

Equilibrium

when the concentration of the solute is the same on both sides of the membrane

Hypertonic

Having a higher concentration of solute than another solution.

Hypotonic

Having a lower concentration of solute than another solution

Isotonic

when the concentration of two solutions is the same

Endocytosis

process by which a cell takes material into the cell by infolding of the cell membrane

Phagocytosis

A type of endocytosis in which a cell engulfs large particles or whole cells

Pinocytosis

A type of endocytosis in which the cell ingests extracellular fluid (or small particles) and its dissolved solutes.

Exocytosis

a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.

sodium-potassium pump

a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell

receptor-mediated endocytosis

The bulk transport of substances into a cell, that are only allowed into the cell if the substance can fit into the cell's receptors.