Maintaining a stable internal environment

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

a special organic molecule with a polar head and nonpolar tails.

the structure of the cell membrane

a property of cell membranes that allows some substances to pass through, while others cannot

helps move substances across a cell membrane

Transmits messages in and out of cells. They allow communication between cells.

identify the cell to other cells

difference in the amount of a substance from one location to another

when there is an equal amount of molecules on each side of a membrane

Describes the cell membrane as a tapestry of several types of molecules (phospholipids, cholesterols, and proteins) that are constantly moving.

A lipid that forms an essential component of cell membranes that helps keep the phospholipids spaced evenly.

Requires NO energy, Movement of molecules from high to low concentration, Moves with the concentration gradient

Requires energy, Movement of molecules from low to high concentration, Moves against the concentration gradient

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

process of diffusion in which molecules pass across the membrane through cell membrane channels

Diffusion of water through a selectively permeable membrane

A substance that is dissolved in a solution.

A liquid substance capable of dissolving other substances

Solute concentration is less than that inside the cell; cell gains water

Solute concentration is greater than that inside the cell; cell loses water

a solution whose solute concentration is equal to the solute concentration inside a cell

active transport mechanism that helps particles move against the concentration gradient

small membrane sacs that specialize in moving products into, out of, and within a cell

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

release of substances out a cell by the fusion of a vesicle with the membrane.