Advertisement Upgrade to remove ads

nuclear envelope

layer of two membranes that surrounds the nucleus of a cell


combination of DNA and protein molecules, in the form of long, thin fibers, making up the genetic material in the nucleus of a eukaryotic cell


condensed threads of genetic material formed from chromatin as a cell prepares to divide


ball-like mass of fibers and granules in a cell nucleus


one of two tiny structures located in the cytoplasm of animal cells near the nuclear envelope

phospholipid bilayer

two-layer "sandwich" of molecules that surrounds a cell


the strength of a solution


the process by which molecules move from an area of higher concentration to an area of lower concentration


When the concentration of a solute is the same throughout a solution


diffusion of molecules through a semipermeable membrane from a place of higher concentration to a place of lower concentration until the concentration on both sides is equal


having a solute concentration equal to that of another solution


having a higher concentration of solute than another solution


having a lower concentration of solute than another solution

facilitated diffusion

pathway provided by transport proteins that helps certain molecules pass through a membrane

active transport

movement of molecules across a membrane requiring energy to be expended by the cell


process of taking material into a cell within vesicles that bud inward from the plasma membrane


the process by which a cell engulfs large particles or whole cells, either as a defense mechanism or as a means to obtain food


process by which a cell takes in liquid from the surrounding environment


process of exporting proteins from a cell by a vesicle fusing with the plasma membrane and spilling the proteins outside the cell

cell specialization

the process in which cells develop in different ways to perform different tasks


cooperating unit of many similar cells that perform a specific function


unit consisting of several tissues that together perform a specific task

organ system

unit of multiple organs that together perform a vital body function


main energy source that cells use for most of their work


straight, hollow tube of proteins that gives rigidity, shape, and organization to a cell


solid rod of protein, thinner than a microtubule, that enables a cell to move or change shape

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again


Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording