the outer edges of a cell, also called the plasma membrane, that is thin and flexible. it regulates what enters and leaves the cell and also provides protection and support.
a double-layered sheet that makes up the cell membrane
fluid mosaic model
so many kinds of molecules are in cell membranes that they make up a fluid mosaic of proteins, lipids and carbohydrates
the main function of the cell wall is to provide support and protection for the cell
diffusion through cell membrane
the movement of dissolved molecules from the liquid on one side of the membrane to the liquid on the other side
the mass of solute in a given volume of solution, or mass/volume
diffusion in a solution
the particles in a solution tend to move from an area where they are more concentrated to an area where they are less concentrated
when particles are equally distributed throughout a solution
Because diffusion depends upon random particle movements, substances diffuse across membranes without requiring the cell to use energy.
the diffusion of water through a selectively permeable membrane
"same strength", when the fluid on one side of a cell wall and the other side is equally mixed
"above strength" more concentrated on one side than the other
"below strength" less concentrated on one side than the other (see photo on page 186)
occurs on the hypertonic side of a selectively permeable membrane. If it builds too much the cell will explode.
molecules that cannot pass through the cell wall on their own move through protein channels instead. Glucose moves through blood in this way.
requires energy o move moelcules against a concentration difference. small "pumps" are found in the membrane itself
process of taking material into the cell by infoldings, or pockets of the cell membrane
extensions of cytoplasm surround a particle and package it in a food vacuole. The cell then engulfs it. (active transport)
cells that take up liquid from the surrounding environment
the membrane of a vacuole surrounding the material fuses with the cell membrane, forcing the contents out of the cell - for example, moving water by means of a contractile vacuole