transport protein
an embedded protein that helps a certain type of substance to cross the membrane
diffusion
the movement of small particles from a region of high concentration to low concentration.
passive transport
the diffusion of a substance across the cell membrane without the need of energy
osmosis
the diffusion of water across a membrane
facilitated diffusion
the passage of molecules across a membrane with the help of specific transport proteins, requiring no energy.
active transport
the movement of a substance across a cell membrane against its concentration gradient, requires ATP
phospholipid bilayer
a double layer of phospholipid molecules that form membranes in cells
hydrophobic
the tail of a phospholipid molecule that is repelled by water
hydrophilic
the head of a phospholipid molecule that is attracted to water
ATP
the molecule that provides energy for cellular processes by breaking a bond
cholesterol
molecule important in cell membranes because it allows it to remain fluid
hypotonic solution
contains less solute concentration than the cell; water will tend to enter the cell and it will swell
hypertonic solution
when a cell is placed in a solution and the concentration of the solute outside of the cell is higher than it is inside
isotonic solution
A solution in which the concentration of solutes is equal to that of inside the cell
solute
A substance that is dissolved in a solution.
solvent
In a solution, the substance in which the solute dissolves.
Cell Membrane
Layer around every cell that separates it from the outside environment;it controls what can enter and leave the cell.
Homeostasis
Maintaining balance inside the cell