Vocabulary

active transport

the movement of material across the cell membrane against its concentration gradient, requiring the cell to expend energy

aquaporin

a transport protein in a cell membrane that allows for osmosis, the diffusion of water across a semipermeable membrane.

carbohydrate

an organic molecule that contains carbon, hydrogen, and oxygen, and provides energy to cells

carrier protein

a protein that physically binds to a molecule and facilitates its transport across the cell membrane's lipid bilayer

cell membrane

the structure that encloses the cell, made of the phospholipid bilayer

cell-surface receptor

a protein embedded in the cell membrane that binds to molecules outside the cell

channel protein

a protein that creates a pathway with a hydrophilic (having a strong affinity to water) interior for ions or polar molecules to pass through

cholesterol

a lipid that forms an essential component of animal cells

diffusion

the random movement of molecules along a concentration gradient from an area of higher concentration to an area of lower concentration

electrochemical gradient

a gradient established by the driving forces of a chemical and electrical change in the cell membrane

endocytosis

a form of bulk transport that moves material into a cell by an infolding of the cell membrane around the material, forming a vesicle (small sac) that moves into the cell

exocytosis

a form of bulk transport used to move material outside the cell by fusion of a vesicle (small sac) with the plasma membrane and release of the contents outside the cell

facilitated diffusion

a form of diffusion that occurs when materials move across the cell membrane with the help of membrane proteins; does not require the cell to expend energy

hydrolysis

the chemical reaction of breaking down a molecule into another form through the addition of water

hydrophilic

having a strong affinity toward water

hydrophobic

having a weak or no affinity to water

hypertonic

a solution in which the concentration of dissolved solutes is greater than that of another solution, or greater than the concentration inside the cell

hypotonic

a solution in which the concentration of dissolved solutes is less than that of another solution, or less than the concentration inside the cell

integral protein

a protein that is embedded within the cell membrane

intracellular receptor

a receptor found within the cell in the cytoplasm or nucleus

isotonic

a solution in which the concentration of dissolved solutes is equal to that of another solution, or equal to the concentration inside the cell

kinetic energy

the energy an object possesses when in motion

ligand

a molecule that binds to receptor proteins

osmolarity

the concentration of solutes (dissolved materials) in a solution

osmosis

the movement of water molecules across a semipermeable membrane from an area of lower concentration of solute to higher concentration of solute

passive transport

the movement of material across the plasma membrane not requiring the cell to expend energy

peripheral protein

a protein that is associated with, but not embedded within, the plasma membrane

phospholipid

a lipid molecule composed of glycerol (a carbon compound) bonded to two fatty acids and a phosphate

phosphorylation

the addition of a phosphate group to a molecule in a chemical reaction

receptor

a protein to which signaling molecules can bind to elicit a physiological response