The spontaneous movement of a substance down its concentration gradient from where it is more concentrated to where it is less concentrated
The diffusion of a substance across a biological membrane, with no expenditure of energy
The diffusion of water across a selectively permeable membrane
The passage of substance through a specific transport protein across a biological membrane down to its concentration gradient
The movement of a substance across a biological membrane against its concentration gradient, aided by specific transport proteins and requiring an input of energy (often as ATP)
A region along which the density of a chemical substance increases or decreases. Cells often maintain concentration gradients of ions across their membranes. When a gradient exists, substances tend to move from where they are more concentrated to where they are less concentrated
Referring to a solution that, when surrounding a cell, will cause the cell to take up water
Referring to a solution that, when surrounding a cell, will cause the cell to lose water
Referring to a solution that, when surrounding a cell, has no effect on the passage of water into or out of the cell
A transport protein in the plasma membrane of some plant or animal cells that facilitates the diffusion of water across the membrane (osmosis)
The movement of materials out of the cytoplasm of a cell by the fusion of vesicles with the plasma membrane
Cellular uptake of molecules or particles via formation of new vesicles from the plasma membrane
Cellular "eating"; a type of endocytosis in which a cell engulfs macromolecules, other cells, or particles into its cytoplasm
Cellular "drinking"; a type of endocytosis in which the cell takes fluid and dissolved solutes into small membraneous vesicles
The movement of specific molecules into a cell by the inward budding of membranous vesicles, which contain proteins with receptor sites specific to the molecules being taken in
A macromolecule, usually a protein, that serves as a biological catalyst, changing the rate of a chemical reaction without being consumed bt the reaction
(1)A specific substance (reactant) on which an enzyme acts. Each enzyme recognizes substrate or substrates of the reaction it catalyzes (2) A surface in or on which an organism
The part of an enzyme molecule where a substrate molecule attaches (by means of weak chemical bonds); typically, a pocket or groove on the enzyme's surface.
The change of shape of an active site of an enzyme, caused by the entry of the substrate, so that it binds more snugly to the substrate
A non protein molecule or ion that is required for the proper functioning of an enzyme
An organic molecule serving as a cofactor. Most vitamins functions as a coenzymes in important metabolic reactions
A substance that reduces the activity of an enzyme by binding to the enzyme's active site in place of the substrate. A competitive inhibitor's structure mimics that of the enzyme's substrate.
A substance that reduces the activity of an enzyme without entering an active site. By binding elsewhere on the enzyme, a noncompetitive inhibitor changes the shape of the enzyme so that the active site no longer effectively catalyzes the conversion of substrate to product
A site that allows molecules to either activate or inhibit (or turn off) enzyme activity
The energy of motion
The energy that matter possesses because of its location or arrangement.
A measure of disorder
An energy-releasing chemical reaction in which the reactants contain more potential energy than the products.
An energy-requiring chemical reaction, which yields more potential energy in the products than the reactants.
A process that requires the presence of oxygen or air as opposed to an anaerobic process that does not require it
Any organism that does not require molecular oxygen for growth
1st Law of Thermodynamics
Energy can neither be created nor destroyed
2nd Law of Thermodynamics
For a spontaneous process, the entropy of the universe increases