Chapter 5 Flashcards
diffusion
The spontanepus tendency of a substance to move down its concentration gradient from where it is more concentrated to where it is less concentrated.
kinetic energy
The energy of motion; the energy of a mass of matter that is moving. Moving matter does work by imparting motion to other matter.
competitive inhibitor
A substance that reduces the activity of an enzyme by binding to the enzyme’s active site in a place of the substrate. A competitive inhibitor’s structure mimics that of the enzyme’s substrate.
hypertonic
Referring to a solution that, when surrounding a cell, will cause the cell to lose water
noncompetitive inhibitor
A substance that impedes 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 functions.
coenzyme
An organic molecule serving as a cofactor. Most vitamins function as coenzymes in important metabolic reactions.
substrate
1) A specific substance (reactant) on which an enzyme acts. Each enzyme recognizes only the specific substrate or substrates of the reaction it catalyzes. 2) A surface in or on which an organism lives.
metabolism
the totality of an organism’s chemical reactions.
chemical energy
Energy available in molecules for release in a chemical reaction; a form of potential energy.
entropy
A measure of disorder. One form of disorder is heat, which is random molecular motion.
heat
Thermal energy; the amount of energy associated with the movement of the atoms and molecules in a body of matter. Heat is energy in its most random form.
selective permeability
A property of biological membranes that allows some substances to cross more easily that others and blocks the passage of other substances altogether.
tonicity
The ability of a solution surrounding a cell to cause that cell to gain or lose water.
isotonic solution
a solution having the same solute concentration as another solution, thus having no effect on passage of water in or out of the cell.
first law of thermodynamics
The principle of conversation of energy. Energy can be transferred and transformed, but it cannot be created or destroyed.
feedback inhibition
A method of metabolic control in which a product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.
second law of thermodynamics
The principle whereby every energy conversion reduces the order of the universe, increasing its entropy. Ordered forms if energy are at least partly converted to heat.
potential energy
The energy that matter possesses because of its location or arrangement. Water behind a dam and chemical bonds possess potential energy.
pinocytosis
Cellular “drinking”; a type of endocytosis in which the cell takes fluid and dissolved solutes into small membranous vesicles.
cellular respiration
The aerobic harvesting of energy from food molecules; the energy-releasing chemical breakdown of food molecules, such as glucose, and the storage of potential energy in a form that cells can use to perform work; involves glycolysis, the citric acid cycle, and oxidative phosphorylation (the electron transport chain and chemiosmosis).
enzyme
A protein (or RNA molecule) that serves as a biological catalyst, changing the rate of a chemical reaction without itself being changed into a different molecule in the process.
hypotonic
Referring to a solution that , when surrounding a cell, will cause the cell to take up water.
phagocytosis
Cellular “eating”; a type of endocytosis whereby a cell engulfs macromolecules, other cells, or particles into its cytoplasm.
energy coupling
In cellular metabolism, the use of energy released from an exergonic reaction to drive an enderonic reaction.
andenosine triphosphate (ATP)
Main energy source for cells.
active transport
The movement of a substance across a biological membrane against its concentration gradient, aided by specific transport proteins and requiring input of energy (often as ATP)
facilitated diffusion
The passage of a substance through a specific transport protein across a biological membrane down its concentration gradient.
energy
The capacity to perform work, or to rearrange matter.
exocytosis
The movement of materials out of the cytoplasm of a cell by the fusion of vesicles with the plasma membrane.
thermodynamics
The study of energy transformation that occurs in a collection of matter. See first law of thermodynamics; second law of thermodynamics.
passive transport
The diffusion of a substance across a biological membrane, without any input of energy.
receptor-mediated endocytosis
the movement of specific molecules into a cell by the inward budding of membranous vesicles. The vesicles contain proteins with receptor sites specific to the molecules being taken in.
active site
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.
osmosis
The diffusion of water across a selectively permeable membrane.
concentration gradient
An increase or decrease in the density of a chemical substance in an area. 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.
metabolic pathway
A series of chemical reactions that either builds a complex molecule or breaks down a complex molecule into simpler compounds.
endergonic reaction
An energy-requiring chemical reaction which yields products with more potential energy than the reactants. The amount of energy store in the product equals the difference between the potential energy in the reactants and the in the products.
osmoregulation
Method by which organisms regulate solute concentrations and balance the gain and loss of water.
phosphorylation
The transfer of a phosphate group, usually from ATP, to a molecule. Nearly all cellular work depends on ATP energizing other molecules by phosphorylation.
aquaporin
A transport protein in the plasma membrane of some plant or animal cells that facilitates the diffusion of water across the membrane (osmosis).
exergonic reaction
An energy-releasing chemical reaction in which the reactants contain more potential energy than the products. The reaction releases an amount of energy equal to the difference in potential energy between the reactants and the products.
fluid mosaic
A description of membrane structure, deicing a cellular membrane as a mosaic of diverse protein molecules embedded in a fluid bilayer made of phospholipid molecules.
endocytosis
Cellular uptake of molecules or particles via formation of new vesicles from the plasma membrane.
induced fit
the change in shape of the active site of an enzyme, induced by entry of the substrate so that it binds more snugly to the substrate.
cofactor
A nonprotein molecule or ion that is required for the proper functioning of an enzyme.
