Chapter 5 Energy Flow in the Life of a Cell Flashcards
Activation Energy
In a chemical reaction, the energy needed to force the electron shells of reactants together, before the formation of products.
Active Site
The region of an enzyme molecule that binds substrates and performs the catalytic function of the enzyme.
Adenosine Diphosphate (ADP)
A molecule composed of the sugar ribose, the base adenine, and two phosphate groups; a component of ATP.
Adenosine Triphosphate (ATP)
A molecule composed of the sugar ribose, the base adenine, and three phosphate groupsl thge major energy carrier in cells. The last two phosphate groups are attached by “high-energy” bonds.
Allosteric Regulation
The process by which enzyme action is enhanced or inhibited by small organic molecules that act as regulators by binding to the enzyme and altering its active site.
Catalyst
A substance that speeds up a chemical reaction without itself being permanently changed in the process; lowers the activation energy of reaction.
Chemical Reaction
The process that forms and breaks chemical bonds that hold atoms together.
Competitive Inhibition
The prcoess by which two or more molecules that are somewhat similar in structure compete for the active site of an enzyme.
Coupled Reaction
A pair of reaction, one exergonic and one endergonic, that are linked together such that energy proiduced by the exergonic reaction proivides the energy needed to drive the endergonic reaction.
Electron Carrier
A molecule that can reversibly gain or lose electrons. Electron carriers generally accept high-energy electons produced during an exergonic reaction and donate the electrons to acceptor molecules that use the energy to drive endergonic reactions.
Endergonic Reaction
A chemical reaction that requires an input of energy to proceed.
Energy
The capacity to do work.
Energy-Carrier Molecule
A molecule that stores energy in “high-energy” chemical bonds and released the energy to drive coupled endothermic reactions. In cells, adenosine triphosphate (ATP) is the most common energy-carrier molecule.
Entropy
A measure of the amount of randomness and disorder in a system.
Enzyme
A protein catalyst that speeds up the rate of specific biological reactions.
Exergonic Reaction
A chemical reaction that liberates energy (either as heat or in the form of increased entropy)
First Law of Thermodynamics
The principle of physics that states that within any isolated system, energy can be neither created nor destroyed but can be converted from one form to another.
Kinetic Energy
The energy of movement; includes light, heat, mechanical movement, and electricity.
Metabolic Pathway
A sequence of chemical reactions within a cell, in which the products of one reaction are the reactants for the next reaction.
Metabolism
The sum of all chemical reactions that occu within a single cell or within all of the cells of a multicellular organism.
Potential Energy
“Stored” energy, normally chemical energy or energy of position within a gravitational field.
Product
A atom or molecule that is formed from reactants in a chemical reaction.
Reactant
An atom or molecule that is used up in a chemical reaction to form a product.
Second Law of Thermodynamics
The principle that any change in an isolated system causes the quantity of concentrated, useful energy to decrease and the amount of randomness and disorder (entropy) to increase.
Substrate
The atoms or molecules that are the reactants for an enzyme-catalyzed chemical reaction.
