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Chapter 8
Introduction to Metabolism
33
Biology
12th Grade
01/05/2013

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Term
Metabolism
Definition
The totality of an organism's chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism. 
Term
Metabolic Pathway
Definition
A series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule to simpler molecules (catabolic pathway). 
Term
Catabolic Pathway 
Definition
A metabolic pathway that releases energy by breaking down complex molecules to simpler molecules. 
Term
Anabolic Pathways
Definition
A metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules. 
Term
Bioenergetics 
Definition
The study of how energy flows through organisms. 
Term
Energy
Definition
The capacity to cause change, especially to do work (to move matter against an opposing force). 
Term
Kinetic Energy
Definition
The energy associated with the relative motion of objects. Moving matter can perform work by imparting motion to other matter. 
Term
Heat
Definition
The total amount of kinetic energy due to the random motion of atoms or molecules in a body of matter; also called thermal energy. Heat is energy in its most random form. 
Term
Potential Energy
Definition
The energy that matter possesses as a result of its location or spatial arrangement (structure). 
Term
Chemical Energy
Definition
Energy available in molecules for release in a chemical reaction; a form of potential energy. 
Term
Thermodynamics
Definition
The study of energy transformations that occur in a collection of matter. 
Term
First Law of Thermodynamics
Definition
The principle of conservation of energy: Energy can be transferred and trnsformed, but it cannot be created or destroyed. 
Term
Entropy
Definition
A measure of disorder, or randomness. 
Term
Second Law of Thermodynamics
Definition
The principle stating that every energy transfer or transformation increases the entropy of the universe. Usable forms of energy are at least partly converted to heat. 
Term
Spontaneous Process
Definition
A process that occurs without an overall input of energy; a process that is energetically favorable.
Term
Free Energy
Definition
The portion of a biological system's energy that can perform work when the temperature and pressure are uniform throughout the system. The change in free energy of a system (delta G) is calculated by the equation delta G = delta H - TdeltaS, where delta H is the change in enthalpy (in biological systems, equivalent to total energy), T is the absolute temperature, and delta S is the change in entropy. 
Term
Exergonic Reaction
Definition
A spontaneous chemical reaction, in which there is a net release of free energy. 
Term
Endergonic Reaction
Definition
A nonspontaneous chemical reaction, in which free energy is absorbed from the surroundings. 
Term
Energy Coupling 
Definition
In cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction. 
Term
ATP (Adenosine Triphosphate)
Definition
An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells. 
Term
Phosphorylated Intermediate
Definition
A molecule (often a reactant) with a phosphate group convalently bound to it, making it more reactive (less stable) than the unphosphorylated molecule. 
Term
Activation Energy
Definition
The amount of energy that reactants must absorb before a chemical reaction will start; also called free energy of activation. 
Term
Substrate
Definition
The reactant on which an enzyme works. 
Term
Enzyme-Substrate Complex
Definition
A temporary complex formed when an enzyme binds to its substrate molecule(s). 
Term
Active Site
Definition
The specific region of an enzyme that binds to the substrate and that forms the pocket in which catalysis occurs. 
Term
Induced Fit 
Definition
Caused by entry of the substrate, the change in shape of the active site of an enzyme so that it binds more snugly to the substrate. 
Term
Cofactor
Definition
Any nonprotein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can be permanently bound to the active site or may bind loosely annd reversibly along with the substrate, during catalysis. 
Term
Coenzyme 
Definition
An organic molecule serving as a cofactor. Most vitamins function as coenzymes in metabolic reactions. 
Term
Competetive Inhibitors
Definition
A substance that reduces the activity of an enzyme by entering  the active site in place of the substrate, whose structure it mimics. 
Term
Noncompetitive Inhibitor
Definition
A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing the enzyme's shape so that the active site no longer effectively catalyzes the conversion of substrate to product. 
Term
Allosteric Regulation
Definition
The binding of a regulatory molecule to a protein at one site that affects the function of a protein at a different site. 
Term
Cooperativity
Definition
A kind of allosteric regulation whereby a shape change in one subunit of a protein caused by substrate binding is transmitted to all the other subunits, facilitating binding of additional substrate molecules to those subunits. 
Term
Feedback Inhibition
Definition
A method of metabolic control in which the end product of a metabolic pathways acts as an inhibitor of an enzyme within that pathway. 
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