Chapter 6 - Energy & Metabolism Flashcards
Amount of work a thermodynamic system can perform. The internal energy of a system minus the amount of energy that cannot be used to perform work.
Free energy
A chemical reaction in which the standard change in free energy is positive, and energy is absorbed.
Endergonic reaction
A reaction where energy is released. Because the reactants lose energy (G decreases), Gibbs free energy (ΔG) is negative under constant temperature and pressure. These reactions usually do not require energy to proceed, and therefore occur spontaneously.
Exergonic reaction
Releases free energy (usually as heat) and moves to a lower, more thermodynamically stable energy state. When ΔG is negative, a process or chemical reaction proceeds spontaneously in the forward direction.
Spontaneous reaction
Equilibrium Constant
Chemical reactions are reversible, therefore an exergonic reaction moving in a forward direction will be endergonic in reverse direction. For each reaction, an equilbrium exists. This numerical value is the EC.
Extra energy needed to destabilized existing chemical bonds and initiate a chemical reaction.
Activation evergy
The substrates that influence chemical bonds in a way that lowers the activation energy needed to initiate a reaction.
Catalyst
ATP Composition
Adonisine triphosphate; composed of three smaller components: a five-carbon sugar (ribose), an organic molecule composed of two carbon-nitrogen rings (adenine), and a chain of three phosphates (triphosphate). Stores energy in triphosphates
ATP
Stores energy in triphosphate group. When unstable bonds are broken by hydrolysis, energy is released.
ADP
When outermost high energy phosphate bond is hydrolyzed, phosphate group is cleaved off the end and becomes ADP (adonisine diphosphate).
Protein that is capable of speeding up the specific chemical reactions by lowering the required activation energy.
Enzyme
Complex formed when an enzyme binds with its substrate. Often has an altered configuration compared with non-bound enzyme.
Enzyme substrate complex
Foundation to which an organism is attached.
Substrate
Region of an enzyme surface to which a specific set of substrates binds, lowering the activation energy required for a particular chemical reaction and so facilitating it.
Active site
When an enzyme binds to the appropriate substrate, subtle changes in the active site occur. Enhances catalysis, as the enzyme converts substrate to product.
Induced fit
Assembly consisting of several enzymes catalyzing different steps in a sequence of reactions. Close proximity speeds process and makes more efficient.
Multienzyme complex
RNA molecule that can behave as an enzyme, sometimes catalyzing its own assembly; rRNA also acts as one in polymerization of amino acids to form protein.
ribozyme
Substance that binds to an enzyme and decreases its activity.
Inhibitor
Compete with the substrate for the same active site, occupying the active site and preventing substrates from biding.
Competitive inhibitors
Bind to the enzyme in a location other that the active site, changing the shape of the enzyme and making it unable to bind to a substrate.
Noncompetitive inhibitors
Enzymes that can exist in either active or inactive conformation.
Allosteric enzyme
Where noncompetative inhibitors bind to a specific portion of the enzyme.
Allosteric site
Substance that binds to an allosteric site and reduces enzyme activity.
Allosteric inhibitor
Binds to allosteric sites to keep an enzyme in its active configuration, thereby increasing enzyme activity.
Allosteric activator
