49 terms

BIO201 - Chapter 3

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Activation energy
The minimal kinetic energy needed for a reactant to undergo a chemical reaction.
Active site
The part of an enzyme molecule that is directly involved in binding the substrate.
Allosteric modulation
Modification of the activity of an enzyme through interaction with a compound that binds to a site (i.e., allosteric site) other than the active site.
Anabolic pathway
A metabolic pathway resulting in the synthesis of relatively complex products.
Bioenergetics
The study of the various types of energy transformations that occur in living organisms.
Catabolic pathway
A metabolic pathway in which relatively complex molecules are broken down into simpler products.
Coenzyme
An organic, nonprotein component of an enzyme.
Cofactor
The nonprotein component of an enzyme, it can be either inorganic or organic.
Competitive inhibitor
An enzyme inhibitor that competes with substrate molecules for access to the active site.
Dehydrogenase
An enzyme that catalyzes a redox reaction by removing a hydrogen atom from one reactant.
Endergonic reactions
Reactions that are thermodynamically unfavorable and cannot occur spontaneously, possessing a +ΔG value.
Endothermic reactions
Those gaining heat under conditions of constant pressure and volume.
Energy
The capacity to do work, it exists in two forms: potential and kinetic.
Entropy (S)
A measure of the relative disorder of the system or universe associated with random movements of matter; because all movements cease at absolute zero (0 K), entropy is zero only at that temperature.
Enzyme inhibitor
Any molecule that can bind to an enzyme and decrease its activity, classified as noncompetitive or competitive based on the nature of the interaction with the enzyme.
Enzymes
The vitally important protein catalysts of cellular reactions.
Enzyme—substrate complex
The physical association between an enzyme and its substrate(s), during which catalysis of the reaction takes place.
Equilibrium constant of a reaction (Keq)
The ratio of product concentrations to reactant concentrations when a reaction is at equilibrium.
Exergonic reactions
Reactions that are thermodynamically favorable, possessing a −ΔG value.
Exothermic reactions
Those releasing heat under conditions of constant pressure and volume.
Feedback inhibition
A mechanism to control metabolic pathways where the end product interacts with an enzyme in the pathway, resulting in inactivation of the enzyme.
Fermentation
An anaerobic metabolic pathway in which pyruvate is converted to another molecule (often lactate or ethanol, depending on the organism) and NAD+ is regenerated for use in glycolysis.
Free energy change (ΔG)
The change during a process in the amount of energy available to do work.
Glycolysis
The first pathway in the catabolism of glucose, it does not require oxygen and results in the formation of pyruvate.
Induced fit
The conformational change in an enzyme after the substrate has been bound that allows the chemical reaction to proceed.
Irreversible inhibitor
An enzyme inhibitor that binds tightly, often covalently, thus inactivating the enzyme molecule permanently.
Kinetic energy
Energy released from a substance through atomic or molecular movements.
Maximal velocity (Vmax)
The highest rate achieved for a given enzymatically catalyzed reaction, it occurs when the enzyme is saturated with substrate.
Metabolic intermediate
A compound produced during one step of a metabolic pathway.
Metabolic pathway
A series of chemical reactions that results in the synthesis of an end product important to cellular function.
Metabolism
The total of the chemical reactions occurring within a cell.
Michaelis constant (KM)
In enzyme kinetics, the value equal to the substrate concentration present when reaction rate is one-half of the maximal velocity.
Noncompetitive inhibitor
An enzyme inhibitor that does not bind at the same site as the substrate, and so the level of inhibition depends only on the concentration of inhibitor.
Oxidation-reduction (redox) reaction
One in which a change in the electronic state of the reactants occurs.
Oxidizing agent
The substance in a redox reaction that becomes reduced, causing the other substance to become oxidized.
Protein kinase
An enzyme that transfers phosphate groups to other proteins, often having the effect of regulating the activity of the other proteins.
Reducing agent
The substance in a redox reaction that becomes oxidized, causing the other substance to become reduced.
Reducing power
The potential in a cell to reduce metabolic intermediates into products, usually measured through the size of the NADPH pool.
Spontaneous reactions
Reactions that are thermodynamically favorable, capable of occurring without any input of external energy.
Standard free-energy change (ΔG°′)
The change in free energy when one mole of each reactant is converted to one mole of each product under defined standard conditions: temperature of 298 K and pressure of 1 atm.
Steady state
Metabolic condition in which concentrations of reactants and products are essentially constant, although individual reactions may not be at equilibrium.
Substrate
The reactant bound by an enzyme.
Substrate-level phosphorylation
Direct synthesis of ATP through the transfer of a phosphate group from a substrate to ADP.
Thermodynamics
Study of the changes in energy accompanying events in the physical universe.
Transduction
The incorporation of a gene into a cellular genome by means of a virus.
Transfer potential
A measure of the ability of a molecule to transfer any group to another molecule, with molecules having a higher affinity for the group being the better acceptors and molecules having a lower affinity better donors.
Transition state
The point during a chemical reaction at which bonds are being broken and reformed to yield products.
Tricarboxylic acid cycle (TCA cycle)
The circular metabolic pathway that oxidizes acetyl CoA, conserving its energy; the cycle is also known as the Krebs cycle or the citric acid cycle.
Turnover number
The maximum number of substrate molecules that can be converted to product by one enzyme molecule per unit of time.
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