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Chapter 8
Vocabulary & Key Concepts
52
Biology
Undergraduate 1
10/22/2013

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Term
free energy
Definition
the amount of energy that is available to do work
Term
kinetic energy
Definition
energy of motion
Term
potential energy
Definition
energy that is associated with position or configuration
Term
first law of thermodynamics
Definition
energy is conserved; energy cannot be created or destroyed, but only transferred & transformed
Term
enthalpy
Definition
the total energy in a molecule (represented by H)
Term
exothermic
Definition
when a reaction releases heat energy (products have less potential energy than the reactants); deltaH is negative
Term
endothermic
Definition
if heat energy is taken up during the reaction, generating products that have higher potential energy than the reactants; deltaH is positive
Term
entropy
Definition
amount of disorder (symbolized by deltaS)
Term
second law of thermodynamics
Definition
total entropy always increases in an isolated system
Term
Gibbs free-energy change
Definition
deltaG = deltaH - T(deltaS)
Term
exergonic
Definition
spontaneous reactions; deltaG < 0
Term
endergonic
Definition
nonspontaneous reactions; deltaG > 0
Term
effect of concentration of reactants on number of collisions occurring between substances in a mixture
Definition
high concentration = more collisions (faster reactions)
Term
effect of temperature on number of collisions occurring between substances in a mixture
Definition
high temperature = more collisions (faster reactions)
Term
energetic coupling
Definition
between exergonic & endergonic reactions, chemical energy released from one reaction drives another
Term
reduction-oxidation reactions (redox reactions)
Definition
chemical reactions that involve the loss or gain of one or more electrons
Term
oxidation
Definition
loss of electrons
Term
reduction
Definition
gain of electrons
Term
electron donor
Definition
the atom in one molecule from which electrons may be transferred
Term
electron acceptor
Definition
the atom in one molecule to which electrons may be transferred
Term
flavin adenine dinucleotide (FAD)
Definition
a cellular electron acceptor that is reduced by two electrons accompanied by two protons to form FADH2 which then donates the high-energy electrons to other molecules
Term
electron carrier
Definition
a molecule that first accepts protons & electrons & then donates the electrons to other molecules
Term
nicotinamide adenine dinucleotide (NAD+)
Definition
common molecule that first accepts protons & electrons & then donates the electrons to other molecules
Term
NADH
Definition
reduced form of NAD+
Term
adenosine triphosphate (ATP)
Definition
makes things happen in cells because it has a great deal of potential energy
Term
kilocalorie (kcal)
Definition
raises 1 kilogram (kg) or water 1 degree C
Term
substrate
Definition
target molecule to which the cleaved phosphate from ATP hydrolyzation is transferred
Term
phosphorylation
Definition
the addition of a phosphate group to a substrate
Term
active site
Definition
the substrate binding site in enzymes in which substrate molecules are brought together
Term
induced fit
Definition
many enzymes undergo a significant change in shape (conformation) when reactant molecules bind to the active site
Term
transition state
Definition
a temporary, unstable, intermediate condition between the substrate & enzyme
Term
activation energy
Definition
the certain amount of kinetic energy required to strain the chemical bonds in substrates so they can achieve the transition state
Term
3 steps of enzyme action
Definition
1. initiation
2. transition state facilitation
3. termination
Term
initiation step of enzyme action (1)
Definition
reactants bind to the active site in a specific orientation, forming an enzyme-substrate complex
Term
transition state facilitation step of enzyme action (2)
Definition
interactions between enzyme & substrate lower the activation energy required
Term
termination step of enzyme action (3)
Definition
products have lower affinity for active site & are released; enzyme is unchanged after the reaction
Term
effect of increase in substrate concentration from low substrate concentrations on speed of an enzyme-catalyzed reaction
Definition
increase in steep, linear fashion
Term
effect of increase in substrate concentration from intermediate substrate concentrations on speed of an enzyme-catalyzed reaction
Definition
increase in speed begins to slow
Term
effect of increase in substrate concentration from high substrate concentrations on speed of an enzyme-catalyzed reaction
Definition
reaction rate plateaus at maximum speed
Term
3 types of enzyme "helpers"
Definition
1. cofactors
2. coenzymes
3. prosthetic groups
Term
cofactors
Definition
inorganic ions, such as the metal ions Zn2+ (zinc), Mg2+ (magnesium), & Fe2+ (iron), which reversibly interact with enzymes
Term
coenzymes
Definition
organic molecules that reversibly interact with enzymes, such as the electron carriers NADH or FADH2
Term
prosthetic groups
Definition
non-amino acid atoms or molecules that are permanently attached to proteins, such as the molecule retinal
Term
2 ways that reversible modifications affect enzyme function
Definition
1. the regulatory molecule is similar in size & shape to the enzyme's natural substrate & inhibits catalysis by binding to the enzyme's active site
2. the regulatory molecule binds at a location other than the active site & changes the shape of the enzyme
Term
competitive inhibition
Definition
the substrates cannot bind when a regulatory molecule binds to the enzyme's active site
Term
allosteric regulation
Definition
the active site becomes available/unavailable to the substrates when a regulatory molecule binds to a different site on the enzyme
Term
metabolic pathways
Definition
a series of reactions, each catalyzed by a different enzyme, that builds the molecules of life
Term
feedback inhibition
Definition
when an enzyme in a pathway is inhibited by the product of the reaction sequence
Term
3 steps of the retro-evolution hypothesis
Definition
1. enzyme 1 evolves to convert substrate 1 into a key produce involved in chemical evolution
2. substrate 1 is used up & a new enzymatic activity evolves to produce substrate 1 from another substrate
3. the cycle repeats
Term
bioremediation
Definition
a new technology that scrutinizes & engineers the metabolic activity of microbes to clean up a variety of human-made pollutants
Term
catabolic pathways
Definition
those that break down molecules for sources of energy & carbon building blocks
Term
anabolic pathways
Definition
those that use energy & carbon building blocks to synthesize molecules
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