Chapter 8 Flashcards
metabolic pathway
a series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule to simpler molecules (catholic pathway)
catabolic pathway
a metabolic pathway that releases energy by breaking down complex molecules to simpler molecules
anabolic pathway
a metabolic pathway that consumes energy to synthesize a complex molecule from a simpler molecule
bioenergetics
the study of how energy flows through living organisms
thermodynamics
the study of the energy transformations that occur in a collection of matter
first law of thermodynamics
energy of the universe is constant; it can be transferred and transformed, but it cannot be created or destroyed
entropy
a measure of molecular disorder or randomness
second law of thermodynamics
every energy transfer or transformation increases the entropy of the universe
spontaneous process
a process that leads to an increase in entropy and can proceed without requiring an input of energy
free energy
the portion of a system’s energy that can perform work when temperature and pressure are uniform throughout the system, as in a living cell
change in free energy equation
deltaG=deltaH-TdeltaS
change in free energy=change in enthalpy - temperature x change in entropy
exergonic reaction
net release of free energy
endergonic reaction
absorbs free energy from its surroundings
energy coupling
in cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction
ATP
contains the sugar ribose, with the nitrogenous base adenine and a chain of three phosphate groups (the triphosphate group) bonded to it
phosphorylated intermediate
a molecule (often a reactant) with a phosphate group covalently bound to it, making it more reactive (less stable) than the unphosphorylated molecule
enzyme
macromolecule that acts as a catalyst, a chemical agent that speeds up a reaction without being consumed by the reaction; cannot turn a reaction from exergonic to endergonic and vise versa
activation energy
the energy required to contort the reactant molecules so the bonds can break; the amount of energy needed to push the reactants to the top of an energy barrier
catalysis
the process where a catalyst selectively speeds up a reaction without being consumed
substrate
a reactant an enzyme acts on
enzyme substrate complex
a temporary complex formed when an enzyme binds to its substrate molecule(s)
active site
the specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs
induced fit
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
cofactor
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 and reversibly, along with the substrate, during catalysis
coenzyme
an organic molecule serving as a cofactor. most vitamins function as coenzymes in metabolic reactions
competitive inhibitors
reduce the productivity of enzymes by blocking substrates from entering active sites
noncompetitive inhibitors
do not directly compete with the substrate to bind to the enzyme at the active site. instead, they impede enzymatic reactions by binding to another part of the enzyme. this interaction causes the enzyme molecule to change its shape in such a way that the active site becomes much less effective at catalyzing the conversion of substrate to product
allosteric regulation
any case in which a protein’s function at one site is affected by the binding of a regulatory molecule to a separate site. it may result in either inhibition or stimulation of an enzyme’s activity
cooperativity
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
feedback inhibition
method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway
