Chapter 8 Flashcards
Metabolic pathway
begins with a specific molecule and ends with a product. Each is catalyzed by a specific enzyme
Catabolic pathways
release energy by breaking down complex molecules into simpler compounds
Anabolic pathways
consume energy to build complex molecules from simpler ones
Bioenergetics
the study of how energy flows through living organisms
Energy
the capacity to cause change
Kinetic energy
energy associated with motion
Thermal energy
The Kinetic energy associated with the random movement of molecules or atoms
Heat
thermal energy in transfer between objects
Potential energy
The energy matter possesses because of its location or structure
Chemical energy
potential energy available for release in a chemical reaction
Thermodynamics
the study of energy transformations that occur in a collection of matter
First Law of Thermodynamics
Energy can be transferred or transformed, but it cannot be created or destroyed
Second Law of Thermodynamics
Every energy transfer or transformation increases the entropy of the universe
entropy
a measure of molecular disorder, or randomness
Free Energy (ΔG)
the portion of a system’s energy that can perform work when temperature and. pressure are uniform throughout the system
Spontaneous processes
occur without energy input; they can happen quickly or slowly
ΔG=
ΔG= ΔH-TΔS
ΔH=change in total energy
ΔS=change in entropy
T=temperature in Kelvin
ΔG is negative
spontaneous process
ΔG is zero or positive
never spontaneous
The more free energy
the less stable a system is
exergonic reaction
proceeds with a net release of free energy and is spontaneous
endergonic reaction
absorbs free energy from its surroundings and is nonspontaneous
Reactions in a closed system…
eventually reach an equilibrium and can no longer do work
Open system
a material system in which mass or energy can be lost to or gained from the environment
Closed system
a natural physical system that does not allow transfer of matter in or out of the system
energy coupling
the use of an exergonic processto drive an endergonic one
ATP
Adenosine Triphosphate; the cell’s energy shuttle
ATP is composed of…
ribose (a sugar), adenine(a nitrogenous base), and three phosphate groups
_______ brakes the bond between ATP phosphate groups
Hydrolysis
Energy is released from ATP when…
the terminal phosphate bond is broken (This release of energy comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves)
phosphorylated intermediate
ATP drives endergonic reactions by phosphorylation, transferring a phosphate group to some other molecule, such as a reactant The recipient molecule is now called a phosphorylated intermediate
ATP is a renewable resource that is regenerated…
by addition of a phosphate group to adenosine diphosphate (ADP)
Enzymes
A catalytic protein, most which are specific to a certain reaction. Only a small amount are needed because they can be repeatedly used
Activation Energy (E subscript A)
or free energy of activation; the initial energy required to start a reaction (often supplied by thermal energy)
Catalysis
enzymes or other catalysts speed up specific reactions by lowering the activation energy barrier
Substrate
The reactant that an enzyme acts on
Enzyme-substate complex
what is formed when an enzyme binds to its substrate
Active site
the region on the enzyme where the substrate binds
catalytic cycle
The active site can lower an EA barrier by…
-orienting substrates correctly
-straining substrate bonds
-providing a favorable microenvironment
-covalently bonding to the substrate
The rate of an enzyme-catalyzed reaction can be sped up by…
increasing substrate concentration
saturated enzyme
when all enzyme molecules have their active sites engaged
Enzymes have optimal ______ and ______ they can operate in
temperature; pH
Cofactors
nonprotein enzyme helpers (may be inorganic [such as a metal in ionic form)] or organic [small molecules])
Enzyme inhibitors
Things that inhibit enzymes from functioning
Coenzyme
An organic cofactor
Competitive Inhibitors
bind to the active site of an enzyme, competing with the substrate
Noncompetitive inhibitors
bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective
Allosteric regulation
the term used to describe any case in which a protein’s function at one site is affected by the binding of a regulatory molecule to a separate sight
cooperativity
amplifies the response of enzymes to substrates
Feedback inhibition
when a metabolic pathway is halted by the inhibitory binding off its end product to an enzyme that acts early in the pathway
