Chapter 8 Flashcards
A metabolic pathway begins with a specific molecule, which is then altered in a series of defined steps, resulting in a certain product. Each step of the pathway is catalyzed by a specific enzyme.
True
Catabolic pathways (breakdown pathways)
-Degradative processes
Metabolic pathways that release energy by breaking down complex molecules to simpler compounds.
Anabolic pathways (bio synthetic pathways)
Consume energy to build complicated molecules from simpler ones
Catabolic and anabolic pathways are the “downhill” and “uphill” avenues of the metabolic landscape.
True
Downhill reactions = Catabolic pathways
Uphill reactions = Anabolic pathways
Bioenergetics
The study of how energy flows through living organisms
Chemical energy
Refers to the potential energy available for release in a chemical reaction.
Thermodynamics
The study of the energy transformations that occur in a collection of matter.
First law of thermodynamics
Principle of conservation of energy
Energy can be transferred and transformed, but it cannot be created or destroyed.
Entropy
A measure of disorder, or randomness.
The more randomly arranged a collection of matter is, the greater its entropy.
Second law of thermodynamics
Every energy transfer or transformation increases the entropy of the universe.
Spontaneous process (energetically favorable process)
If a given process, by itself, leads to an increase in entropy, that process can proceed without requiring an input of energy.
A process that, considered on its own, leads to a decrease in entropy is said to be __________
Nonspontaneous
Free energy (Gibbs free energy of a system)
-symbolized by the letter “G”
Is 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.
Formula for ΔG
ΔG = ΔH — TΔS
ΔH symbolizes…
The change in a systems enthalpy (in biological systems, equivalent to total energy)
ΔS symbolizes…
Change in the system’s entropy
T symbolizes
The absolute temperature in Kelvin (K) units
K = •C + 273
True
Only processes with a ______________ are spontaneous
negative ΔG
Every spontaneous process decreases the system’s free energy, and processes that have a positive or zero ΔG are never spontaneous.
True
A process is spontaneous and can perform work only when it is moving toward equilibrium.
True
Exergonic reaction
Net release of free energy
ΔG is negative
-Occurs spontaneously
Endergonic reaction
Absorbs free energy from its surroundings
-Is non spontaneous
Chemical work
The pushing of endergonic reactions that would not occur spontaneously, such as the synthesis of polymers from monomers.
Transport work
The pumping of substances across membranes against the direction of spontaneous movement.
Mechanical work such as…
The beating of cilia, the contraction of muscle cells, and the movement of chromosomes during cellular reproduction.
Energy coupling
The use of an exergonic process to drive an endergonic one.
Phosphorylation
The transfer of a phosphate group from ATP to some other molecule
Phosphorylated intermediate
The recipient molecule with the phosphate group covalently bonded to it
To reach the contorted state where bonds can change, reactant molecules must absorb energy from their surroundings.
True
Activation energy (free energy of activation)
The energy required to contort the reactant molecules so the bonds can break.
Transition state
When the molecules have absorbed enough energy for the bonds to break.
The activation energy provides a barrier that determines the rate of the reaction
True
An enzyme catalyzes a reaction by…
Lowering the activation energy barrier
Substrate
The reaction an enzyme acts on
Active site
Region on the surface of the enzyme where catalysis occurs.
Cofactors
Nonprotein enzyme helpers
Coenzyme
A cofactor that is an organic molecule.
Competitive inhibitors
“Mimics” that reduce the productivity of enzymes by blocking substrates from entering active sites.
Noncompetitive inhibitors
Bind to another part of the enzyme, which changes its shape in such a way that the active site becomes less effective at catalyzing.
Allosteric regulation
Is the term used to describe any case in which a protein’s function at one site is affected by the bonding of a regulatory molecule to a separate site.
Feedback inhibition
A metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathway.
