An Introduction to Metabolism Flashcards
Metabolic Pathway
a series of defined steps (which are each catalyzed by a certain enzyme) which alters a specific molecule, resulting in a certain product
Catabolic Pathway
a metabolic pathway which releases energy via breakdown of complex compounds (ie: cellular respiration)
Anabolic Pathway
a metabolic pathway which consumes energy to build complex compounds (also called biosynthesis pathway)
Kinetic Energy
relative motion of objects
Thermal Energy
kinetic energy associated with random movement of atoms or molecules (such transfer from one object to other is called heat)
Potential Energy
An object is not moving and possesses energy due to its location or structure
Chemical Energy
the potential energy available for release in a chemical reaction (catabolic pathways harvest chemical energy)
First Law of Thermodynamics (the principle of conservation of energy)
Energy can be transferred and transformed, but it cannot be created or destroyed
Second Law of Thermodynamics
Every energy transfer or transformation increases the entropy of the universe
Free Energy
the portion of a system’s energy that can perform work when temperature and pressure are uniform
The Gibbs Free Energy Equation
Free Energy (Delta G) = The Change in Total Energy (Delta H) - Temperature in Kelvin * The Change in the Systems Enthalpy (Delta S)
Spontaneous Reaction
Unstable Systems like cells always become more stable (which explains diffusion and other phenomena), but never reach maximum stability, or equilibrium (such a stable state would mean work could not be performed, rendering the cell dead)
Exergonic Reaction
Energy outward (is a spontaneous reaction that does not require energy, Delta G is negative)
Endergonic Reaction
Energy Inward (is not spontaneous, energy required, Delta G is positive)
Chemical Work
The pushing of endergonic reactions that would not occur spontaneously (like the synthesis of polymers from monomers)
Transport Work
The pumping of substances across membranes against the direction of spontaneous movement (the concentration gradient)
Mechanical Work
the beating of cilia, the contraction of muscle cells, etc.
ATP Hydrolysis (Exergonic Reaction)
The bonds between the phosphate groups are broken through a dehydration reaction, ADP (Adenosine Diphosphate) is released
Energy Coupling
The use of an exergonic process to drive an endergonic process (cellular respiration drives many other chemical reactions)
Regeneration of ATP
ATP can be synthesized by adding a phosphate group to ADP, and uses the energy of catabolic processes to do so
Enzyme
a macromolecule that is a catalyst which speeds up a reaction without being consumed by the reaction
Activation Energy
the initial investment of energy required to start a reaction (which is absorbed by the molecules whose bonds are to be broken)
Transition State
The stage at which molecules have absorbed enough energy for their bonds to break
How Enzymes Speed Up Reactions
Enzymes lower the activation energy of the reaction (make molecules reach the transition state faster)
Substrate
the reactant an enzyme acts on and binds to; forms a enzyme-substrate complex, converts substrate to products of the reaction (or vice versa)
Active Site
The restricted region of the enzyme which binds to the substrate; held in place by weak interactions like hydrogen and ionic bonds
Cofactors
nonprotein helpers that help carry out catalytic activity (nonorganic like zinc, copper, and iron) or organic (coenzyme)
Competitive inhibitors
inhibit activity of enzyme by binding to active site so substrate cannot bind to enzyme
Non-Competitive Inhibitors
inhibit activity of enzyme by binding to enzyme away from active site (does not prevent substrate from binding) and limits active site efficiency
Allosteric Regulation
a protein’s function is affected by the binding of a regulatory molecule; most enzymes have multiple subunits, each with a polypeptide chain and active site, that oscillates between an active and inactive form
Activator
molecule that stabilizes active enzyme that has functional active sites
Inhibitor
molecules that stabilizes inactive enzyme
Cooperativity
a type of allosteric regulation where a substrate binds to one of multiple active sites, which amplifies the response of other subunits of the enzyme to substrates
Feedback Inhibition
type of metabolic control where a metabolic pathway is halted because of the inhibitory binding of its end product to an enzyme in the earlier stages of the pathway
