Chapter 8: An Introduction To Metabolism Flashcards
Thermodynamics
The study of energy transformation that occur in a collection of matter
First law of thermodynamics
The principle of conservation of energy’s; energy can be transferred and transformed but it cannot be created or destroyed.
Second law of thermodynamics
The principal stating that every energy transfer or transformation increases the entropy of the universe. Usable forms of energy are at least partly converted to heat.
Spontaneous process
A process that occurs without an overall input of energy; a process that is energetically favorable.
Metabolism
The totality of an organism’s chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism.
Catabolic pathways
A metabolic pathway that releases energy by breaking down complex molecules into simpler molecules
Anabolic Pathways
A metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules
Free energy change
The portion of a biological system’s energy that can perform work when temperature and pressure are uniform throughout the system.
DeltaG = Gfinal -G initial
Can be thought of as a measure of a system’s instability, or its tendency to change to a more stable state.
- systems with more free energy are less stable and more likely to change.
Equilibrium
State of maximum stability. Reverse reaction rate and forwards reaction rate are the same so there is no net change
- free energy increases when the reaction is pushed away from equilibrium
- changes away from equilibrium are never spontaneous
Exergonic reaction
A spontaneous chemical reaction in which there is a net release of free energy
Delta G is negative
Endergonic Reaction
A non spontaneous chemical reaction in which free energy is absorbed from the surroundings
- Delta G is positive
Energy Coupling
The use of energy released from an exergonic reaction to drive an endergonic reaction
Phosphorylation
The transfer of a phosphate group from ATP to some other molecule, such as the reactant
Phosphorylated intermediate
A molecule, often a reactant, with a phosphate group covalently bound to it, making it more reactive than the unphosphorylated molecule
Enzyme
A macromolecule, often a protein, serving as a catalyst
Catalyst
A chemical event that selectively increases the rate of reaction without being consumed by the reaction
Activation energy
The amount of energy that reactants must absorb before a chemical reaction will start; also called free energy of activation
Transition state
When molecules in a reaction have absorbed enough energy for the bonds to break and the reactants are in an unstable condition
Catalysis
A process by which a catalyst selectively increases the rate of reaction without being consumed by the reaction. This is done through the enzyme lowering the energy of activation barrier
Substrate
The reactant on which an enzyme works
Enzyme-substrate complex
A temporary complex formed when an enzyme binds to its substrate molecule
Active site
The specific region of an enzyme that binds to the substrate and formed the pocket in which catalysis occurs
Induced fit
Caused by the entry of the substrate, the change in shape of the active site of an enzyme so that it binds more snugly to the substrate
Specificity of Enzymes
Due to the complementary fit between the shape of its active site and the shape of the substrate
Cofactor
Any non protein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can permanently bound to the active site or may bind loosely and reversible, along with the substrate, during catalysis.
Coenzyme
An organic molecule serving as a cofactors. Most vitamins function as coenzymes in metabolic reactions
Competitive Inhibitors
A substance that reduces the activity of an enzyme by entering the active site in place of the substrate, whose structure it mimics
Non competitive inhibitor
A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing the enzyme’s shape so that the active site no longer effectively catalyzes the conversion of substrate to product
Allosteric Regulation
The binding of a regulatory molecule to a protein at one site that affects the function of a protein at a different site
Activator
A regulatory molecule that, which it binds to a regulatory site, stabilizes the shape that has functional active sites
Inhibitor
A regulatory Molecule that, when it binds to a regulatory site, stabilizes the inactive form of the enzyme
Cooperativity
A kind of allosteric regulation whereby a shape change in one subunit of a protein caused by substrate binding is transmitted to all other subunits, facilitating the binding of additional substrate molecules to those subunits
Feedback Inhibition
A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway
