Chapter 6 - Exam 3 Flashcards
Coenzyme
complex organic or metalloorganic molecule that act as transient carriers of specific functional groups
Cofactor
1+ inorganic ions (Fe2+, Mg2+, Mn2+, or Zn2+)
Prosthetic Group
coenzyme or metal ion that is very tightly or covalently bound to the enzyme protein
Holoenzyme
complete catalytically active enzyme together with its bound coenzyme and/or metal ions
Apoenzyme
the protein part of a holoenzyme
Active Site
the location on the enzyme where the substrates bind
Substrate
the molecule that is bound to the active site and acted upon by the enzyme
Ground State
the starting point for the reaction
Transition State
the point at which decay to substrate or product is equally likely
Activation Energy
the difference between the energy at the ground state and the energy at the transition state
Keq
equilibrium between S (substrate) and P (product)
Change in ΔG during a reaction and how it relates to the function of enzymes.
ΔG: biochemical standard free energy change
-Enzymes lower activation energy (ΔG‡)of a reaction; increasing the rate of the reaction
Understand the relationship between delta G and Keq (when one is (–) the other is?)
inverse relationship; one is negative the other is positive
Positive Delta G
endergonic reaction (free energy is gained), smaller Keq
Negative Delta G
exergonic reaction (free energy is released), larger Keq
Higher Keq
reaction tends toward products
Lower Keq
reaction tends toward substrates
What is the binding energy of an enzyme and how does it relate to the function of the enzyme?
-energy derived from non-covalent enzyme-substrate interaction
-Major source of free energy used by enzymes to lower the activation energy
-The sum of the activation energy and the binding energy results in a lower net activation energy
Enzyme Kinetics
the discipline focused on determining the rate of a reaction and how it changes in response to changes in experimental parameters
Pre-Steady State
initial transient period during which ES builds up
Steady State
period during which ES and other intermediates remain constant
Vo, Initial Velocity
tangent to each curve taken at time = 0
Vmax
the plateau-like V0 region is close to the Vmax
Km (Michaelis-Menten Constant)
-Substrate concentration at which the reaction rate is half of its maximum (Vmax)
-Measurement of the affinity of an enzyme for its substrate
What is the relationship between Vmax and Km?
Km is ½ Vmax
Competitive Inhibition
-inhibitor competes with the substrate for the active site of an enzyme
-affects Km, but not Vmax
Uncompetitive Inhibition
-binds at a site distinct from the substrate active site…binds only to ES complex
-affects Vmax and Km
Mixed Inhibition
-binds at a site distinct from the substrate active site; binds to either E or the ES complex
-affects both the Km and the Vmax
Noncompetitive Inhibition
-binds at a site distinct from the substrate active site; binds to E or ES complex with equal affinity
-affects only Vmax
