unit 6 enzymes Flashcards
enzymes usually have what structure
tertiary
reactants aka
substrates
intermediates are not
isolatable/purifiable
rate of rxn dependent on
[reactants] temperature ph activation E and the energy barrier [products] (like if reach equilibrium)
catalysts help
lower energy barrier/activation energy, would make rxn more likely to occur
forward and reverse reactions occur
simultaneously at diff rates
() rxn rate are faster
initial
equilibrium state
concentration of products cannot increase further, forward and reverse reactions still occurring but NO NET CHANGE
equilibrium constant Keq
[products]/[reactants]
Keq=k1 (forward rxn) /k-1 (reverse rxn)
how Keq calculated
from equilibrium concentrations or ratio of rate constants
activation energy (Ea or delta G*)
when two reactants collide A+B, energy is realeased.
Must be greater than the energy barrier for the reaction to proceed
energy barrier
amount of energy required for the formation of products
what represents the net difference of energy
delta G
start low energy and end at high means it
cost us energy
+delta g means
cost us energy and is endergonic
-delta g means
released energy exorgonic
high energy to low means
released energy -G
reaction rate/ velocity
how fast the products are formed.
when measure velocity
very early in rxn (before reverse rxn)
units for velocity
mole/sec, umol/min
free energy change delta G (gibbs free energy)
difference between initial free energy of the reactants and products
delta g ultimately determines the
final concentrations of reactants and products BUT NOT THE REACTION RATE
what actually affects rate
activation energy
what is delta G0
change in free energy from standard state, 1.0 M concentrations of substrates and products to equilibrium
standard state STP
25 degrees C (298K) 1 stm ph 7
If free energy of products is lower than subtrates thes signs of delta G0 will be
negative -
if free energy is higher than products/products it will be
positive +
-delta g will occur () although () is not known
spontaneously, rate
enzymes are 6 things
- catalysts
- protein
- ph and temperature dependent
- specific
- saturable
- inhibitors, stimulators
catalysts 4 key things
increase rate of reaction
are not consumed
bind to substrates (reactants), lower Ea
don’t change Keq
things that like enzymes
bases, acids, metals, heat
enzymes are mostly
proteins
enzyme proteins are
rnas (ribozymes)
holoenzyme
enzyme proteins have a prosthetic group attached to a apoprotein
prosthesis means
to make something whole again
ex of holoenzyme
enzyme change shapes because of b12
metalloenzyme
a protein enzyme that prosthetic group is a metal
a type of holoenzyme
enzyme as ph and temperature dependent means
has optimal ph and temperatures, and chemicals that denature proteins denature enzyme activity
what kind of specificity do enzymes have
absolute (substrate) specificity or group specificity
or optical specificity
what is optical specificity
the ability to distinguish between L- and D- forms of amino acids or sugars
catalytic site
binds reactants and facilitates the reaction
specificity is dictated by the () of the enzyme and substrate
3-D structure of the catalytic site
cells require a minimum of () point attachment
3
induced fit means
the substrate changes conformation in the catalytic site (NOT lock and key modle)
what does it mean for the enzyme to be saturable
a reaction mixture (cytoplasm of cell) has a fixed amount of enzymes so the reaction rate increases with [substrate] to a point until all enzymes are busy
activator enzymes do what
increase rate of reaction
inhibitor enzymes do what
decrease rate of reaction
enzyme inhibitors are generally
structural analogs of metabolites
competitive inhibitors
inhibitor enzymes act by competing with the natural metabolite for the active site of the enzyme
reversible competitive inhibitors
effect can be overcome by addition of more natural substrate
enzyme binds to something like fake glucose but they can get off and go to real glucose
irreversible competitive inhibitors
it eliminates enzymes function, vmax is reduced
bind to fake glucose and cant get off
4 things coenzymes can be
- secondary substrates required for the catalytic actions of certain enzymes
- inorganic or organic
- vitamin derivative
- prosthetic groups of enzymes
ex of inorganic coenzymes
mg2+ ca2+ na+ cl-
ex of organic coenzymes
NAD/NADH+H, FAD/FADH2, coASH
what are the cofactors for B vitamins
NAD/NADH+H, FAD/FADH2, coASH
ex of coenzyme as vitamn derivative
B vitamins especially
how are the prosthetic groups of enzymes bounded
covalently (share electrons)
allosteric effectors or ligands
substances other than substrates which regulate an enzymes activity by binding to the allosteric site of the enzyme
what is an effector def
affects the effect of the enzyme
allosteric site def
catalytic site or another site of enzyme
binding the activator or inhibitor changes the enzymes () especially the catalytic site
conformation
a kinetic plot demonstrates a non-linear
S curve
positive allosteric kinetics shows
acceleration
negative allosteric kinectics shows
deceleration
binding of o2 to hemoglobin: when u bind one what else happens
you increase the chance of binding another
enzyme kinetics asses what
how velocity of an enzymatic reaction is affected bya host of factors including substrate concentration, coenzymes, activators, inhibitors, ph, temperature, phase of the moon…
experiments are done to obtain infor abouth
specificity of an enzyme for a particular substrate
mechanism of action.inhibition of enzyme activity
michaelis menten equation
measures velocity of a reaction with increasing substrate concentrations keeping ph and temperature at optimum
what is the actual michaelis menten equation
v=Vmax[S] / (Km+ [S])
the substrate with the () Km (michaelis) is favored
lower = greater affinity
what is Km
the [substrate] that produces a velocity of 1/2 max
= how strong an affinity an enzyme has for tis subtrate
lineweaver-burk (double reciprocal) plot
1/v = (Km/Vmax [S]) + 1/Vmax
aka y=mx+b’p[;
what does lineweaver-burk remove
removes the uncertainty of the vmax plateau of michaelis-menten eq.
with lineweaver burk plot how do u find vmax
when u hit the velocity/y axis
with lineweavers burk plot how get km
when it his the substrate axis
michaelis menten and lineweaver burk are only good for () kinets because additional substrate binding (o2 to hb) may alter rate of reaction
non-allosteric
what are the 4 types of enzme naming
trivial name (chymotrypsin) hybrid name (substrate + ase) descriptive name (substrate + description + ase lactate dehydrogenase) IUB systematic classification and nomenclature