Unit 6. Enzymes and coenzymes Flashcards
The rate of the rxn is dependant on (5) things
Reaction concentration temp pH - [H+] activation E (NRG barrier) Product concentration
def:______: the cencentration of products cannot increase further
equilibrium state
What is Keq?
Equilibrium constant : [product]/[reactant]
Equilibrium constant can be calc. from _____ concentration or ratio of _____
equilibrium concentration
or
ratio of rate constants
______ must be greater than the NRG barrier for the rxn to proceed
activation NRG (Ea or delta G)
What is delta G?
activation NRG (Ea)
def: ____: when 2 reactants collide, NRG is released . It must be greater than the NRG barrier for the reaction to proceed
Activation NRG
_____: the amt of NRG required for the formation of products
Energy barrier
_____: how fast the products are formed
Reaction rate (or velocity) (v)
- must be measured very early in reaction (before reverse reaction )
When must the reaction rate be measured ?
before the reverse reaction occurs
_____: the difference btw the initial free NRG of the reactants and the products
Gibbs Free ENERGY
What determines the final concentration of the reactants and products ?
Delta G
- but not the reaction rate
If free NRG of product is lower than substrate the sign of Delta G will be ______ (+/-)
negative
If he free NRG of product is greater than substrate the sign of Delta G will be _____(+/-)
positive
______ effets the reaction rate
Activation NRG
_____ is when the product ends with less nrg than the initial reactant
exergonic
-Delta G
____ is when the product ends with more NRG than the initial reactant
endergonic
+Delta G
Standard state for : Moles, temp, pH and pressure
Moles: 1.0M
Temp: 25C or 298K
Pressure: 1atm
pH: 7.0
Is endergonic or exergonic spontaneous ?
exergonic
Catalyst ___ the rate of reaction
increase
Catalyst are ____ consumed
not
______ bind to substrate, lowering Ea
Catalyst
Can catalyst change Keq
No
Enzyme proteins can be _NA
RNA
The prosthetic group on an enzyme protein forms a _____
holoenzyme
If an enzyme protein prosthetic group is a metal it is a _______
metalloenzyme
_____ is an enzyme without a cofactor
apoprotein
An enzyme with optical specificity has the ability to __________
distinguish btw L- and D- forms of AA or sugars
Optical specificity is ________ specific
absolute
Specificity is dictated by the 3-D structure of the catalytic site of the enzyme and sunstrate it requires _______
3 point attachment
_____: substrate induces a conformational change in the catalytic site
induced fit model
3 pt attachment
Difference btw absolute and group specificity
absolute enzyme will only bind to one type of substrate (ex: fructokinase)
Grouped enzyme will bind to any type of substrate within a group (ex: hexokinase)
def: _______site : binds the reactants and facilitates the reaction
catalytic site
At least how many attachments must there be btw a substrate and enzyme
3 points of attachment
def___: the substrate fits exactly into the enzyme active site
lock and key
what are two models of substrate enzyme interactions
induced fit & lock and key
____ : increase the rate of reaction
activator (stimulator) enzymes
____: decreases the rate of reaction
inhibitor enzyme
____ is an intermediate and products of metabolism
metabolites
_______ compete with the natural metabolite for the active site of the enzyme
competitive inhibitors
Competitive inhibitors can be overcome by the addition of more _____
substrate
- Reversible
Irreversible enzymes fxn?
eliminate enzyme fxn
Name 5 properties of an enzyme
- catalyst
- proteins
- pH & tem dependent
- specific
- saturable
____ are secondary substrates that are required for the catalytic actions of certain enzymes
coenzymes (cosubstrates)
Vit. __ are coenzymes
Vit B
____ are secondary substrates
coenzymes
Coenzymes are required for the catalytic action of all enzymes T/F
false . only some
coenzymes can be ____ derivatives
vitamin
some ____ are covalently bound as prosthetic groups of enzymes
coenzymes
Name (3) inorganic coenzymes
Ca+, Na+, Cl-
Name (4) organic coenzymes
NAD?NADH
H+
FAD/FADH
CoASH
_____: substances other than substrates which regulate an enzyme’s activity by binding to the allosteric site
allosteric effectors or ligands
Allosteric effectors bind to _____ the regulate an enzymes activiry
allosteric site
The binding of an activator or inhibitor ____ especially the catalytic site, altering the reaction rate _____
Changes the enzyme conformation
exponentially
The main point of kinetics is to assess the ___ of an enzymatic reaction
velocity
_______: measures the velocity of a reaction, with increasing substrate concentrations, keeping pH an d temp at optimum
michaelis-menten equation
What factor is increased during a michaelis-menten equation
concentration of substrates
Lower the Km value, the ___ the affinity of the substrate to the enzyme
(michaelis-menten equation )
greater
Km = how strong of ___ an enzyme has for its substrate
michaelis-menten equation
affinity
The greater the Km, the _____ the affinity of an enzyme for its substrate
(michaelis-menten equation)
lower
_____ enzymes do redox reactions
oxidoreductase
_____ enzymes transfer R-groups
transferase
____ enzymes break substrates by addition of H2O
hydrolase
digestive enzymes
All digestive enzymes are _____
hydrolase
_____ enzymes break substrates w/o H2O
lyase
____ enzymes convert isomers
isomerase
they rearrange molecules
______ enzymes ligate with new covalent bonds
Ligase
synTHEtase/ synthase
Ligate means to ___
join
synTHEtase:______
uses ATP/GTP as NRG source
uses THE nrg
Synthase:_______
uses other sources of NRG
besides ATP/GTP
____: 2 or more enzymes that catalyze the same biochemical reaction
isozymes
_____: a proenzyme or an enzyme precursor
zymogen
(ex: enzymes in bile are inactive when they are in the prancrease, and activate after they leave the pancrease … so they dont eat the pancreas)
Isozymes are distinct, so they have _____AA sequences
different
and different physical properties
