unit 6 enzymes Flashcards by Marissa Palmer

enzymes usually have what structure

tertiary

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reactants aka

substrates

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intermediates are not

isolatable/purifiable

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rate of rxn dependent on

[reactants]
temperature
ph
activation E and the energy barrier
[products] (like if reach equilibrium)

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catalysts help

lower energy barrier/activation energy, would make rxn more likely to occur

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forward and reverse reactions occur

simultaneously at diff rates

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() rxn rate are faster

initial

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equilibrium state

concentration of products cannot increase further, forward and reverse reactions still occurring but NO NET CHANGE

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equilibrium constant Keq

[products]/[reactants]

Keq=k1 (forward rxn) /k-1 (reverse rxn)

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how Keq calculated

from equilibrium concentrations or ratio of rate constants

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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

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energy barrier

amount of energy required for the formation of products

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what represents the net difference of energy

delta G

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start low energy and end at high means it

cost us energy

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+delta g means

cost us energy and is endergonic

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-delta g means

released energy exorgonic

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high energy to low means

released energy -G

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reaction rate/ velocity

how fast the products are formed.

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when measure velocity

very early in rxn (before reverse rxn)

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units for velocity

mole/sec, umol/min

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free energy change delta G (gibbs free energy)

difference between initial free energy of the reactants and products

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delta g ultimately determines the

final concentrations of reactants and products BUT NOT THE REACTION RATE

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what actually affects rate

activation energy

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what is delta G0

change in free energy from standard state, 1.0 M concentrations of substrates and products to equilibrium

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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

1. catalysts 2. protein 3. ph and temperature dependent 4. specific 5. saturable 6. 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

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

1. secondary substrates required for the catalytic actions of certain enzymes 2. inorganic or organic 3. vitamin derivative 4. 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 ```

unit 6 enzymes Flashcards

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