Upgrade to remove ads
Only $35.99/year

Khan Academy MCAT - Enzymes and Activation Energy + Induced fit model of enzyme catalysis

Terms in this set (32)

enzymes
influence activation energy

use different catalytic strategies to make reactions go faster (acid/base, covalent, electrostatic, proximity/orientation)

bind to reactive groups

bind regulator at allosteric sites
reaction coordinate diagram
molecule's energy level is related to its stability

transition state of reactions is the highest energy point of the path from point A to B
molecule's energy level is related
its stability

something with lower energy states are more stable

something to transform into a more unstable form, it needs an input of energy to get there
transition state of a reaction
the weakening of the bonds in order to break them and form new bonds.

the arrangement of atoms that can easily go from reactants to products
transition state symbol
peak of a reaction coordinate diagram
free energy of activation
The amount of energy that reactants must absorb before a chemical reaction will start; also called activation energy.

the amount of energy needs to have in order to break the reaction barrier to ultimately be converted to point B
standard free energy change
the change in free energy that will occur for one unit of reaction if the reactants in their standard states are converted to products in their standard states

the net change in energy levels between our reactant and product. also the energy that is released into the environment once the reaction is over
reaction with a catalyst
with a catalyst, the activation energy barrier of molecule A to overcome to reach point B is much smaller

starting and ending points don't change
with a catalyst
the activation energy barrier of molecule A to overcome to reach point B is much smaller

transition state will have a much lower energy, meaning that it's more stable with an enzyme

reaction as a whole will have a much lower activation energy
starting and ending points
dont change

start and ending points are the same

only the path is changed

when point A doesn't equal point B, then the enzyme is not completely used up to catalyze the reaction

no permanent change to the enzyme after the reaction
enzymes are partially made of
proteins, along with unique active sites
substrates
any molecule that an enzyme will act on

usually the reactants that the enzyme will ultimately help turn into products through a reaction
active site
where the substrate binds to the enzyme

each enzyme has a unique active site that will bind to certain substrates
steps of an enzyme binding to a substrate
1. before binding
2. initial binding
3. induced fit
4. after reaction
5. product release
1. before binding step
enzymes are specific to certain substrates and certain reactions
2. initial binding
after binding, this step is imperfect, and substrate and enzyme don't fit exactly like a puzzle piece

act more like two pieces of clay that will mold over together, then fits more tighter than a puzzle piece eventually
3. induced fit
induced fit mold together and change shape a little more differently, so they can bind really tightly

catalyzation is at full force in this step
4. after reaction
after reacrion is completed, and binding becomes similar to stage two at initial binding

difference is that enzyme breaks substrate into two parts

with two parts separated after the reaction is finished, it's called the "after reaction"
5. product release
final stage is product of reactions released from enzyme, resembling the first step, except substrate is in two pieces
before binding equation
E + S
initial binding equation
ES
induced fit equation
[ E - X ]^(transition state)
after reaction equation
EP1P2
Product release equation
E + P1 + P2
binding is the strongest at the
transition state

since the enzyme and substrate have molded together

why it is called the induced fit (step 3)
some enzymes will bind to
more than one substrate

ex) lactic acid formation
Pyruvate + NADH --> Lactic acid + NAD+

enzymes don't necessarily bind to only one substrate
binding to other than active sites
sometimes, things will bind to enzymes at places other than their active sites, called allosteric binding
allosteric binding
- Substrate binds somewhere other than an enzymes active site
- Binds regulators (activators or inhibitors) at this site
- EX: inhibitor binds and changes enzymes shape --> affects its ability to catalyze rxns
an enzyme can change their active site when
a regulating enzyme, such as an inhibitor, making it hard to bind and catalyze the reactions

no longer able to bind to its intended substrate
allosteric sites
refer to any binding site outside of the active (binding) site

allosterically binding molecules can be either activators or inhibitors (any regulating molecules)
induced fit model
Change in the shape of an enzyme's active site that enhances the fit between the active site and its substrate(s)
active vs allosteric sites
active: where reaction takes place
allosteric: where regulation takes place
Sets found in the same folder