Ch.22 Flashcards
how do grignards work
pg. 3
they add on to a carbonyl
describe how enzymes are catalysts
pg. 4
enzymes are proteins that catalyze chemical reactions. these are generally globular proteins meaning they fold up to create a perfect chemical environment for a specific region
draw reaction coordinate diagram that displays when a catalyst is or isn’t present
pg. 4
positive delta G
endergonic
draw the mechanism of a proton based acid catalyst
pg. 5
where is the most nucleophilic site on the compound on pg. 5 and why is that the most nucleophilic location
most nucleophilic location because its stabilized via resonance compared to the other oxygen (which if you tried to stabilize that other oxygen via resonance youd get a texas oxygen)
specific vs. general catalysis
pg. 6
specific catalysis: reactant or intermediated fully protonated after rate determining step
general catalysis: proton transfer takes place during the rate determining step (partial proton transfer: simultaneous protonation and bond breaking / forming to form the transition state)
draw the difference in mechanism between specific and general catalysis on pg. 6
draw the difference in reaction coordinate diagrams between specific and general catalysis
pg.6
how metals affect acidity
pg. 8
metals are positive cations and when they bind to a compound, the compound becomes more acidic (more electrophilic)
draw the general catalysis example on pg. 9
draw the difference between specific and general catalysis under basic conditions
pg. 10
what is the difference between specific and general catalysis under basic conditions
pg. 10
general catalysis is not as highly reactive compared to the specific mechanism
answer the question on pg. 12
what is something you have to be cognizant of in terms of catalysis in the active site
pg. 13
you also have to be careful of lewis acids in the enzyme active site (ex. other metals that interact with Zn2+). These are other points of acidity.
how do amino acids engage in catalysis
pg. 13
AAs need to have the right charges; general pH is 7.4 when considering the conjugates and for thinking about the catalytic roles
draw how a mechanism can be changed to a more favorable pathway
pg.14
draw the general redox mechanism and catalysis
pg.16
NAD+
pg.16
NAD+ is an oxidizing agent
the catalytic triad
pg.17
a set of three coordinated amino acids that can be found in the active site of some enzymes
proton shuttle
pg. 17
a molecule that protonates something at one point and deprotonates at another point in the mechanism
answer practice question on pg. 19
answer practice question on pg. 20
answer practice question on pg. 21
answer practice question on pg. 22
draw the usage of NAD+
pg. 23
where is catalytic activity manifested
pg. 24
the active site of the enzyme
what produces catalytic activity
pg. 24
the folding pattern of the enzyme
what type of binding occurs in the active site
pg.25
H-bonding
hydrophobic pockets
salt bridges
pi-interactions
alcohol dehydrogenous
pg. 26
responsible for metabolizing the bulk of ethanol consumed as part of the diet
draw the general mechanism for alcohol dehydrogenase
pg. 27
absolute specificity
pg. 28
enzymes can be very specific for a single substrate – absolute specificity would mean that a substrate has near perfect interactions for its specific structure
relative specificity
pg. 28
enzymes that can catalyze a range of substrates
how can enzymes have relative specificity
pg. 28
most enzymes can catalyze a range of substrates having the same functional groups. they can also select based on stereochemistry (stereospecificity)
Km
is the substrate concentration at which half of an enzyme is saturated and the reaction rate is 50% of Vmax. Km is a measure of how much an enzyme is attracted to its substrate. A lower Km value means the enzyme is more efficient at carrying out its function at a lower substrate concentration.
(lower Km = more affinity of a compound for the active site)
relative maximum velocity (Vmax)
the maximum rate of reaction (the fastest ability for an enzyme to do the rxn)
draw the utility of lipase in the lab
pg. 29
lipase is a well known stereospecific enzyme – it is used in the lab to isolate one enantiomer over the other. draw its uses
absolute vs. relative specificity in the formation of a product
pg. 31
absolute –> one pdt
relative –> multiple pdts
explain / draw the lock and key model
pg. 32
the substrate entering the active site of the enzyme creates an enzyme/substrate complex. the enzyme changes shape slightly as the substrate binds which forms the enzyme/product complex. the products leave the active site of the enzyme
what is the ideal enzyme catalysis pH
7.4
what is the ideal enzyme catalysis temperature
37 degrees celcius
answer the question on slide 34. when would the answer be none of the above?
relative specificity –> the twodselected compounss are close enough to ethanal.
the answer would be E if you were attempting with absolute specificit –> the compound would HAVE to be an ethanal
what controls the rate of a reaction
pg. 35
activation energy (lower activation energy enhances rate)
how do enzymes effect activation energy and reaction rate
pg. 35
enzymes lower the activation which speeds up the reaction
how can you increase the rate of the forward reaction
pg. 35
- add heat (in bio you can’t do that)
- raise concentration –> you can sort of do this in bio
- add a catalyst –> you can do this in bio
michaelis-menten kinetics
pg. 36 / 37
there is a limit to how fast the forward reaction goes
as the substrate increases, its interaction with the enzyme increases; but, you reach a point where all the active sites are filled, which doesn’t give any higher interactions (maximal velocity)
what does 1/2 vmax tell you
pg. 38
how well the enzyme binds to the active site
what changes vmax or km
pg. 39
- the substrate
- the pH
- the temperature
if comparing two kms - one is 0.006 and the other is 57 - what does this tell us
pg. 39
the compound with a km of 0.006 binds to the active site quicker than the compound with the km of 57
how might an enzyme be inhibited (overall)
pg. 42
enzyme can be slowed and/or stopped not only by denaturation but by small molecules and other chemicals. any chemical that interferes with an enzymes catalytic ability is an inhibitor
what are the three types of inhibitors
pg. 42
- competitive inhibition
- non-competitive inhibition
- covalent inhibition
describe competitive inhibition
pg. 44
involves a direct assault on the active site. if the inhibitor is in the active site, the substrate cannot be.
what are the kinetic effects of competitive inhibition
pg. 45
competitive inhibitors raise km but do not change the vmax
Increased km: More substrate is required to achieve half of vmax due to the competitive inhibition.
Unchanged vmax: The maximum velocity remains the same because, at high substrate concentrations, the inhibitor’s effect is negated.
This is why competitive inhibition raises km but does not change vmax
.
describe covatent inhibition
pg. 47
irreversibly bind to the active site
