Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

40 Cards in this Set

  • Front
  • Back
Catalysis depends on what structure of the enzyme?
depends on tertiary structure or the 3-D structure.
Kinetic vs. thermodynamics
Kinetic - reaction rates, how fast the reaction takes place
Thermo - energetic of a reaction, deta G.

these two are independent of each other.
Effect of catalytic amounts of enzyme on delta G.
small catalyst had on effect on delta G or the spontenaity of the reaction.

the catalyst is not consumed, therefore it can be cancelled out.
K = [B]c/[A]c
K is not affected, therefore, the delta G is alos not affected.
Activation energy
determines the rate of the reaction.
a catalyst lower the activtation barrier, allowing the reaction to proceed quicker.
How does a catalyst lower the transition state?
catalyst stabalizes the intermediate and lowers the amount of energy need to reach that intermediate.
Give an example of a unimolecule reaction.
radioactive decay.
Lock and Key vs. Induced fit model
Lock and Key - the substrate binds to a complementary active site. The exact fit of enzyme and substrate is a very stable structure, lowering the energy and causeing for an even greater need of energy to start the reaction.

Induced Fit - binding of sub. causes conf. change in active site of enzyme. This conf. change gives the transition state a higher energy.
The change in the substrate also helps activate the reaction.
Chymotrypsin as a model enzyme.
chymotrypsin catalyses the hydrolysis of peptide bonds as well as ester bonds.
Rate of the reaction gives a hyperbolic curve.
allosteric enzyme catalyst - gives a sigmoidal curve.
reation rate depends on the concentration of aspartate and forms CTP and UTP.
Michaelis-Menten equation
E+S = ES = E+P
Simplification of the M-M equation:
assume steady state
assume a catalytic amount of enzyme
assume that E and P do not react backwards to form ES
M-M graph equation
Vo = Vmax [S]/Km + [S]
M-M graph equation simplifications.
[S]>>Km - Vo=Vmax (zero order)

S<<Km - Vo = Vmax [S]/Km
(first order)

S=Km - Vo=Vmax/2 constant
How does Km affect affinty between enzyme and substrate.
the lower the Km - the more affinity the enzyme has for the substrate.
The M-M approach is for nonallosteric enzymes!
Lineweaver-Burk equation
1/Vo = (Km/Vmax)(1/[S] + (1/Vmax)

1/Vmax = at the + y axis
1/Km = at the - x axis
Slope of L-B equation
slope = Km/Vmax
How is Vmax related to the turn over number?
the turn over number
the number of moles of substrate the react to form product per mole of enzyme.

Kcat is equal to the turnover number.

the turnover number represents the efficency of the catalyst.

Kcat= Vmax/[E]
because Vmax=Kcat[E]
2 way to inhibit ezyymatic reaction.
through reversible or irreversible inhibitors.
reduce rate of enzyme.

molecules that interact with enzyme to reduce their rate.
Reversible inhibitors
can bind and then dissociate.

Competitive and Noncompetitive inhibitors.
Competative bind to active site - therefore, have structural similarities to the substrate.
bind to allosteric site and don't have similar strucutre to the substrate.
binding inactivates the enzyme.
Competative inhibitors:

competative inhibitor can be overcome by increasing the amount of substrate.
The Km value increases because you need more substrate to reach 1/2 V0.
Vmax is unaffected because you retain the same amount of enzyme.

the hyperbolic curve is lower in the presence of the competative inhibitor.

L-B plot - the lines with intersect at diff point on the x axis - giving diff. Km values.
Noncompetative inhibitors:

the inhibitor binds to the allosteric site. Therefore substrate cannot be increased to overcome this affect.

The Km value doesnot change. You still need the same amount of substrate to reach 1/2 Vo.

The Vmax value decreases because enzyme is being "removed" by the inhibitor. So, in effect you have less enzyme available.
Myoglobin and Chymotrypsin
ATCase and Hemoglobin
Myo. Chym - hyperbolic

Hb, ATCase - sigmoidal.
ATP actitives
CTP inhibits
Enzymes exist in 2 conf.
R- bind substrate tightly and is active
T-binds substrate lossely and is not-active.
Concerted Model
complete change from R to T.

lock and key
induced fit.
changing of one subunit affects the other subunits.
change to one subunit makes it easier for sequential changing to that subunit.
Allosteric systems have K system and V system.
K system - equivalent to competative inhibitors.
-the Km is lowered and the Vmax stays the same.

V system - noncompetative inhibitors.
the Vmax changes and the Km stays the same.
Sequential model has what coopertivity
S model has negative coopertivity that is unique to this model.
Apoenzyme - an ezyme that is missing its cofactor
Holofactor - enzyme that has its cofactor.

Cofactors are inorganic.
Coenzymes are organic.
Prostetic groups
tightly bound cofactors.
biotin - cofactor for pyruvate carboxylase and the reaction is carboxylation.

Vitamen precursor is biotin.
Coenzyme A
reaction type is acyl transfer.
involved in PDHC

vitamen precursor is pantophenic acid.

Lipoic acid - involved in acyl transfer.
had 2 sulfures that can make disulfide bonds.
Flavin coenzymes
Nicatinamide adinin
both ozidation/reduction .

nicatinamide comes form niacin
flavin come from favin.
aldehyde transfer.
involved with pyruvate dehydrogenase.

derived from thymine - vit. B1
NAD structure.
2 ribose
nicotinamide - vit portion

joined by a phosphoanhydride bond.

nicotinamide is the portion that is reduced.
Chemical reactions that occur in the active site
1. nucleophile
2. acid-base reactions
3. metal ion catalyst.
Metal ion catalyst
act as lewis acids and accept electrons for the carbonyl ozygen.
Make cabonyl carbon have detla positive and avaliable for nucleophillic attach.

Carboxypeptidase has a metal ion that aids in cleavage of the peptide bond at the C-terminus.