Enzymes Flashcards

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1
Q

Enzymes

A

Biological catalysts that do not impact the thermodynamics of a biological rxn but increase the rate at which it occurs

  • Lowers the activation energy
  • Does not change free energy (G) or enthalpy (H)
  • Does not alter equilibrium
  • Changes rate of rxn (kinetics)
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2
Q

Lock and Key Model

A

Enzyme active site (lock) is already in the appropriate conformation for the substrate (key) to bind

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3
Q

Induced Fit Model

A

Shape of the active site becomes truly complementary only after the substrate begins binding. These enzymes return to their original shape after the substrate leaves

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4
Q

Cofactors

A

Inorganic molecules and metal ions

  • Small so that they can bind to the active site of an enzyme to aid in conformation change. Participate in catalysis by carrying charge through the ionization, polarization or depolarization
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5
Q

CoEnzymes

A

Organic molecules

  • Small so that they can bind to the active site of an enzyme to aid in conformation change. Participate in catalysis by carrying charge through the ionization, polarization or depolarization
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6
Q

Saturation

A

All enzyme active sites are occupied by the substrate

As [substrate] increases, the reaction rate also increases until Vmax is reached

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7
Q

Vmax

A

Maximum velocity of reaction; only increased by increasing the [Enzyme]

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8
Q

Michaelis-Menten

A

E+S ES —-> E+P

Vmax [S]
________ = V
Km + [S]

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9
Q

Km

A

Measure of the affinity of an enzyme for its substrate

Increased Km means decreased affinity because
Km = 1/2 Vmax = [S]

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10
Q

Competitive Inhibition

A

Binds to E at the Active Site
Increases Km
Vmax remains unchanged

**Overcome by adding excess Substrate

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11
Q

NonCompetitive Inhibition

A

Binds to E and ES at an Allosteric Site
Km Remains unchanged
Vmax Decreases

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12
Q

Uncompetitive Inhibition

A

Binds to ES at an Allosteric Site
Km decreases
Vmax Decreases

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13
Q

Mixed Inhibition

A

Binds to E and ES at Allosteric Site
Km can increase or decrease
Vmax Decreases

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14
Q

Feedback Regulation

A

Regulation by products created further down in the pathway

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15
Q

Feed Forward Regulation

A

Intermediates preceding the enzyme are the regulators

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16
Q

Negative Feedback Regulation

A

Product binds to the active site of an enzyme earlier in the pathway inhibiting them or making them unavailable

17
Q

Allosteric Enzymes

A

Contain multiple binding sites

18
Q

Covalently Modified Enzymes

A

Transient - allosteric activation / inhibition

Covalent - glycoslation / phosphorylation

19
Q

Zymogens

A

Inactive Enzyme; contain a regulatory domain which must be removed or altered to expose the active site

20
Q

Ligases

A

Responsible for joining two large biomolecules (often of the same type)

21
Q

Isomerases

A

Catalyze the interconversion of isomers, including both constitutional and stereoisomers

22
Q

Lyases

A

Catalyze cleavage without the addition of water and without the transfer of electrons

*Reverse rxn = synthesis

23
Q

Hydrolases

A

Catalyze cleavage with the addition of water

24
Q

Oxidoreductases

A

Catalyze oxidation - reduction reactions that involve the transfer of electrons

25
Q

Transferases

A

Move a functional group from one molecule to another molecule