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MCAT Biochem Review > Chapter 2: Enzymes > Flashcards

Chapter 2: Enzymes Flashcards

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MCAT flashcards
1
Q

Enzymes act as catalysts to impact which of the following in a reaction: thermodynamics, equilibrium position, and reaction rate

A

Rate of reaction

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2
Q

What are the key features of an enzyme? (7)

A
  1. lower the activation energy
  2. increase rate of reaction
  3. do not alter equilibrium constant
  4. are not changed or consumed in the reaction
  5. are pH- and temperature-sensitive, with optimal activity at specific pH ranges and temperatures
  6. Do not affect the overall delta G of the reaction
  7. Are specific for a particular reaction or class of reactions
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3
Q

The molecules upon which an enzyme acts are called:

A

Substrates

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4
Q

What are the six categories of enzymes? (hint: Lil hot)

A
  1. Ligases
  2. Isomerases
  3. Lyases
  4. Hydrolases
  5. Oxireductases
  6. Transferases
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5
Q

How do cofactors and coenzymes differ?

A

Cofactors are generally metal cations, and coenzymes are small organic molecules that are generally derived from vitamins.

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6
Q

Enzymes that require a cofactor but do not have them are called:

A

Apoenzymes

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7
Q

Enzymes that require a cofactor and do contain them are called:

A

Holoenzymes

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8
Q

Enzymes that are secreted in an inactive form with a regulatory domain that must be removed or altered to become active are called:

A

Zymogens

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9
Q

What is the function of oxidoreductases?

A

Catalyze oxidation-reduction reactions; i.e., the transfer of electrons between two biological molecules.

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10
Q

What is the function of transferases?

A

Catalyze the movement of a functional group from one molecule to another

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11
Q

What is the function of kinases?

A

Catalyze the transfer of a phosphate group to another molecule (generally from ATP to another molecule)

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12
Q

What is the function of hydrolyses?

A

Catalyze the breaking of a compound into two molecules using the addition of water

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13
Q

What is the function of lyases?

A

Catalyze the cleavage of a single molecule into two products without water. In reverse, they act as synthases. Generally act upon smaller molecules.

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14
Q

What is the function of isomerases?

A

Catalyze the rearrangement of bonds within a molecule

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15
Q

What is the function of ligases?

A

Catalyze addition or synthesis reactions, generally between large similar molecules and often requiring ATP.

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16
Q

Define Vmax

A

the maximum velocity of an enzyme, found at saturation

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17
Q

Define Km

A

The substrate concentration at which 1/2 of the enzymes are full

18
Q

What is the michaelis-mentin equation

A

V= (Vmax[S])/(Km+[S])

19
Q

What is the equation for Vmax of an enzyme?

A

Vmax = [E]Kcat

20
Q

In a Lineweaver-Burk plot, what value is found at the intercept of the line with the x-axis?

A

-1/Km

21
Q

What is a Lineweaver-Burk plot?

A

a double reciprocal graph of the Michaelis-Menten equation

22
Q

In a Lineweaver-Burk plot, what value is found at the intercept of the line with the y-axis?

A

1/Vmax

23
Q

What is positive cooperative binding?

A

Substrate binding that increases the affinity for a subsequent substrate

24
Q

What is negative cooperative binding?

A

Substrate binding that decreases affinity for subsequent substrate

25
Q

What is Hill’s coefficient?

A

A quantifiable numerical value that indicates cooperativity

26
Q

Hill’s coefficient > 1 means what?

A

Positive cooperative binding

27
Q

Hill’s coefficient < 1 means what?

A

Negative cooperative binding

28
Q

Hill’s coefficient = 1 means what?

A

No cooperative binding

29
Q

A maximally efficient enzyme has a (high/low) Kcat and a (high/low) Km

A

High Kcat and low Km

30
Q

What is the variable for catalytic turnover?

A

Kcat

31
Q

What is the variable for substrate affinity?

A

Km

32
Q

How do we find the catalytic efficiency of an enzyme?

A

Kcat/Km

33
Q

An increase in Km indicates what?

A

Decrease in affinity

34
Q

What is the ideal pH for most enzymes in the body?

A

7.4

35
Q

Competitive inhibitor binding site and impact on Km and Vmax

A

Active site on E
Increases Km
No impact on Vmax

36
Q

Noncompetitive inhibitor binding site and impact on Km and Vmax

A

Allosteric site on E or ES
No impact on Km
Decreases Vmax

37
Q

Mixed inhibitor binding site and impact on Km and Vmax

A

Allosteric site on E or ES
Increases or decreases Km
Decreases Vmax

38
Q

Uncompetitive inhibitor binding site and impact on Km and Vmax

A

Allosteric site on ES
Decreases Km
Decreases Vmax

39
Q

Define irreversible inhibition

A

Inhibition that permanently makes an active site unavailable

40
Q

Phosphorylation is an example of what type of enzyme modification?

A

Covalent modification

41
Q

Define zymogens

A

Inactive enzymes with a catalytic (active) and a regulatory domain, the latter of which must be removed or altered to expose the active site

MCAT Biochem Review (3 decks)

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