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MCAT BIOCHEM > Enzymes > Flashcards

Enzymes Flashcards

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MCAT flashcards
1
Q

Functions of enzymes:
_______ activation energy.
_______ rate of reaction.
______ alter the equilibrium constant.
__________ changed or consumed in the reaction.
Are ______ and _____ sensitive, with optimal activity at specific ______ ranges and ________.
______ affect the overall ΔG of the rxn.
Are _____ for a particular reaction or class of reactions.

A

LOWER activation energy.
INCREASE rate of reaction.
DO NOT alter the equilibrium constant.
ARE NOT changed or consumed in the reaction.
Are pH and TEMPERATURE sensitive, with optimal activity at specific pH ranges and TEMPERATURES.
DO NOT affect the overall ΔG of the rxn.
Are SPECIFIC for a particular reaction or class of reactions.

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2
Q

Ligase

A

Addition or synthesis rxns. Generally btwn large molecules. Often Require ATP.

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3
Q

Isomerase

A

Rearrangement of bonds within a compound (constitutional isomers and stereoisomers)

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4
Q

Lyase

A

Cleavage of a single molecule into two products (without the addition of water or transfer of electrons) OR synthesis of small organic molecules

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5
Q

Hydrolase

A

Breaking of a compound into two molecules using the addition of water

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6
Q

Oxidoreductase

A

Redox reactions (transfer of electrons)

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7
Q

Transferase

A

Movement of a fxl group from one molecule to another

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8
Q

Lipase

A

Catalyze the hydrolysis of fats. Dietary fats are broken down into FAs and glycerol (or other alcohols).

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9
Q

Kinases

A

Add a phosphate group. Type of transferase.

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10
Q

Phosphatases

A

Remove a phosphate group. Type of transferase.

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11
Q

Phosphorylases

A

Introduces a phosphate group into an organic molecule, notably glucose.

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12
Q

Exergonic Rxns

A

Release Energy, - ΔG

*** add image

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13
Q

Endergonic Rxns

A

Require Energy, + ΔG

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14
Q

As [S] increases,

A

Rate of the reaction increases until a maximum value is reached

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15
Q

Km

A

[S] at which an enzyme runs at half Vmax

=(K-1 + K-2)/K1

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16
Q

Vmax

A

the max rate at which an enzyme can catalyze a reaction. When all enzyme active sites are saturated with substrate.

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17
Q

Cooperative Enzymes

A

Sigmoidal curve due to change in activity with substrate binding; phenomenon in which the shape of one subunit of an enzyme consisting of several subunits is altered by the substrate
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18
Q

M-M plot

A

Hyperbolic curve

**add image

19
Q

Lineweaver-Burk plot

A

Line

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20
Q

Competitive Inhibition

A 
When the inhibitor is similar to the substrate and binds to the active site. Can be overcome by increasing [S].
Binding SIte: Active site
Impact on Km: Increases
Impact on Vmax: No change
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21
Q

Noncompetitive Inhibition

A 
The inhibitor binds with equal affinity to E and E-S complex.
Binding SIte: Allosteric site
Impact on Km: No change
Impact on Vmax: Decreases
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22
Q

Mixed Inhibition

A

When inhibitor binds with unequal affinity to E and E-S complex
Binding SIte: Allosteric Site
Impact on Km: Increases or Decreases (depending on inhibitor affinity for E vs. E-S)
Impact on Vmax: Decreased
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23
Q

Uncompetitive Inhibition

A

Binding SIte: E-S Complex
Impact on Km: Decreases
Impact on Vmax: Decreases
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24
Q

Reversible Inhibition

A

Ability to replace the inhibitor with a compound of greater affinity or to remove it using mild lab treatment. Types: Competitive, noncompetitive, mixed, and uncompetitive

25
Q

Irreversible Inhibition

A

Alters the enzyme in a way that the active site is unavailable for a prolonged duration or permanently

26
Q

High Km

A

Low affinity

27
Q

Low Km

A

High affinity

28
Q

suicide inhibitor

A

a substrate analogue that binds IRREVERSIBLY to the active site via a covalent bond

29
Q

Feedback inhibition

A

E inhibited by high levels of product from later in the pathway

30
Q

Allosteric Effector

A

Binds at the allosteric site and induces a change in the conformation of the enzyme so that the substrate can no longer bind to the active site. Displays cooperativity (does not obey M-M kinetics).

31
Q

Homotropic Effector

A

An allosteric regulator that is also the substrate. (Ex: O2 is a homotropic allosteric regulator of Hgb aka as O2 increases, increase in R state molecules OR ATP in Glycolysis)
-Affects SHAPE of curve

32
Q

Heterotropic Effector

A

An allosteric regulator that is different from the substrate.(Ex: 2,3-BPG and CO2 with Hgb OR AMP in glycolysis)
-Affects Km of curve

33
Q

Effects of local conditions on enzymes

temperature, pH, and salinity

A

Temp and pH can affect E activity in vivo, denaturing the E and leading to loss of secondary, tertiary, and quaternary structure.
Salinity can impact action of E in vitro

34
Q

Lock and Key Theory

A

E and S are exactly complementary and fit together like a key into a lock
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35
Q

Induced Fit Theory

A

E and S undergo conformational changed to interact fully

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36
Q

Cofactors

A

Metal cation that is required by some enzymes

37
Q

Coenzyme

A

Organic molecule that is required by some enzymes

38
Q

Phosphorylation

A
  • covalent modification with phosphate
  • can alter the activity or selectivity of the enzyme
  • Catabolism: Phosphorylated = active
  • Anabolism: Phosphorylated = inactive
39
Q

Glycosylation

A
  • covalent modification with carb

- can alter the activity or selectivity of the enzyme

40
Q

Zymogens

A

Precursor to an enzyme. Secreted in inactive form and are activated by cleavage.

41
Q

Reaction Scheme for M-M kinetics

A

***add in image

42
Q

Apoenzymes

A

enzymes without their cofactors

43
Q

Haloenzymes

A

enzymes with their cofactors

44
Q

Prosthetic groups

A

Tightly bound cofactors or coenzymes necessary for enzyme fxn

MCAT BIOCHEM (2 decks)

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