Enzymes

Question 1

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.

Answer 1

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.

Question 2

Ligase

Answer 2

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

Question 3

Isomerase

Answer 3

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

Question 4

Lyase

Answer 4

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

Question 5

Hydrolase

Answer 5

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

Question 6

Oxidoreductase

Answer 6

Redox reactions (transfer of electrons)

Question 7

Transferase

Answer 7

Movement of a fxl group from one molecule to another

Question 8

Lipase

Answer 8

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

Question 9

Kinases

Answer 9

Add a phosphate group. Type of transferase.

Question 10

Phosphatases

Answer 10

Remove a phosphate group. Type of transferase.

Question 11

Phosphorylases

Answer 11

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

Question 12

Exergonic Rxns

Answer 12

Release Energy, - ΔG

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Question 13

Endergonic Rxns

Answer 13

Require Energy, + ΔG

Question 14

As [S] increases,

Answer 14

Rate of the reaction increases until a maximum value is reached

Question 15

Km

Answer 15

[S] at which an enzyme runs at half Vmax

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

Question 16

Vmax

Answer 16

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

Question 17

Cooperative Enzymes

Answer 17

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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Question 18

M-M plot

Answer 18

Hyperbolic curve

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Question 19

Lineweaver-Burk plot

Answer 19

Line

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Question 20

Competitive Inhibition

Answer 20

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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Question 21

Noncompetitive Inhibition

Answer 21

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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Question 22

Mixed Inhibition

Answer 22

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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Question 23

Uncompetitive Inhibition

Answer 23

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

Reversible Inhibition

Answer 24

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

Question 25

Irreversible Inhibition

Answer 25

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

Question 26

High Km

Answer 26

Low affinity

Question 27

Low Km

Answer 27

High affinity

Question 28

suicide inhibitor

Answer 28

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

Question 29

Feedback inhibition

Answer 29

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

Question 30

Allosteric Effector

Answer 30

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).

Question 31

Homotropic Effector

Answer 31

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

Question 32

Heterotropic Effector

Answer 32

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

Question 33

Effects of local conditions on enzymes | temperature, pH, and salinity

Answer 33

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

Question 34

Lock and Key Theory

Answer 34

E and S are exactly complementary and fit together like a key into a lock ***add in image

Question 35

Induced Fit Theory

Answer 35

E and S undergo conformational changed to interact fully | ***add image

Question 36

Cofactors

Answer 36

Metal cation that is required by some enzymes

Question 37

Coenzyme

Answer 37

Organic molecule that is required by some enzymes

Question 38

Phosphorylation

Answer 38

- covalent modification with phosphate - can alter the activity or selectivity of the enzyme - Catabolism: Phosphorylated = active - Anabolism: Phosphorylated = inactive

Question 39

Glycosylation

Answer 39

- covalent modification with carb | - can alter the activity or selectivity of the enzyme

Question 40

Zymogens

Answer 40

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

Question 41

Reaction Scheme for M-M kinetics

Answer 41

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Question 42

Apoenzymes

Answer 42

enzymes without their cofactors

Question 43

Haloenzymes

Answer 43

enzymes with their cofactors

Question 44

Prosthetic groups

Answer 44

Tightly bound cofactors or coenzymes necessary for enzyme fxn