Enzymes

Question 1

Exergonic Rxns:

Answer 1

: Release energy; delta G is negative

Question 2

Endergonic Rxns:

Answer 2

: Require energy; delta G is positive

Question 3

Oxidoreductases:

Answer 3

: REDOX reactions that involve the transfer of e-

Question 4

Transferases:

Answer 4

Move a functional group from one molecule to another

Question 5

Hydrolases:

Answer 5

Catalyze cleavage with the addition of H2O

Question 6

Lyases

Answer 6

Catalyze cleavage without the addition of H2O and
without the transfer of e-
. The reverse reaction
(synthesis) is often more important biologically.

Question 7

Isomerases

Answer 7

Catalyze the interconversion of isomers, including both
constitutional isomers and stereoisomers.

Question 8

Ligases

Answer 8

Join two large biomolecules, often of the same type.

Question 9

Lipases:

Answer 9

Catalyze the hydrolysis of fats. Dietary fats are broken
down into fatty acids and glycerol or other alcohols.

Question 10

Kinases:

Answer 10

ADD a phosphate group. A type of transferase

Question 11

Phosphatases:

Answer 11

: REMOVE a phosphate group. A type of transferase

Question 12

Phosphorylases:

Answer 12

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

Question 13

Saturation kinetics

Answer 13

As the substrate concentration increases the reaction rate with increase until a maximum value is reached

Question 14

Michaelis menten plot

Answer 14

Hyperbolic curve

Question 15

Michaelis menten lineweaver burk plot

Answer 15

Line

Question 16

What is the km?

Answer 16

The substrate concentration when the enzyme runs half of its Vmax

Question 17

Vmax

Answer 17

The maximum rate at which an enzyme can catalyze a
reaction. This is when all enzyme active sites are
saturated with substrate.

Question 18

Michaelis Menten equation

Answer 18

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

Question 19

Cooperative enzyme graph

Answer 19

Sigmoidal curve because of the change in activity with substrate binding

Question 20

Mechanism of Enzyme Activity

Answer 20

Enzymes act by stabilizing the transition state, providing a favorable
microenvironment, or bonding with the substrate molecules.

Question 21

Active Site

Answer 21

The site of catalysis

Question 22

Lock & Key Theory

Answer 22

The enzyme and substrate are exactly complementary
and fit together like a key into a lock.

Question 23

Induced Fit Theory:

Answer 23

The enzyme and substrate undergo conformational
changes to interact fully

Question 24

Cofactors:

Answer 24

Metal cation that is required by some enzymes

Question 25

Coenzyme

Answer 25

Organic molecule that is required by some enzymes

Question 26

Properties that effect enzymes

Answer 26

Temperature and pH can denature proteins and salinity can impact the action of enzymes

Question 27

Feedback Inhibition:

Answer 27

An enzyme is inhibited by high levels of a product
from later in the same pathway.

Question 28

Reversible
Inhibition:

Answer 28

The ability to replace the inhibitor with a compound
of greater affinity or to remove it using mild
laboratory treatment

Question 29

Where do competitive inhibitors bind?

Answer 29

Active site

Question 30

How is the Vmax and Km affected by a competitive inhibitor?

Answer 30

Vmax is unchanged and Km increases

Question 31

What does a lineweaver burk graph look like for competitive inhibitors?

Answer 31

The y intercept is the same but the competitive inhibitor has a steeper slope

Question 32

Competitive
Inhibition:

Answer 32

When the inhibitor is similar to the substrate and
binds at the active site, blocking the substrate from
binding. Can be overcome by adding more substrate.
Vmax is unchanged, Km increases.

Question 33

Uncompetitive
Inhibition definition and its effect on vmax and km

Answer 33

When the inhibitor binds only with the enzyme substrate complex. Vmax and Km both decrease.

Question 34

Noncompetitive inhibition definition and its effects on both the vmax and the km

Answer 34

When the inhibitor binds with equal affinity to the
enzyme and the enzyme-substrate complex. Vmax
decreases, Km is unchanged.

Question 35

What does a lineweaver burk graph look like for uncompetitive inhibition?

Answer 35

Question 36

Lineweaver burk noncompetitive inhibition

Answer 36

Question 37

Mixed Inhibition

Answer 37

When the inhibitor binds with unequal affinity to the enzyme and the enzyme-complex. Vmax decreases, Km is increased or decreased depending on if the inhibitor has a higher affinity for the enzyme or enzyme-substrate complex.

Question 38

Irreversible Inhibition

Answer 38

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

Question 39

Suicide Inhibitor

Answer 39

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

Question 40

Allosteric Effecter:

Answer 40

: Binds at the allosteric site and induces a change in the conformation of the enzyme so the substrate can no longer bind to the active site. Displays cooperativity, so it does not obey Michaelis-Menten kinetic

Question 41

Positive Effectors

Answer 41

Exert a positive effect, increase enzyme activity

Question 42

Negative effectors

Answer 42

Exert a negative effect and decrease activity

Question 43

Homotropic Effector:

Answer 43

An allosteric regulator that IS ALSO the substrate. Ex: O2 is a homotropic allosteric regulator of hemoglobin.

Question 44

Heterotropic Effector

Answer 44

An allosteric regulator molecule that is DIFFERENT from the substrate.

Question 45

Phosphorylation:

Answer 45

Covalent modification with phosphate

Question 46

Catabolism

Answer 46

Phosphorylated = active

Question 47

Anabolism

Answer 47

Phosphorylated = inactive

Question 48

Glycosylation

Answer 48

Covalent modification with carbohydrate

Question 49

Zymogens:

Answer 49

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