Enzymatic reactions

Question 1

What is a transferase? Examples?

Answer 1

Transfer functional groups (substitution)
-Acyl transferases: transfer an acyl group
-Kinases: transfer a phosphate group
-Transaminase: transfer an amino group
-Methyl transferase: transfers a methyl group

Question 2

What is a hydrolase? Examples?

Answer 2

Breaks bonds using water (acyl subsitution).
i.e ester or amide ——-> carboxylic acid

-Lipases: hydrolysis of fats
-Esterases: hydrolysis of esters
-Glycosidase: hydrolysis of carbohydrates
-Glycosylase: hydrolysis of sugars in DNA/RNA

Question 3

What is an oxidoreductase? Examples?

Answer 3

Catalyzes REDOX reactions:

-Oxidase: transfers electrons or hydrogen
-Oxygenase: transfers an oxygen to a substrate
-Hydroxylase: catalyze the addition of hydroxyl groups
-Reductase: transfer electrons or hydrogen from a substrate
-Peroxidase: break up peroxides

Question 4

What is a lyase? Examples?

Answer 4

Catalyzes elimination reactions

(not hydrolysis or REDOX)

-Decarboxylase: remove a carboxyl
-Cyclase: cyclize ATP/GTP with loss of a phosphate group

Question 5

What is a ligase? Examples?

Answer 5

Catalyzes addition reactions

DNA ligase: joins DNA strands together (repair and replication)
Synthase: catalyzes a synthesis process

Question 6

What is isomerase? Examples?

Answer 6

Catalyzes structural shifts (intramolecular group transfer)

-Racemase: inversion of stereochemistry for substrates with one stereocenter (i.e wedge to dash)

-Epimerase: inversion of stereochemistry for substrates with multiple stereocenters

-Mutase: intramolecular group transfer

Question 7

What is a cofactor?

Answer 7

A non-protein component required to allow an enzyme to perform its role. Binds to the enzyme to promote the enzymatic process.

**Note: cofactors are typically inorganic ions - Mg, Zn, Cu, Fe, Mn, Ni, Mb or vitamins (organic).

Question 8

What are the (3) characteristics of enzymes?

Answer 8

1.) Efficiency: work better than chemical catalysts
2.) Specificity: specific for individual chemical processes
3.) Regulation: adaptive to different metabolic/environmental conditions

**Note: enzymes form hydrogen bonds with the substrates (s), not covalent bonds

Question 9

What does a catalyst do?

Answer 9

Increase the reaction rate by lowering the energy of activation.

-They do not appear in the product
-They are not consumed during the process

Question 10

Nucleophile

Answer 10

Electron rich species

(anions, heteroatoms with lone pair electrons, alkenes, alkynes)

Question 11

Electrophile

Answer 11

electron poor species

(carbocations, carbonyl group, alkenes, alkynes)

Question 12

What is spontaneity?

Answer 12

Whether or not a reaction is favorable to occur

Question 13

What is entropy?

Answer 13

Disorder. Systems that tend toward disorder is a favorable process

Question 14

What is enthalpy?

Answer 14

Energy contained within bonds. When you break a bond, it releases energy. When you form a bond, it requires energy. With enthalpy, we want to give off energy; that’s a favorable process.

Question 15

What does it mean to be non-spontaneous?

Answer 15

It means that the system REQUIRES energy. This is not favorable.

Question 16

Gibbs free energy (Delta G). What does it mean when Delta G is positive? Negative?

Answer 16

Positive = non-spontaneous reaction
Negative = spontaneous reaction

Question 17

What is a Bronsted-Lowry acid/base?

Answer 17

Acid: proton donor
Base: acceptor

Question 18

What is a Lewis acid/base?

Answer 18

Acid: electron acceptor
Base: electron donor

Question 19

What are the (3) types of substitution reaction?

Answer 19

Nucleophilic: addition of an electron rich species (nucleophile) with an electron poor species (electrophile)

Aromatic: substitution of a hydrogen on an aromatic ring with another group (not oxygen or nitrogen)

Acyl: addition of an electron rich species (nucleophile) to a CARBONYL containing group (esters, amides, carboxylic acids), sulfonate group, or phosphate group. Carbonyl group can be a C=O, S=O, or P=O

**Substitution can be thought of as ADDING and REMOVING

Question 20

What is an elimination reaction?

Answer 20

Removing a group completely from the molecule. Often (not always) results in a double bond being formed.

Question 21

What is an acid/base reaction?

Answer 21

Transfer of protons from one species to another

Question 22

What is an addition reaction?

Answer 22

Adding a group to the molecule. ALCOHOLS are commonly formed.

Question 23

What is a REDOX reaction?

Answer 23

Changing the oxidation state of a group on a molecule.
**Think about what is adding or REDUCING the number of electrons

Oxidation:
Increase the number of bonds to O or N
Decrease in the number of bonds to H

Reduction:
Decrease in the number of bonds to O or N
Increase in the number of bonds to H

Question 24

What is isomerization?

Answer 24

Rearrangemet of groups within the molecule