Enzymes 1

Question 1

What 2 macromolecules are enzymes composed of?

Answer 1

Proteins (most enzymes) and RNA (ribozymes)

Question 2

What are artificial enzymes called?

Answer 2

Abzymes

Question 3

Enzymes that act as catalytic Ribozymes do what?

Answer 3

Lower activation energy without being consumed.

Mediate the transformation of energy.

Question 4

Why do enzymes exhibit a high degree of specificity?

Answer 4

They are highly specific due to their active sites fitting the structure of their particular ligand/substrate

Question 5

Proteolytic enzymes tend to catalyze what kind of reactions?

Answer 5

They hydrolyze peptide bonds and ester bonds (become an alcohol and an acid)

Question 6

What are the two main classes of cofactors?

Answer 6

Coenzymes (organic molecules derived from vitamins) and Metals

Question 7

What is a haloenzyme?

Answer 7

A complex enzyme consisting of an enzyme portion and coenzyme.

Question 8

What are the 2 major portions of a haloenzyme called?

Answer 8

The Apoenzyme is the protein component and the Coenzyme is the non-protein component.

Question 9

How is bonding to an Apoenzymes different from a Metalloenzyme bond?

Answer 9

Bonding to an Apoenzyme is either via a covalent bond (prosthetic group) or non-covalent,

Metalloenzymes require a tightly bound metal ion.

Question 10

Main clinical symptoms of dietary vitamin insufficiency generally arise from what?

Answer 10

The malfunction of enzymes. The lack of vitamins would lead to a lack of cofactor. This means enzymes are not functional enough to maintain homeostasis.

Question 11

Describe the role of a coenzyme in detail

Answer 11

A cofactor is effectively a transporter of chemical groups from one reactant to another. They participate in catalysis by binding the active site and donating their group. (think NADH to NAD+ in glycolysis)

Question 12

What do the oxidoreductase class of enzymes accomplish?

Answer 12

Work on many group to add or remove hydrogen ions (oxidation/reduction reactions).

Question 13

What do Transferases do?

Answer 13

Transfer functional groups between donor and acceptor molecules. Kinases are specialized transferases that regulate metabolism by transferring phosphate from ATP to other molecules

Question 14

What do hydrolases do?

Answer 14

Add water across a bond to break it

Question 15

What do lyases do?

Answer 15

Add water, ammonia or carbon dioxide across double bonds, or remove these groups to produce double bonds

Question 16

What do isomerases do?

Answer 16

Carry out many kinds of isomerization: L to D isomerization, mutase reactions (shifts of chemical groups)

Intramolecular Rearrangement

Question 17

What do ligases do?

Answer 17

Catalyze reactions in which two chemical groups are joined or ligated using energy from ATP (lengthen DNA)

Question 18

Describe the induced-fit-model

Answer 18

Initial interactions between enzyme and substrate is weak.

Weak interactions rapidly induce conformational changes in enzyme that strengthen binding and bring catalytic sites close to substrate bonds to be altered.

Post binding, mechanisms of catalysis generate transition state complexes and reaction products.

Question 19

What is a transition state?

Answer 19

A form during catalytic reactions that is no longer substrate, but not yet product. Energy used to form this is activation energy.

Question 20

What is binding energy, and when is it at its greatest?

Answer 20

It is free energy released upon interaction of the enzyme and substrate. It is at its greatest when the enzyme interacts with the transition state.

Question 21

Describe Delta G in relation to enzymatic reactions

Answer 21

It represents free energy capable of doing work.

It describes the relations between the enzyme catalysis of a reaction, the thermodynamics of the reaction, and the formation of the transition state

Describes spontaneity NOT RATE of reaction

Question 22

What is the relationship between substrate concentration and reaction rate?

Answer 22

As substrate concentration [S] increases, rate of the reaction [Vm] approaches Vmax.

Question 23

Describe catalysis involving Acids and Bases

Answer 23

Acids donate protons and bases receive protons causing catalytic events initiated by a strain mechanism

Question 24

Describe Covalent catalysis

Answer 24

Substrate is oriented to active sites on the enzyme in such a way that a covalent intermediate forms between the enzyme and the substrate.

Question 25

Describe Metal Ion catalysis (Electrostatic catalysis)

Answer 25

Metal ions bind to substrate to orient them: mediate oxidation-reduction reactions; electrostatically stabilize or shield negative charges; and often act similar to a proton, or polarize water to generate OH

Question 26

Describe catalysis by Proximity and Orientation

Answer 26

Enzyme-substrate interactions orient reactive groups and bring them into proximity with one another for catalysis.