Chap 4: Proteins ll: Enzymes

Question 1

Enzymes

Answer 1

Catalysts involved in biochemical reactions (They are long primary structures)

Question 2

Substrate

Answer 2

Molecules that act as the reactant in an enzymatically catalyzed reaction

Question 3

Active Site

Answer 3

The location on the enzyme where the bind of the substrate occurs and catalysis occurs

Question 4

Enzyme - Substrate Binding Model

Answer 4

Lock and Key
Induced Fit

Question 5

Lock and Key

Answer 5

enzyme’s active site and the shape of the substrate molecule are complementary to one another

Question 6

Induced Fit

Answer 6

a substrate binds to an active site and both change shape slightly, creating an ideal fit for catalysis

Question 7

Kinetics

Answer 7

the branch of chemistry or biochemistry concerned with measuring and studying the rates of reactions. Study of something overtime

Question 8

Enzyme Mechanism

Answer 8

Lowers activation energy to increase reaction rate (only affects the rate of the reaction)

Question 9

Michaelis-Menten Constant

Answer 9

the amount of substrate necessary to allow an enzyme to function at half its maximal velocity

Question 10

Saturation Kinetic Curve

Answer 10

shows the relationship between substrate concentration and the reaction rate of an enzyme and shows how the kinetic constants K m and V max can be derived

Question 11

Turnover number

Answer 11

the number of reactions the enzyme can catalyze per unit of time

Question 12

Diffusion Controlled Limit

Answer 12

An occurrence when rate limiting step becomes the diffusion of enzyme and substrate together

Question 13

What do Inhibitors do

Answer 13

Prevents the generation of products
(Can be irreversible or reversible)

Question 14

Suicide Inhibitors

Answer 14

an irreversible form of enzyme inhibition that occurs when an enzyme binds a substrate analog
(Directly poisons the enzyme)

Question 15

Competitive Inhibition

Answer 15

substrate molecule is prevented from binding to the active site of an enzyme by a molecule that is very similar in structure to the substrate

• Competes with substrate (based on concentration)

Question 16

Uncompetitive Inhibition

Answer 16

Binds only to the ES complex (Enzyme-Substrate complex)
-Doesn’t compete with substrate
-Decrease Vmax

Question 17

Mixed Inhibition

Answer 17

-Binds in the presence or absence of substrate
-Combination of competitive and uncompetitive inhibitors
-Effective regardless of substrate concentration

Question 18

General Principles of Enzyme Catalyzed Reactions

Answer 18

-Enzymes bind to substrates using weak forces and orient there chemistry to occur
-Entropy (chaos) is lowered = is being put in order
-In induced fit, the enzymes bind substrates that favor the transition state

Question 19

Types of Catalysis

Answer 19

General acid-base catalysis

Metal Ion catalysis

Covalent catalysis

Question 20

General acid-base catalysis (Lysozyme)

Answer 20

*Amino acid side chain donates or accepts protons

*Polar and charged amino acids play important roles

Question 21

Metal Ion catalysis (Anhydrase)

Answer 21

Active site metal can act as a redox active center

Question 22

Covalent catalysis (Chymotrypsin)

Answer 22

-Nucleophilic or electrophilic attack on an attack on an atom results in a covalent intermediate
(Involves several cofactors)

Question 23

Enzyme Regulation

Answer 23

• Activity can be regulated by altering gene expression (DNA)
  • Sequestration of the enzyme in one compartment of the cells or one again
  • Limit the access of the enzyme to the substrate
  • Methods include:
    Covalent modification and allosteric regulation

Question 24

Covalent Modification

Answer 24

the covalent addition or removal of groups from protein through covalent bonds (thereby turning the enzyme on or off)

Question 25

Zymogens

Answer 25

inactive enzyme precursors that require proteolytic activation

Question 26

Inactive form all is needed to break a bond from the enzyme then it is activated

Answer 26

Specifically proteases moving a part of the inactive then the enzyme is active

Question 27

Proteolytic cleavage

Answer 27

an example of enzyme activation An inactive enzyme becomes active through cleavage

Question 28

Phosphorylation (addition of phosphate group)

Answer 28

* Example of protein activation * Facilitated by protein kinases * Protein kinases add phosphate groups (from ATP donor) * Phosphateses removes phosphate groups **Groups with OH group can only be phosphated for the addition of phosphates

Question 29

Allosteric Regulation

Answer 29

Increases or decreases the enzymatic activity by binding at a site other than the active site Most rapid and most direct form of regulation

Question 30

Allosteric Regulation: Inactive

Answer 30

changes the shape of the active site on the enzyme = the substrate cannot fit (inhibition)

Question 31

Allosteric Regulation: Active

Answer 31

changes the shape of the active site so it fits

Question 32

Enzyme Complex Substrate

Answer 32

Substrate and enzyme together

Question 33

Oxidoreductases

Answer 33

Catalyze reactions involving the gain or loss of electrons

Question 34

Hydrolases

Answer 34

cleave a bond with water break (bonds when introduced with water)

Question 35

Lyases

Answer 35

break double bonds using some other means than oxidation or hydrolysis

Question 36

Isomerases

Answer 36

(one molecule converts to its isomer) catalyze a rearrangement of the molecule

Question 37

Ligases

Answer 37

Joining two molecules

Question 38

Example of Acid-Base Catalysis

Answer 38

Lysozyme (natural antibiotic) (Found in egg whites, tears)

Question 39

An example of metal ion catalysis

Answer 39

Anhydrase (found in erythrocytes (rbc))

Question 40

Example of an enzyme that degrades proteins

Answer 40

Proteases (cleaves peptide bonds)

Question 41

An example of covalent catalysis

Answer 41

Chymotrypsin