Enzymes

Question 1

Characteristics of enzymes

Answer 1

➢ Lower the activation energy (Ea)
➢ Increase the rate of reaction
➢ Activity lost if denatured
➢ May contain cofactors such as metal ions or
organic (vitamins)

Question 2

All catalysts share 3 basic properties:

Answer 2

a. Increases reaction rate by lowering Ea required.
b. Forms reversible complexes with substrate molecules
c. Changes the RATE at which the equilibrium is achieved, not the POSITION of the equilibrium

Question 3

Have high substrate affinity and specificity.
Also, reusable. They are not
used up in the reaction.

Answer 3

Enzymes

Question 4

usually a groove or
pocket that
accommodates the
intended substrate(s)
with high affinity

Answer 4

ACTIVE SITE

Question 5

a molecule acted upon
by an enzyme

Answer 5

SUBSTRATE

Question 6

binding that involves hydrogen
bonds, ionic bonds or
both, and are readily reversible

Answer 6

SUBSTRATE BINDING

Question 7

Reactants need to
reach an intermediate
chemical stage called
the and overcome the EA barrier for
needed reactions to
occur.

Answer 7

transition state.

Question 8

what overcome
the activation energy
barrier.

Answer 8

Catalysts

Question 9

what do catalyst do to speed up reaction

Answer 9

lower activation energy

Question 10

• catalyzes Oxidation-reduction reactions
• catalyzed the Transfer of functional group of molecules
• catalyzed the Hydrolytic cleavage of molecules
• catalyzed the Removal/Addition of a group of atoms to/from a double bond
• catalyzed the Rearrangement of atoms within a molecule
• catalyzed the Joining of 2 molecules to form a single molecule with ATP hydrolysis

Answer 10

• Oxidoreductases
• Transferases
• Hydrolases
• Lyases
• Isomerases
• Ligases

Question 11

transfer amino groups

Answer 11

transaminases –

Question 12

transfer phosphate groups

Answer 12

kinases

Question 13

hydrolyze peptide bonds

Answer 13

proteases

Question 14

hydrolyze lipid ester bonds

Answer 14

lipases

Question 15

catalyzed the cleavage of C-C, C-O, C-N,
and other bonds by elimination, leaving
double bonds, and also adding groups to
double bonds.

Answer 15

Lyase

Question 16

catalyze the movement of ions or
molecules across membranes or
their separation within
membranes.

Answer 16

Translocases

Question 17

Series of four numbers that denote the class,
subclasses, sub-subclasses, and individual
entries to describe a particular enzyme.

Answer 17

International Commission on
Enzymes

Question 18

The lock and key analogy is that the enzyme
is the lock and the substrate is the key.

Answer 18

lock and key model

Question 19

Enzyme structure flexible, not rigid
Enzyme and active site adjust shape to
bind substrate

Answer 19

Induced fit model

Question 20

Enumerate the catalytic process

Answer 20

STEP 1:
The random collision of a substrate molecule
with the active site results in it binding there
STEP 2:
Substrate binding induces a conformational
change that tightens the fit, facilitating the
conversion of substrate into products
STEP 3:
The products are then released from the active
site
STEP 4:
The enzyme molecule returns to the original
conformation with the active site available for
another molecule of substrate

Question 21

Factors Affecting Enzyme
Action

Answer 21

1. Environmental Conditions
2. Cofactors And Coenzymes
3. Enzyme Inhibitors

Question 22

Different environmental condition that affects enzyme

Answer 22

Temperature
Substrate concentration
pH

Question 23

Enzyme increases with temperature until it reaches the

Answer 23

Optimum temperature

Question 24

Optimum temp in Human enzyme and Bacterial enzyme

Answer 24

37°C, 75°C

Question 25

Increasing _________ concentration increases the rate of reaction

Answer 25

substrate

Question 26

When does the maximum activity reached when we add substrate concentration to increase the rate of reaction?

Answer 26

when all of enzyme combines with substrate

Question 27

Optimum pH is

Answer 27

7

Question 28

Substances that are sometimes needed for proper enzymatic activity, often because they function as electron acceptors

Answer 28

Cofactors and coenzymes

Question 29

usually metal ions or small organic molecules called coenzymes.

Answer 29

Prosthetic enzymes

Question 30

small molecules needed in catalytic activity

Answer 30

Cofactors

Question 31

derived in vitamins

Answer 31

coenzymes

Question 32

In the oxygen circulation through the blood, what is the cofactor used?

Answer 32

Iron

Question 33

- Molecules which slow down or prevent an enzyme reaction - Cause a loss of catalytic activity - Change the protein structure of an enzyme

Answer 33

Inhibitors

Question 34

Inhibitors bind the enzyme very tightly; generally form covalent bonds causing permanent loss of catalytic activity and are generally toxic to cells

Answer 34

Irreversible inhibitors

Question 35

inhibitors bind enzymes non covalently; can dissociate with the enzyme

Answer 35

Reversible inhibitors

Question 36

Inhibitor that binds at the active site

Answer 36

Competitive

Question 37

Inhibitor that binds at another site on enzyme

Answer 37

Noncompetitive

Question 38

As substrate concentration increases in competitive inhibition, the substrate molecules outnumber the inhibitor so

Answer 38

the reaction rate reaches the maximum

Question 39

A high substrate concentration is added in noncompetitive inhibition, this result to

Answer 39

no change in the reaction rate

Question 40

describes the quantitative aspects of enzyme catalysis and the rate of substrate conversion into products

Answer 40

enzyme kinetics

Question 41

are measured over a brief time, during which the substrate concentration has not yet decreased enough to affect the rate of reaction.

Answer 41

initial reaction rates

Question 42

the rate of change in product concentration per unit time

Answer 42

Initial reaction velocity (v)

Question 43

Initial reaction velocity (v), the rate of change in product concentration per unit time, depends on the

Answer 43

Substrate concentration [S]

Question 44

The Michaelis-Menten equation revealed that the initial velocity of the reaction is roughly proportional to [S] at ___

Answer 44

at very low [S],

Question 45

The Michaelis-Menten equation revealed that the initial velocity of the reaction is independent of variation in [S]. This state happens at

Answer 45

At very high [S],

Question 46

is the velocity at saturating substrate concentrations

Answer 46

Vmax

Question 47

Michaelis-Menten equation

Answer 47

v = Vmax [S] / KM + [S]

Question 48

The half of Vmax is

Answer 48

Km

Question 49

Km is a useful indicator of for the

Answer 49

affinity of an enzyme for the substrate

Question 50

Note that an enzyme with a low Km has a ____ affinity for the substrate

Answer 50

high

Question 51

is an upper limit determined by the time required for the actual catalytic reaction and how many enzyme molecules are present.

Answer 51

Vmax

Question 52

The only way to increase Vmax is to

Answer 52

increase enzyme concentration.

Question 53

x-axis and y-axis in Michaelis graph

Answer 53

x = initial rate, V y = substrate concen

Question 54

The ______the Km value for a given enzyme and substrate, the lower the [S] range in which the enzyme is effective.

Answer 54

lower

Question 55

a measure of the potential maximum rate of the reaction

Answer 55

Vmax

Question 56

x-axis and y-axis in Lineweaver-Burk plot

Answer 56

x = 1/Vo y = 1/[S]

Question 57

Visualize the Lineweaver-Burk plot, point out the location of -1/Km, Km/Vmax, and Vmax

Answer 57

use your imagination gurl

Question 58

In competitive inhibition, what happen to Km and Vmax

Answer 58

Vmax is unaffected KM is increased

Question 59

In noncompetitive inhibition, what happen to Km and Vmax

Answer 59

Vmax is decreased KM is unaffected

Question 60

In uncompetitive inhibition, what happen to Km and Vmax

Answer 60

Vmax is decreased KM is decreased

Question 61

Once slope and y-intercept is calculated, what to solved first and how? What to do next?

Answer 61

Solved for Vmax = 1/y-intercept Then, Solved for Km = slope/Vmax