Exp 3: Enzymes

Question 1

Identify the term:
biological catalysts that accelerate the rate of biochemical reactions

Answer 1

enzymes

Question 2

Identify the mechanism:
how enzyme accelerates the reaction rate

Answer 2

by reducing free energy activation
( a factor of up to 10^20 over an uncatalyzed reaction)

Question 3

T/F:
an enzyme is regenerated after the reaction

Answer 3

true

Question 4

T/F:
an enzyme changes the equilibrium of the reaction

Answer 4

false;
does not change

Question 5

Identify the term:
suffix to identify enzyme

Answer 5

Name+ase

Question 6

Enumerate:
chemical nature of enzymes

Answer 6

1. majority are proteins
2. some are RNA: ribozymes

Question 7

T/F:
enzymes function at MILDER reaction conditions

Answer 7

true

Question 8

T/F:
enzymes are efficient in catalyzing LOWER reaction rate than a chemical catalyst

Answer 8

false;
higher

Question 9

T/F:
enzymes have LOW reaction specificity

Answer 9

false;
greater reaction specificity
(some catalyze the reaction of only one stereoisomer; others catalyze a family of similar reactions)

Question 10

Identify the term:
biomolecule acted upon by the enzyme

Answer 10

substrate

Question 11

Identify the term:
specific region of the enzyme that creates a 3D surface complementary to the substrate

Answer 11

active site

Question 12

Enumerate:
6 classes of enzymes

Answer 12

EC 1: oxidoreductases
EC 2: transferases
EC 3: hydrolases
EC 4:lyases
EC 5: isomerases
EC 6: ligases

Question 13

Identify the enzyme class
(based on the type of reaction catalyzed):
1. redox reactions
2. transfer of electrons
(hydride ions or H atoms)

Answer 13

oxidoreductases

Question 14

Identify the enzyme class
(based on the type of reaction catalyzed):
transfer of a group from one substrate (donor) to another (acceptor)

Answer 14

transferases

Question 15

Identify the enzyme class
(based on the type of reaction catalyzed):
hydrolysis (addition of H2O) of C-C, C-O, C-N and bonds like phosphoanhydride

Answer 15

hydrolases

Question 16

Identify the enzyme class
(based on the type of reaction catalyzed):
addition (other than H2O) of groups to double bonds or removal of groups to form double bonds

Answer 16

lyases

Question 17

Identify the enzyme class
(based on the type of reaction catalyzed):
1. convert the substrate into its isomer
2. transfer of groups within molecules to form isomers

Answer 17

isomerases

Question 18

Identify the enzyme class
(based on the type of reaction catalyzed):
joining 2 molecules with the hydrolysis of ATP

Answer 18

ligases

Question 19

Enumerate:
subclasses of oxidoreductases

Answer 19

1. oxidases
2. oxygenase
3. hydroxylase/ monooxygenase
4. dehydrogenase
5. reductase

Question 20

Identify which subclass of oxidoreductases:
introduction of one oxygen atom from a molecule of O2

Answer 20

oxidases

Question 21

Identify which subclass of oxidoreductases:
introduction of both atoms of the O2 into the substrate

Answer 21

oxygenase

Question 22

Identify which subclass of oxidoreductases:
1 atom of O2 is introduced to the substrate and the other atom forms water

Answer 22

hydroxylase/ monooxygenase

Question 23

Identify which subclass of oxidoreductases:
redox where electrons are removed from the substrate

Answer 23

dehydrogenase

Question 24

Identify which subclass of oxidoreductases:
e- (with accompanying H+) are added to the substrate

Answer 24

reductase

Question 25

Identify the enzyme class
(based on the type of reaction catalyzed):
cleavage of chemical bonds by the transfer of water

Answer 25

hydrolase

Question 26

Enumerate:
classifications of isomerase

Answer 26

1. epimerase
2. isomerase
3. mutase

Question 27

Identify which type of isomerase:
ribulose 5-phosphate _________

Answer 27

epimerase

Question 28

Identify which type of isomerase:
triose phosphate __________

Answer 28

isomerase

Question 29

Identify which type of isomerase:
change in position of a substituent

Answer 29

mutase

Question 30

Identify other term:
ligase

Answer 30

also known as synthetases

Question 31

Identify:
new classification of enzyme

Answer 31

translocases (EC 7)

Question 32

Identify the enzyme class
(based on the reaction catalyzed):
assists movement of another molecule across a cell membrane

Answer 32

translocases

Question 33

Enumerate:
factors affecting enzyme activity

Answer 33

1. pH
2. temperature
3. enzyme concentration [E]
4. substrate concentration [S]
5. inhibitor
6. cofactor

Question 34

Identify:
pH at which an enzyme exhibits maximum activity (achieves Vmax/ maximum reaction rate)

Answer 34

optimal pH

Question 35

Identify the degree of change in pH:
alters the charge of acidic and basic amino acid residues found in active site

Answer 35

slight change in pH

Question 36

Identify the degree of change in pH:
denatures enzyme irreversibly; loss of catalytic activity

Answer 36

extreme pH
(too acidic/ basic)

Question 37

Identify:
temperature at which an enzyme exhibits maximum activity

Answer 37

optimal temperature

Question 38

Enumerate:
what happens at ↓ temp

Answer 38

↓ KE = less molecular collisions = ↓ rxn rate

Question 39

Enumerate:
what happens beyond optimum T

Answer 39

1. disrupts 3° structure of enzyme
2. substrate may not fit the active site
3. impedes catalytic reaction

Question 40

Identify:
how E conformation is altered (may be irreversible)

Answer 40

by change in temperature

Question 41

Identify the enzyme:
yeast-derived enzyme

Answer 41

invertase

Question 42

Identify:
official name of invertase

Answer 42

β-fructofuranosidase (EC 3.2.1.26)

Question 43

Determine:
hydrolysis of invertase

Answer 43

hydrolyzes α1→β2 glycosidic bond in sucrose

Question 44

Identify:
invertase’s enzyme class

Answer 44

hydrolase
(catalyzing hydrolysis of the terminal non-reducing β-fructofuranosidase residues)

Question 45

Fill in the blanks:
Invertase splits sucrose to _________ and __________.

Answer 45

glucose
fructose

Question 46

Identify the method:
used to monitor enzyme activity

Answer 46

dinitrosalicylic acid method

Question 47

Identify:
principle involved in dinitrosalicylic acid method

Answer 47

3,5-dinitrosalicylic acid (DNS) reacts with reducing sugars to form 3-amino-5-nitrosalicylic acid (ANS)

Question 48

T/F:
DNS reacts with sucrose (non-reducing sugar)

Answer 48

false;
does not react

Question 49

Identify:
DNS color
new color formed

Answer 49

DNS: yellow
upon reaction: red

Question 50

Identify:
red coloration indication

Answer 50

↑ red coloration = ↑ [glucose & fructose] = ↑ invertase activity