Chapter 4: 4.3 Enzymes

Question 1

State:

Function of enzymes

Answer 1

Drastically increases rates of reactions, allowing cellular function (and more specifically, metabolism) to occur

Question 2

Enzymes are highly specific in their ———- (even showing ——————)

Answer 2

• Substrates
• Stereo-specificity

Question 3

How do enzymes increase reaction rate?

Answer 3

Stabilization of the transition state (lowering the energy)

Question 4

True or False:

Each enzyme has a specific substrate and active site

Answer 4

True

Question 5

How many classes of enzymes are there?

Answer 5

6

Question 6

List:

The 6 classes of enzymes

Answer 6

1. Oxidoreductases
2. Transferases
3. Hydrolases
4. Lyases
5. Isomerases
6. Ligases

Question 7

State:

Function of oxidoreductases

Answer 7

Catalyzes oxidation-reduction reactions

Question 8

What are names of oxidoreductases?

Answer 8

Oxidases, dehydrogenases, reductases

Question 9

What happens in an oxidation-reduction reaction?

Answer 9

• One substrate is oxidized (loses electrons)
• One substrate is reduced (gains electrons)

Question 10

In redox reactions:

What is the method to keep track of where electrons are going?

Answer 10

Follow the hydrogen atoms, typically:
* Oxidized molecules lose hydrogen atoms
* Reduced molecules gain hydrogen atoms

Question 11

State:

Function of transferases

Answer 11

Group transfer reactions

Question 12

1. What are kinases?
2. What is the process that they perform called?

Answer 12

1. Transfer phosphate groups
2. Phosphorylation

Question 13

State:

Function of hydrolases

Answer 13

Catalyzes hydrolysis reactions

Question 14

What is a hydrolysis reaction?

Answer 14

Breaking apart molecules with water

Question 15

True or False:

Hydrolases are the largest group of enzymes

Answer 15

True

Question 16

What enzymes are included in the hydrolase group? (4)

Answer 16

• Proteases
• Lipases
• Nucleases
• Esterases

Question 17

State:

Function of lyases

Answer 17

Addition of groups to double bonds or removal of groups to form double bonds

Question 18

What are lyases also referred to as?

Answer 18

Synthases (perform addition reactions)

Question 19

Give a WIZEPREP example of a(n):

1. Oxidoreductase
2. Transferase
3. Hydrolase
4. Lyase
5. Isomerase
6. Ligase

Answer 19

1. Xanthine dehydrogenase
2. Transketolase
3. Phloretin hydrolase
4. Methylisocitrate lyase
5. Isopentenyl pyrophosphate isomerase
6. Synthetase

Question 20

State:

Function of isomerases

Answer 20

Transfer groups within molecules (create isomers)

Question 21

What enzyme type is found in the isomerase group?

Answer 21

Mutases

Question 22

State:

Function of ligases

Answer 22

Joins two molecules through the use of ATP (energy source)

Question 23

Define:

Enzyme Active Site

Answer 23

A pocket on the enzyme that provides a specific environment, within which a reaction can occur more rapidly

Question 24

List:

Levels of specificity of an enzyme active site

Answer 24

1. High degree of specificity
2. Function group specificity
3. Broader specificity

Question 25

# Explain: High degree of specificity (Enzyme active site)

Answer 25

Only acts properly on only one substrate

Question 26

# Explain: Functional group specificity (Enzyme active site)

Answer 26

Acts on multiple substrates with a key functional group

Question 27

# Explain: Broader specificity (Enzyme active site)

Answer 27

Acts on substrates with the same molecular "scaffold"

Question 28

What is the "lock and key" in an enzyme?

Answer 28

* Lock: Shape of active site * Key: Substrate The shape of the active site is complementary to the substrate

Question 29

# True or False: The enzyme cannot change shape to accept a substrate

Answer 29

False, it is its own microenvironment and can change to accept a substrate

Question 30

# Define: Nucleophiles

Answer 30

Electron rich species that have an affinity for positively charged (nucleus)

Question 31

# Define: Electrophiles

Answer 31

Electron poor species that have an affinity for electron rich atoms

Question 32

# Describe: Nucleophilic substitution

Answer 32

1. Electron-rich chemical species (nucleophile) replaces functional group 2. The nucleophile replaces an electrophile and leaving the functional group (known as the substrate)

Question 33

# Define: Proximity Effect

Answer 33

Brings components close together, increasing the chance of completing the reaction

Question 34

Transition states are --------- and --------

Answer 34

1. Fleeting 2. Unstable

Question 35

How is stabilization of transition state achieved?

Answer 35

The enzyme binds to the transition state and stabilizes it

Question 36

# Describe: Acid-Base Catalysis

Answer 36

Electrons are either transferred from an acid catalyst to the substrate or from the substrate to a base catalyst

Question 37

# State the role of the functional group for: Aspartate

Answer 37

Cation binding; proton transfer

Question 38

# State the role of the functional group for: Glutamate

Answer 38

Cation binding; proton transfer

Question 39

# State the role of the functional group for: Histidine

Answer 39

Proton transfer

Question 40

# State the role of the functional group for: Cysteine

Answer 40

Covalent binding of acyl groups

Question 41

# State the role of the functional group for: Tyrosine

Answer 41

H-bonding to ligands

Question 42

# State the role of the functional group for: Lysine

Answer 42

Anion binding; proton transfer

Question 43

# State the role of the functional group for: Arginine

Answer 43

Anion binding

Question 44

# State the role of the functional group for: Serine

Answer 44

Covalent binding of acyl groups

Question 45

What can cofactors be?

Answer 45

1. Essential Ions 2. Coenzymes

Question 46

# For essential ion cofactors: What are essential ions?

Answer 46

Mg2+, Ca2+, Fe2+, Co+

Question 47

# For essential ion cofactors: What are the two types?

Answer 47

1. Activator ions: Closely bound 2. Metal ions: Tightly bound

Question 48

# For coenzyme cofactors: What are coenzymes?

Answer 48

Organic compounds

Question 49

# For coenzyme cofactors: What are the two types?

Answer 49

1. Cosubstrates: Loosely bound 2. Prosthetic groups: Tightly bound

Question 50

What is NAD+?

Answer 50

Nicotinamide Adenine Dinucleotide * Coenzyme * Reduced form is NADH

Question 51

What is NADP+?

Answer 51

Nicotinamide Adenine Dinucleotide Phosphate * Coenzyme * Reduced form is NADPH

Question 52

What is FAD2+?

Answer 52

Flavin Adenine Dinucleotide * Coenzyme * Reduced form is FADH2

Question 53

What is ATP?

Answer 53

Adenosine triphosphate * Coenzyme

Question 54

# List: Forms of Enzyme Regulation

Answer 54

1. Substrate Availability 2. Covalent Modifications 3. Allosteric Control 4. Zymogens, Proenzymes

Question 55

How does Substrate Availability regulates enzymes?

Answer 55

Enzyme can only catalyze reaction if there is substrate present to act on

Question 56

How do Covalent Modifications regulate enzymes?

Answer 56

Enzyme induced chemical changes to enzymes that can activate or de-activate enzymes

Question 57

How does Allosteric Control regulate enzymes?

Answer 57

A regulatory molecule binds to a site on the enzyme, separate form the active site, and alters enzyme shape and function * Feedback inhibition

Question 58

What are Zymogens and Proenzymes?

Answer 58

Inactive precursors of enzymes

Question 59

Give an example of zymogens/proenzymes

Answer 59

Digestive enzymes (activate when expelled from cell) * Trypsinogen to trypsin * Proelastase to elastase * Chymotrypsinogen to Chymotrypsin * Etc.