Chapter 20

Question 1

What are Catalysts?

Answer 1

Catalysts are agents that accelerate the rate of a reaction without being consumed. They can be made of metals, polymers, and proteins.

Question 2

What is a Substrate?

Answer 2

The compound on which the enzyme works.

Question 3

What is the Active Site?

Answer 3

A 3D cavity in the enzyme that can accommodate the substrate.

Question 4

What is Inhibition?

Answer 4

A process that makes the enzyme less active. 2 types: Competitive and Noncompetitive.

Question 5

Explain Competitive Inhibitors.

Answer 5

Inhibitors that bind directly to the active site.

Question 6

Explain Noncompetitive Inhibitors.

Answer 6

Inhibitors that do not bind to the active site but still inhibits the activity of the enzyme.

Question 7

What are Cofactors?

Answer 7

Nonprotein portions of the enzyme necessary for its catalytic function.

Question 8

What is a Coenzyme?

Answer 8

An organic cofactor.

Question 9

What is a Apoenzyme?

Answer 9

A enzyme without a cofactor

Question 10

Explain how to name Enzymes.

Answer 10

• Names is based on what it reacts with and how it reacts.
• Add -ase to the end of the name.

Question 11

Explain Oxidoreductase.

Answer 11

Classification of Enzymes that catalyze and oxidation/reduction reaction,

Question 12

Explain Transferase.

Answer 12

Classification of Enzymes that transfers a functional group.

Question 13

Explain Hydrolase.

Answer 13

Classification of Enzymes that causes a hydrolysis reaction.

Question 14

Explain Lyase.

Answer 14

Classification of Enzymes that breaks C-O, C-C, or C-N bonds.

Question 15

Explain Isomerase.

Answer 15

Classification of Enzymes that rearranges functional groups.

Question 16

Explain Ligase.

Answer 16

Classification of Enzymes that joins two molecules.

Question 17

What are the 2 component of the Active Site. Explain them.

Answer 17

Binding Site: area that holds the substrate in the proper place. Enzymes use nonpolar covalent interactions with amino acids side chains to hold the substrate.

Catalytic Site: where the reaction actually occurs.

Question 18

Explain the Activation Energy Barrier.

Answer 18

Activation Energy is the minimum amount of energy required for a chemical reaction to start by allowing reactant particles to collide with enough force to break bonds and form new ones.
- For all reactions to occur, you must get over the Activation Energy Barrier.

Question 19

What is the formula for Enzyme Reactions?

Answer 19

Question 20

Explain the Lock and Key Model.

Answer 20

• Molecules are the ‘key” that fit in enzymes the ‘lock”
• Assumes that enzymes are rigid
• Active site is restricted to only those molecules that can fit into the site.

Question 21

Explain the Induced-Fit Model.

Answer 21

• Assumes that enzymes are flexible
• Changes occur to the shape of the active site to accommodate the substrate
• Like fitting a hand into a glove

Question 22

T/F: Enzymes will only react with molecules that are specific for that enzyme.

Answer 22

True

Question 23

Explain Absolute Specificity.

Answer 23

Type of Enzyme Specificity that catalyzes reactions with only one substrate
- Lactase only reacts with lactose

Question 24

Explain Group Specificity.

Answer 24

Type of Enzyme Specificity that catalyzes reactions with a collection of molecules that contain the same functional group
- Carboxypeptidase which hydrolyzes peripheral peptide bonds at the carboxyl terminus

Question 25

Explain Linkage Specificity.

Answer 25

Type of Enzyme Specificity that catalyzes the formation or breakage of certain bond in a molecule

Question 26

Explain Stereochemical Specificity.

Answer 26

Type of Enzyme Specificity that enzymes can distinguish one enantiomer from another

Question 27

In what ways can Enzyme Activity be affected?

Answer 27

The activity of an enzyme describes how fast an enzyme catalyzes the reaction and is strongly affected by: - Temperature - pH - Concentration of the enzyme and substrate

Question 28

Explain Optimum Temperature of Enzymes.

Answer 28

Enzymes are most active at an optimum temperature (37 degrees celsius). - They show little activity at low temperatures - They lose activity at high temperatures as denaturation occurs

Question 29

Explain Optimum pH of Enzymes.

Answer 29

Enzymes are most active at optimum pH, where proper tertiary structure of the protein is maintained. - They contain amino acid R groups with proper charges at optimum pH - They lose activity in low or high pH as tertary structure is disrupted

Question 30

An increases in Enzyme Concentration...

Answer 30

- Increases the rate of reaction - Binds more substrate with enzymes

Question 31

An increase in Substrate Concentration...

Answer 31

- Increases the rate of reaction - Eventually substrates an enzyme with substrates to give

Question 32

What is Vmax?

Answer 32

Maximum reaction velocity - at Vmax the enzyme is working as fast as it can. The enzyme is saturated with substrate.

Question 33

What is a Holoenzyme?

Answer 33

The combination of the cofactor with apoenzyme

Question 34

What are Inhibitors?

Answer 34

- are molecules that causes a loss of catalytic activity - prevent substrates from fitting into the active sites - can be classified as either reversible or irreversible

Question 35

Explain Reversible Inhibitors.

Answer 35

- Causes a loss of enzyme activity that can be restored. - Can act in different ways but do not form covalent bonds with the enzymes 2 Categories: - Competitive Inhibitors - Non Competitive Inhibitors

Question 36

Explain Competitive Inhibitors

Answer 36

Type of Reversible Inhibitor that competes for the active site. - has a chemical structure and polarity similar to the substrate.

Question 37

Non Competitive Inhibitors

Answer 37

Type of Reversible Inhibitor that acts on another site that is not the active site. - has a chemical structure and polarity different to the substrate.

Question 38

Explain Irreversible Inhibitors.

Answer 38

In a irreversible inhibition, enzyme activity is destroyed when: - the inhibitor covalently bond with R groups of an amino acid they may be near the active site. - the inhibitor changes the shape of the enzyme, which prevents the substrate from entering the active site.

Question 39

Explain Feedback Control.

Answer 39

A regulation process in which the formation of a product inhibit an earlier reaction.

Question 40

Explain Allosterism.

Answer 40

Allosterism is the binding for a regulator to a site (other than the active site) on the enzyme that modifies the enzyme's ability to bind the substrate to the active site. Two types: - Negative: inhibits enzyme action - Positive: stimulate enzyme action

Question 41

Explain Proenzymes.

Answer 41

- Zymogens or Proenzymes are produces in their inactive form and can be activated at a later time when they are needed.

Question 42

Explain Protein Modification.

Answer 42

The most common form of protein modification is addition or removal of a phosphate group. This group is located at the R groups of: - Serine - Threonine - Tyrosine