Enzymes

Question 1

Enzyme

Answer 1

A macromolecule that acts as a catalyst: A chemical agent that speeds up a reaction without being consumed by the reaction

–> Organic biological catalyst
–> Ends in -ase

Question 2

Substrate

Answer 2

The molecule (reactant) on which the enzyme acts upon

Question 3

Bond Breaking vs Forming

Answer 3

Bond Breaking = Input Energy

Bond Forming = Release Energy

Question 4

Endergonic

Answer 4

Absorbs more energy than is released

Question 5

Exergonic

Answer 5

Releases more energy than is absorbed

Question 6

Activation Energy

Answer 6

(Ea) Energy required to initially break bonds (start the reaction) –> Get over the hump

Question 7

Delta G

Answer 7

Net free energy released

Energy of Products - Energy of Reactants

Question 8

Enzymes and Activation Energy

Answer 8

Enzymes lower activation energy for reactions, they DO NOT lower Delta G

Question 9

Catalytic Cycle of an Enzyme

Answer 9

1) Enzyme and substrate are available

2) Substrate binds to enzyme –> (Forms “enzyme-substrate” complex)

3) Substrate is converted to products and products are released

Question 10

Active Site

Answer 10

The specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis takes place

Question 11

Properties of Enzymes (4)

Answer 11

1) Enzymes lower activation energy

2) Enzymes are usually proteins

3) Enzymes are usually named by adding (-ase) to the end of substrate name

4) Enzymes are substrate specific

–> However, not lock and key model, follows induced fit model

Question 12

How Enzymes Work: 3 possibilities

Answer 12

1) In reactions with 2 or more reactants: Active site provides template on which substrates can come together with proper orientation to react

2) Stretch and Strain Bonds: Active site clutches bound substrate and stretches them towards their transition state form (Lowers Ea)

3) Create Favorable Microenvironment (Ex: providing more acidic environment)

Question 13

Vmax

Answer 13

Maximum reaction rate –> All enzymes “full and working”

Question 14

Enzyme Saturation

Answer 14

All enzymes at full capacity:

Only way to increase reaction rate in this case is to increase number of enzymes

Question 15

Km

Answer 15

Concentration of substrate at which enzyme works at 1/2 the max rate

–> Indicates how tightly the substrate is bound to the enzyme

1) Greater Km = Lower Binding Affinity

2) Lower Km = Higher Binding Affinity

Question 16

Effects of Environmental Conditions

Answer 16

Changes to temp, pH, or salinity can alter enzymatic function

Question 17

Cofactors

Answer 17

INORGANIC –> Usually divalent cations (minerals—EX: Mg2+, Ca2+, Mn2+)

Any non-protein molecule or ion that is required for the proper functioning of an enzyme

Question 18

Coenzymes

Answer 18

ORGANIC –> Mostly vitamins

Supply reactive atoms that are necessary for the reaction but are not available at the active site

Question 19

Competitive Inhibitor

Answer 19

A molecule that directly competes with the substrate for the active site

BINDS TO THE CATALYTIC SITE

–> A physical block: Can be removed by adding more SUBSTRATE

Question 20

Non-Competitive Inhibitor

Answer 20

A molecule that binds outside the active site (NO PHYSICAL competition)

–> Inhibits by causing changes to the conformation of the active site (so that the substrate can’t bind)

Question 21

Allosteric Regulation

Answer 21

A reversible, non-competitive inhibitor (like a light switch)

–>Must have 2 sites: Active and allosteric

Question 22

Allosteric Regulators

Answer 22

Regulators bind to the allosteric site to change activity of enzyme

1) Activator = Stabilizes the active conformation of the active site

2) Inhibitor = Stabilizes the INactive conformation of the active site

Question 23

Cooperativity

Answer 23

A form of allosteric activation

–> The binding of one substrate molecule facilitates the binding of other substrate molecules

(Has multiple active sites)

Question 24

Feedback Regulation

Answer 24

The final product of a chain of enzymatic reactions allosterically inhibits the first enzyme of the chain

–> Essentially turns itself (the chain reaction) off

–> Prevents the uncontrollable accumulation of products