3.3 Enzymes and Activation Energy

Question 1

Enzymes help chemical
reactions take place

Answer 1

by lowering the Ea

(allow your body to use less
energy to drive reactions)

Question 2

DO NOT supply _____ for
reactions, but DO ___________

Answer 2

DO NOT supply energy for
reactions, but DO
influence energy changes
along the way

Question 3

Enzyme speed up the

Answer 3

rate of reaction

Question 4

The metabolism would be very slow without

Answer 4

Enzymes

Question 5

Enzymes act as….

Answer 5

catalysts

Question 6

Enzymes are almost always…

Answer 6

Proteins

(Some RNA molecules can act as enzymes)

Question 7

Maud Menten was the first to shed light on

Answer 7

role of enzymes and the rate of reactions

Question 8

Enzymes lower the _______ ______ of the transition state

Answer 8

Potential Energy

Therefore, more reactants reach the transition state faster, and products form more quickly

Question 9

The enzyme DOES NOT alter the

Answer 9

physical composition of the products

Question 10

The name of the enzyme is writetten

Answer 10

above the arrow

Ex. Maltase catalyzes the hydrolysis of maltose into 2 glucose molecules

Question 11

Activation Energy (Ea)

Answer 11

The amount of energy required to start a reaction

A certain amount of energy is needed to help break the bonds of chemicals

Question 12

Transition State

Answer 12

temporary state between reactants and products (before new bonds are formed)

Occurs when enough energy is required to begin reaction

Question 13

Even though a reaction may be spontaneous, the reaction will

Answer 13

will not take
place until the needed Ea is gained by the reactants

Question 14

What provides Ea?

Answer 14

• Thermal Energy
• Catalyst (Enzymes)

Question 15

Thermal Energy

Answer 15

causes more and more reactions to take place as more and more energy is released

Can destroy structural components of proteins at high temperature

Hard to regulate as increasing temperature would speed up ALL reactions in the cell,
not just one specific reaction

Question 16

Catalyst (Enzymes)

Answer 16

Allows reactions to occur using less energy

Can be regulated to control rates of reaction

Question 17

Lowering Ea with Enzymes

Answer 17

Because enzymes don’t alter reactants or products, the
change in FREE ENERGY (ΔG) of the reaction is unaffected

Question 18

How do Enzymes lower Ea

Answer 18

1. Brings Reactants Together
   * Orients molecules into a position so they can bind
2. Charged Enzymes Help Break Bonds
   * Charged functional groups help to attract reactants and
   break bonds
3. Enzyme Changes Shape of Substrate
   * The active site of the enzyme can strain/distort the substrate, which weakens its chemical bonds, thus reducing the energy required to break the bonds
   (Induced Fit Model)