6.2 Enzymes and Chemical

Reactionspages 156-160

• Chemical reactions take place all the time.• Chemical reactions change substances

into different ones by breaking and forming chemical bonds.

• Reactants are the starting materials.• The newly formed substances are called

products, which are different from the reactants.

• Reactants on the left, Products on right.For example:

6CO2 +6H2O+light energyC6H12O6 + 6O2

Reactants

Products

• The key to starting a chemical reaction is energy.

• Activation energy is the minimum amount of energy needed for reactants to form products in a chemical reaction.

Enzymes in Chemical Reactions

• Sometimes, the energy required for a reaction to take place is too high.

• The reaction can’t take place unless additional substances are present to reduce the activation energy.

• These substance are known as enzymes, which serve as catalysts.

Catalysts are substances that speed up chemical reactions by decreasing activation energy.

A catalyst lowers activation energy

Enzymes are catalysts

Most reactions would occur too slowly without the help of enzymes, which speed up chemical reactions.

Characteristics of Enzymes

1. Enzymes are proteins

2. Enzymes are reusable!

3. Enzymes denature in high temperatures* denature = destroyed, broken apart, digested* denaturation is not reversible

4. All enzymes end with ‘ase’. Ex) Lactase breaks down Lactose (milk sugar)

Substrates bind to anenzyme at certain places

called active sites.

The enzyme bringssubstrates together and

weakens their bonds.

The catalyzed reaction formsa product that is released

from the enzyme.

- Substrates are brought together.- They attach to the active site of enzymes.- Bonds are then made or broken.- Product is released.

The lock-and-key model helps illustrate how enzymes function.

• Enzymes are SPECIFIC (they break down only one thing) *They will only FIT with certain substrates*

‘Lock and Key Model’ – says there is a perfect fit between

active site and substrate

VOCABULARY

• Enzymes – biological catalysts or special proteins that speed up chemical reactions

• Catalysts – substances that speed up chemical reactions)

• Substrates – materials that bind to the enzyme

• Active Site - Location on the enzyme where the substrate binds

An Enzyme at WorkReactant

ProductsEnzyme-SubstrateComplex

Active site

Unchanged enzyme

Substrate

How an enzyme affects a chemical reation:

How do enzymes speed up reactions?

• Enzymes lower the activation energy of a reaction:

Factors that Affect Enzyme Activity

1. TEMPERATURE- Too warm, enzyme will denature.- Too cold, enzymatic activity will slow down.

2. pH

- a change in pH can change the shape of the enzyme so that substrates can’t fit into active site.

3. What is the optimum temperature for the enzyme?

4. At what temperature is the enzyme completely denatured?

1. What is this graph showing?

2. What is the independent variable?

62°C

40°C

temperature and enzyme activity

temperature

• If you did not complete lab. Do that FIRST!• Enzyme worksheet• Pg 160 1 and 4• Pg 175-176: 1,2,4,7,14-23