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6.2 Enzymes and Chemical Reactions pages 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.

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6 2 enzymes and chemical reactions pages 156 160


6 2 enzymes and chemical reactions pages 156 160

  • 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 energyC6H12O6 + 6O2

Products

Reactants


6 2 enzymes and chemical reactions pages 156 160


Enzymes in chemical reactions
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 additional substances are known as catalysts.

  • Enzymes are catalysts.


6 2 enzymes and chemical reactions pages 156 160

A catalyst lowers activation energy

  • Catalysts are substances that speed up chemical reactions

    • by decreasingactivation energy.

Enzymes are catalysts in

organisms.

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


6 2 enzymes and chemical reactions pages 156 160

Characteristics of Enzymes

  • Enzymes are proteins

  • 2. Enzymes are reusable!

  • 3. Enzymes denature in high temperatures

    • * denature = destroyed, broken apart, digested

    • * denaturation is not reversible

  • All enzymes end with ‘ase’.

  • Ex) Lactase breaks down Lactose (milk sugar)


6 2 enzymes and chemical reactions pages 156 160

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 releasedfrom the enzyme.

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

  • Enzymes are SPECIFIC (they only break down/put together one specific substance.)

    • *They will only FIT with certain substrates*

  • Substrates are brought together.

  • They attach to the active site of enzymes.

  • - Bonds are then made or broken.

  • - Product is released.



Induced fit model
Induced Fit Model between active site and substrate

  • Builds on the “Lock and Key” Model.

  • It adds that the enzyme active site physically changes to mold around and encompass the substrate(s).


6 2 enzymes and chemical reactions pages 156 160

An Enzyme at Work between active site and substrate

Reactant

Enzyme-Substrate

Complex

Products

Substrate

Active site

Unchanged

enzyme


How do enzymes speed up reactions
How do enzymes speed up reactions? between active site and substrate

  • Enzymes lower the activation energy of a reaction:


Factors that affect enzyme activity
Factors that Affect Enzyme Activity between active site and substrate

  • 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.


6 2 enzymes and chemical reactions pages 156 160

1. What is this graph showing? between active site and substrate

temperature and enzyme activity

2. What is the independent variable?

temperature

3. What is the optimum temperature for the enzyme?

40°C

4. At what temperature is the enzyme completely denatured?

62°C


Vocabulary
VOCABULARY between active site and substrate

  • 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


6 2 enzymes and chemical reactions pages 156 160