Bell Ringer

1
Bell Ringer

• Define the following terms in your own words.
  (Use a device if you need to!)
• Activation Energy
• Catalyst
• Enzyme

2
Catalysts and Enzymes

• Chapter 2 section 4

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Activation Energy

• Activation Energy the amount of energy needed
  to get a chemical reaction started.
• Most of the time, the activation energy must come
  from an outside source.
• Endothermic reactions require more activation
  energy than exothermic reactions.

4
Catalysts

• Catalyst ANY substance that speeds up a
  chemical reaction by lowering the activation
  energy
• Examples light, heat, stirring

5
Enzymes

• Many cells make catalysts called enzymes (a
  PROTEIN that acts as a catalyst).
• Cells then use enzymes to speed up chemical
  reactions that take place in cells by LOWERING
  the ACTIVATION ENERGY for the REACTION.
• Enzymes are like a coupon for the cost of the
  reaction.
• Enzymes are reusable.

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Fig. 2-20 Effect of Enzymes
Reaction pathway without enzyme
Activation energy without enzyme
Activation energy with enzyme
Reactants
Reaction pathway with enzyme
Products
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How Enzymes Work

• The reactants are called Substrates.
• The substrate has to bind to the enzyme in order
  to work.
• The enzyme and substrate are complimentary shapes
  meaning they have to fit together. (example
  lock key)
• Enzymes provide a place for the chemical reaction
  to occur.

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(Reactants)
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Effectiveness of Enzymes

• The effectiveness of enzymes can be changed by
  changes by
• Temperature (best at 370C or 98.60F)
• pH (best around a neutral pH)
• These change the effectiveness because HOT temp.
  extreme pH change the enzymes SHAPE.

10
Enzyme Substrate Animation

• http//highered.mcgraw-hill.com/sites/0072495855/s
  tudent_view0/chapter2/animation__how_enzymes_work.
  html