Enzymes

1
Chapter 2

• Chapter 2-4
• Enzymes

2
Chemical Reactions

• Process that changes one set of chemicals into
  another set of chemicals
• Chemical reactions occur at different rates

3
Chemical Reactions

• Reactants- the elements or compounds that enter
  the reaction
• Products- the elements or compounds that are
  produced by a chemical reaction

4
Chemical Reactions

• Chemical reactions always involve the breaking of
  bonds in reactants and the formation of new bonds
  in products

5
Energy in Reactions

• Energy is released or absorbed whenever chemical
  bonds are broken
• Many chemical reactions will not occur without a
  source of energy

6
Activation Energy

• Activation energy- the energy needed to get a
  reaction started

7
Activation Energy

• Example Using a match to start a fire
• Figure 2-19 on page 50

8
Catalysts

• Some reactions have activation energies that are
  very high!!!
• The activation energy is so high that its hard
  for the reaction to occur
• So, nature uses a catalyst to start the reaction

9
Catalyst

• A catalyst is a substance that speeds up the rate
  of a chemical reaction
• It does this by lowering the activation energy
• Figure 2-20 on page 51

10
Catalyst
11
Enzymes

• Enzymes- proteins that act as catalysts
• Enzymes speed up chemical processes that occur in
  cells!!

12
Enzyme Action

• Remember, the point of an enzyme is to help
  overcome the reactions high activation energy!
• Enzymes are used to trap tame energy

13
Enzyme-Substrate Complex

• Enzymes contain a special active site
• The active site is waiting to combine with
  reactants
• The reactants that enter an enzymes active site
  are called substrates

14
Enzyme-Substrate Complex
15
Enzyme Reaction
16
Enzyme Reaction

• Step 1 Enzyme waits for substrate(s) to enter
  active site
• Step 2 Substrates enter active site
• Step 3 Activation energy is lowered in the
  presence of the enzyme
• Step 4 Reaction occurs, substrates change
  chemical composition (products formed)
• Step 5 Products leave enzyme

17
Enzyme Reactions

• Figure 2-21 on page 52
• Another example

18
Enzyme Regulation

• Certain factors affect the productivity of
  enzymes
• Temperature
• pH
• Competitive inhibitors

19
Competitive Inhibitor

• Competitive inhibitors block the active site of
  an enzyme and inhibit the substrate