Enzymes

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Enzymes

• A protein catalyst
• Enzymes are important proteins found in living
  things. An enzyme is a protein that changes the
  rate of a chemical reaction.
• They speed metabolic reactions.

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Enzymes
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A specific enzyme catalyzes each cellular reaction

• Enzymes are selective
• This selectivity determines which chemical
  reactions occur in a cell

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How an enzyme works
Enzyme(sucrase
Substrate(sucrose)
Activesite

• The enzyme is unchanged
• and can repeat
• the process

Glucose
Fructose
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Enzyme available with empty active site
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Products are released
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Substrate is converted to products
Substrate binds to enzyme with induced fit
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Enzyme video clipdouble click
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The cellular environment affects enzyme activity

• Enzyme activity is influenced by
• temperature Denaturationprocess
• salt concentration in which protein
  unravels
• pH losing its
  shape hence function

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Enzyme activity

• Some enzymes require nonprotein cofactors
  (usually minerals)
• Some cofactors are organic molecules called
  coenzymes ( usually vitamins)

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Enzyme inhibitors block enzyme action

• Inhibitors interfere with enzymes
• A competitive inhibitor takes the place of a
  substrate in the active site
• A noncompetitive inhibitor alters an enzymes
  function by changing its shape

Substrate
Active site
Enzyme
NORMAL BINDING OF SUBSTRATE
Competitiveinhibitor
Noncompetitiveinhibitor
ENZYME INHIBITION
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Connection Some pesticides and antibiotics
inhibit enzymes

• Certain pesticides are toxic to insects because
  they inhibit key enzymes in the nervous system
• Many antibiotics inhibit enzymes that are
  essential to the survival of disease-causing
  bacteria
• Penicillin inhibits an enzyme that bacteria use
  in making cell walls