Enzymes: Helper Protein molecules

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Enzymes Helper Protein molecules
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Chemical reactions of life

• Processes of life
• building molecules - ANABOLIC
• Synthesis
• breaking down molecules - CATABOLIC
• digestion

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Nothing works without enzymes!

• How important are enzymes?
• all chemical reactions in living organisms
  require enzymes to work
• building molecules
• synthesis enzymes
• breaking down molecules
• digestive enzymes
• enzymes speed up reactions

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Enzymes are proteins

• enzymes are named for the reaction they help
• sucrase breaks down sucrose
• proteases breakdown proteins
• lipases breakdown lipids
• DNA polymerase builds DNA

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Enzymes arent used up

• Enzymes are not changed by the reaction
• used only temporarily
• re-used again for the same reaction with other
  molecules
• very little enzyme needed to help in many
  reactions

substrate
product
enzyme
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Its shape that matters!

• Lock Key model
• shape of protein allows enzyme substrate to fit
• specific enzyme for each specific reaction

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What affects enzyme action

• Correct protein structure
• correct order of amino acids
• why? enzyme has to be right shape
• Temperature
• why? enzyme has to be right shape
• pH (acids bases)
• why? enzyme has to be right shape

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More about Enzymes What Affects Enzymes
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Enzyme vocabulary

• Enzyme
• helper molecule
• Substrate
• molecule that enzymes work on
• Enzyme-substrate complex
• enzyme molecule temporarily joined
• Active site
• part of enzyme that substrate molecule fits into

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Examples of Classification of Enzymes

• Oxidoreductoases
• oxidases - oxidize ,reductases reduce
• Transferases
• transaminases transfer amino groups
• kinases transfer phosphate groups
• Hydrolases
• proteases - hydrolyze peptide bonds
• lipases hydrolyze lipid ester bonds
• Lyases
• carboxylases add CO2
• hydrolases add H2O

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• Apoenzyme the protein part of an enzyme.
• Cofactor a nonprotein portion of an enzyme that
  is necessary for catalytic function examples are
  metallic ions such as Zn2 and Mg2.
• Coenzyme a nonprotein organic molecule,
  frequently a B vitamin.

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• Enzyme activity a measure of how much a reaction
  rate is increased.
• The rate of an enzyme-catalyzed reaction is
  effected by
• Enzyme concentration
• Substrate concentration
• Temperature
• pH

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• The effect of enzyme concentration on the rate of
  an enzyme-catalyzed reaction. Substrate
  concentration, temperature, and pH are constant.

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Substrate concentration

• Effect on rates of enzyme activity
• as increase amount of substrate increases how
  fast the reaction happens
• more substrate more frequently they collide
  with enzyme

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• The effect of substrate concentration on the rate
  of an enzyme-catalyzed reaction. Enzyme
  concentration, temperature, and pH are constant.

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Temperature

• Effect on rates of enzyme activity
• Optimum temperature
• greatest number of collisions between enzyme
  substrate
• human enzymes 35- 40C (body temp 37C)
• Raise temperature
• denature protein unfold lose shape
• Lower temperature T
• molecules move slower
• decrease collisions

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• The effect of temperature on the rate of an
  enzyme-catalyzed reaction. Substrate and enzyme
  concentrations and pH are constant.

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pH

• Effect on rates of enzyme activity
• pH changes protein shape
• most human enzymes pH 6-8
• depends on where in body
• pepsin (stomach) pH 3
• trypsin (small intestines) pH 8

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• The effect of pH on the rate of an
  enzyme-catalyzed reaction. Substrate and enzyme
  concentrations and temperature are constant.

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pH
stomachpepsin
intestinestrypsin
reaction rate
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pH
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• Inhibition any process that makes an active
  enzyme less active or inactive.
• Competitive inhibitor any substance that binds
  to the active site of an enzyme thereby
  preventing binding of substrate.
• Noncompetitive inhibitor any substance that
  binds to a portion of the enzyme other than the
  active site and thereby inhibits the activity of
  the enzyme.

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• Enzyme kinetics in the presence and absence of
  inhibitors.

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• Allosterism enzyme regulation based on an event
  occurring at a place other than the active site
  but that creates a change in the active site.
• An enzyme regulated by this mechanism is called
  an allosteric enzyme.
• Negative modulation inhibition of an allosteric
  enzyme.
• Positive modulation stimulation of an allosteric
  enzyme.

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The Allosteric Effect

• The allosteric effect. Binding of the regulator
  to a site other than the active site changes the
  shape of the active site.

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