Enzymes

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Enzymes

• Biochemistry

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What You Need to Know!

• Enzymes work by lowering the energy of
  activation.
• The catalytic cycle of an enzyme that results in
  the production of a final product.
• The factors that influence the efficiency of
  enzymes.

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Special Proteins Enzyme

• Enzymes are proteins that speed up the rate of a
  chemical Rx
• Making/breaking covalent bonds in cells
• Also called a biological catalyst
• Suffix -ase
• Enzyme
• Substrate(s) ? product(s)

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• Enzymes are large 3-D proteins that have a groove
  where they bind the substrate(s) ? active site

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Enzyme

• Each enzyme
• Has a specific 3-D structure (due to the number
  and order of AA)
• Can interact only with one type of substrate that
  fits in the active site Lock and Key model

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Catalytic Cycle

1. Enzyme finds substrate
2. Substrate binds to active site enzyme-substrate
   complex

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Enzyme Rx

• Enzyme transforms the substrate into product
  enzyme product complex
• Enzyme releases product
• An enzyme can carry out a chemical Rx over and
  over again
• it is not used up in the Rx
• Substrates are used up

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Activation Energy

• Transformation from reactants to products
  requires the input of energy activation energy
• Enzymes can speed up a Rx because they lower the
  activation energy of the Rx

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Enzyme Rx RatesDepend On

• Substrate concentrations
• The more substrate, the faster the rate
• Until present enzymes reach capacity
• Enzyme concentrations
• The more enzymes the faster the rate
• Until substrate concentration becomes limiting
  factor
• pH
• Can slow the rate due to denaturation of enzyme

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Enzyme Rx RatesDepend On

• Temperature
• Can slow rate due to denaturation of enzyme
• Presence of inhibitors
• Can slow down or block enzymes

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To be continued
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Factors that affect enzyme activity

• pH
• Enzyme pepsin in stomach does not become active
  until it is in an acidic pH
• Temperature
• Each enzyme has an optimal temperature range
• Cofactors or coenzymes
• Bind to the enzyme to make it functional
• Ex metals such as Zn, Fe, Co, and vitamins
• Inhibitors

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1. Competitive Inhibitor (reversible)

• Mimics substrate molecule(s) (flat toothpicks)
  but cannot be metabolized
• slows down Rx rate

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2. Non-competitive/allosteric inhibitors
(reversible)

• Molecules that do not bind to active site but at
  the allosteric (other) site
• leading to conformation (change in shape)
• Can turn off active site

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Enzymes

• http//www.youtube.com/watch?vPILzvT3spCQfeature
  related

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3. Non-competitive inhibitors-(irreversible)

• Toxins
• Poisons

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Enzyme Regulation

• Chemical chaos would result if all metabolic
  pathways in the body work simultaneously
• Regulation through
• Transcription/translation
• Active regulation of enzymes already made
• Allosteric Regulation
• Feedback Inhibition

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Active Regulation

• Allosteric Regulation
• Reversible non-competitive inhibitors or
  activators that the body makes
• binds to allosteric site
• Feedback Inhibition
• In long metaboloic pathways final products
  becomes allosteric inhibitors to the first enzyme