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Chapter 5 Enzymes Lesson 2 - Characteristics of enzymes
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Chapter 5 Enzymes Lesson 2 - Characteristics of enzymes






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Chapter 5 Enzymes Lesson 2 - Characteristics of enzymes Chapter 5 Enzymes Lesson 2 - Characteristics of enzymes Presentation Transcript

  • Enzymes found at home
  • Biological washing powders
  • Enzyme power!
  • Qn : How would enzymes help to clean clothes with stains on them? Qn: Can any enzyme be used in biological washing powders?
  • * Characteristics of enzymes
  • Some characteristics of enzymes learnt earlier….
    • Enzymes
    • alter the rates of reaction
    • are specific
    • are required in minute amounts
  • Effect of temperature on enzyme action Note : For every increase in 10 °C in temperature, the rate of reaction doubles (until the optimum temp. is reached) (temp. at which enzyme is most active) denaturation
  • Why does enzyme activity increase as temperature increase?
    • All particles are in constant random motion
    • In a reaction, enzyme and substrate molecules move and collide with each other at random
    • Increasing temperature would increase the kinetic energy supplied to the reacting molecules
    • When the reacting molecules move faster, the substrate and enzyme molecules collide with each other more often
    • The rate of enzyme-substrate complex formation increases
    • However enzyme activity only increases till the optimum temperature
  • Why does enzyme activity decrease at higher temperature?
    • All enzymes are made of proteins
    • In most proteins the chains of amino acids are coiled or folded up to give the protein a 3D shape
    • The coils are held in place by weak H-bonds
    • An increase in temperature increases the vibrations in the atoms of the enzyme
    • At higher temperatures, the vibrations become so violent they break the bonds in the enzyme
    • The protein is said to be denatured
  • Denaturation
    • Results in the loss of the enzyme’s active site
    • Substrates are therefore unable to fit into the active site and no reaction will occur
    • pH changes (alkali or acid) also bring about denaturation
  • Effects of pH on enzyme action (optimum pH) (enzyme activity ↓ )
  • Points to note on pH:
    • Different enzymes work best in different optimum pH
    • Extreme changes in pH causes denaturation
    • Maximum activity at optimum pH (pH on either side causes activity to decrease)
  • Different enzymes = different optimum pH
  • Reaction rate vs substrate concentration curve What do you observe?
  • Limiting factor
    • Definition:
    • Any factor that directly affects the rate at which a process (e.g. chemical reaction) occurs if its quantity is changed
    • Note: If quantity of the factor is increased , the rate of the process increases
  • [substrate] ↑ ; rate of reaction ↑ till X Further ↑ ; no ↑ in rate [saturation of enzymes (limiting factor); amt. of products formed per unit time is the same] More enzyme more products formed per unit time till Y (enzyme conc. becomes the limiting factor)
  • Co-enzymes
    • Non-protein organic compounds
    • Some enzymes require it to bind to them before they can catalyse reactions
    • B complex vitamins are essential components of many co-enzymes
  • Applying study tip (mneumonics)
    • In pairs, list all the characteristics of enzymes and come up with a suitable mneumonics.
    • e.g. specific = S
    • alter reaction rate = A …..
    • Using first letter of the various characteristics to form a phrase…
  • Summary (Using Mnemonics)
    • Characteristics of enzymes
    • S
    • M
    • R
    • T
    • C
    • A
    • p
    • E
    pecific (lock and key hypothesis) inute amounts (renewable) eversible reactions emperature o-enzymes may be needed lter rates of chemical reactions (lowers activation energy) H nzyme & substrate concentrations
  • Overview Biological Molecules Water and Living Organisms Carbohydrates, Fats and Proteins Enzymes Lock & Key hypothesis Mode of Action Factors affecting enzyme reactions Speed up chemical Rxn Not chemically altered at the end Of Rxn Lowering Activation Energy Specificity Temperature pH
  • Quiz!
  • Quiz…
    • After observing some biological washing powders, it was noted that some brands recommend that clothes be washed at low temperatures (<45ºC). Why?
    Enzymes are affected by temperature. Regulating temperature ensures that the enzymes work within its temperature range to prevent denaturation.
  • Quiz
    • Why is it that some washing powders are able to endure higher temperatures?
    • Different enzymes used; different enzymes have different temperature range i.e. different optimum temperature as well!
    • What purpose are higher temperatures for?
    • To remove tougher stains, e.g. oil stains