Enzymes

    Cards (23)

    • What are enzymes?
      Biological catalysts that increase the rate of a chemical reaction without being permanently altered themselves
    • What is an advantage of enzymes in the body?
      They enable cellular reactions to take place at lower temperatures
    • What is the active site of an enzyme?
      The region of an enzyme to which a substrate molecule binds and the reaction takes place
    • Why are enzymes described as having a ‘high specificity’ for their substrate?
      Only substrates with a specific, complimentary shape can fit into an enzymes active site
    • Describe the ’lock and key’ model
      1. Substrate collides with the active site of an enzyme
      2. Substrate binds, enzyme-substrate complex forms
      3. Substrate converted to products
      4. Products released from the active site which is now free to bind to another substrate
    • What factors affect the rate of an enzyme controlled reaction?
      Temperature
      pH
      • Substrate concentration
    • Explain how increasing temperature initially affects the rate of an enzyme-controlled reaction
      • As temperature increases, molecules have more kinetic energy
      Movement of molecules increases
      • Probability of a successful collision increases
      • More enzyme-substrate complexes form
      • Rate of reaction increases
    • Explain how increasing temperatures above the optimum affects the rate of an enzyme-controlled reaction
      • Temperature increases above the optimum
      • Increases vibrations break bonds in enzyme’s structure
      • Active site changes shape, enzyme is denatured
      • No more enzyme-substrate complexes can form
      • Rate of reaction decreases
    • Explain how pH affects the rate of an enzyme-controlled reaction
      • Enzymes have an optimum pH
      • pH shifts from the optimum
      • Bonds in the enzyme’s structure are altered
      • Active site changes shape, enzyme is denatured
      • Rare of reaction decreases
    • Explain how the substrate- concentration affects the rate of an enzyme-controlled reaction
      • Substrate concentration increases
      • Number of substrate molecules in the same volume increases
      • Probability of a successful collision increases
      • More enzyme-substrate complexes form
      • Rate of reaction increases
      • Once all active sites become full, the rate of reaction plateaus
    • How can the rate of an enzyme-controlled reaction be calculated when given a value for time?
      Rate = 1/time
    • What are the units for rate?
      S1^-1
    • Why must large organic molecules be broken down into smaller, simpler units in the body?
      Large molecules are too big to be absorbed across the surface of the gut wall
      • Large molecules are broken down into smaller molecules for absorption into the bloodstream
    • Give an example of the breakdown of large molecules into smaller molecules in plants
      Starch is broken down by enzymes into simpler sugars which are respired to release energy
    • What type of molecule are proteins and carbohydrates?
      Polymers
    • What are the monomers of carbohydrates?
      Simple sugars
    • Which group of enzymes catalyses the breakdown of carbohydrates?
      Carbohydrases
    • Which type of carbohydrase catalyses the breakdown of starch?
      Amylase
    • What are the monomers of proteins?
      Amino acids
    • Which type of enzyme catalyses the breakdown of proteins?
      Protease
    • Function of lipases
      Enzymes which catalyse the breakdown of lipids into fatty acids and glycerol
    • Why are small molecules synthesised into larger organic molecules in the body?
      • Large molecules are used for storage (e.g. glycogen)
      • Large molecules are used to build structures (e.g. organelles)
    • Which enzyme catalyses the formation of glycogen from glucose?
      Glycogen synthase
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