General properties of enzymes

• what is an enzyme?

  a biological catalyst; a protein made by cells that alters the rate of a chemical reaction without being used up by the reaction
• what kind of proteins are enzymes?

  globular proteins
• why are enzymes called ‘biological’ catalysts?

  as they are made by living cells
• what properties do enzymes and chemical catalysts share in the reactions they catalyse?

  • they speed up reactions
  • they aren’t used up
  • they aren’t changed
  • they have a high turn over number (i.e. they catalyse many reactions per second)
• what type of reactions do enzymes catalyse?

  they only catalyse reactions that are energetically favourable and that would happen anyway
• what would happen to reactions in cells without enzymes?

  reactions in cells would be too slow to be compatible with life
• what is a catalyst?

  an atom or molecule that alters the rate of a chemical reaction without taking part in the reaction of being changed by it
• what is the basic structure of an enzyme?

  they are proteins with tertiary structure and the protein chain folds into a spherical or globular shape with hydrophilic R groups on the outside of the molecules, making enzymes soluble
• how is each enzyme different?

  each enzyme has a particular sequence of amino acids
• what do the elements in the R group determine?

  they determine the bonds the amino acids make with each other
• what are the bonds that the amino acids make with each other?

  • hydrogen bonds
  • disulphide bonds
  • ionic bonds
• what do the bonds that the amino acids make with each other do?

  they hold the enzyme molecule in its tertiary form
• what is an active site?

  the specific three-dimensional (3D) site on an enzyme molecule to which the substrate binds by weak chemical bonds
• what is the strength of a chemical bond?


  they vary in strength, depending on the atoms that they join and on their chemical environment
• whats the strength of hydrogen bonds?

  they are weak but if there are many of them, they have a significant binding effect (they become stronger)
• what type of bond is a disulphide bond?

  covalent bond
• what is this a diagram of?

  an anabolic reaction

  
• what is this a diagram of?

  a catabolic reaction