Proteins and Enzymes

• Biological Macromolecules


  A large, organic molecule such as carbohydrates, lipids, nucleic acids and proteins.
• Amino Acids

  • Building blocks of proteins
  • Two distinct groups

  A) H

  B) H

  C) N

  D) C

  E) H

  F) R

  G) C

  H) O

  I) O

  J) H

  
• Joining of amino acids

  When two amino acids combine, the formation of a larger molecule occurs and the release of water (H₂O)

  
• Condensation


  Amino acids are joined together to form peptide or polypeptide chains, a water molecule is released.
• Hydrolysis


  Polypeptide chains are broken down into smaller peptide chains or simple amino acids. A water molecule provides a hydrogen and hydroxyl group.
• Protein structures

  • Primary
  • Secondary
  • Tertiary
  • Quaternary

  A) Primary

  B) Secondary

  C) Tertiary

  D) Quaternary

  
• Primary Structure of Proteins


  Joined by peptide bonds that make up one polypeptide chain.
• Secondary Structure of Proteins


  Alpha helix or beta-pleated sheets which are formed through hydrogen bonds between amino acid backbones.
• Tertiary Structure of Proteins


  Three-dimensional structure formed through many types of bonds and interactions consisting of groups of alpha helix and beta-pleated sheets.
• Quaternary Structure of Proteins


  The interaction of more than one polypeptide chain.
• Proteome


  Complete array of proteins produced by a single cell or organism in a particular environment.
• Globular Proteins

  • Easily soluble in water
  • Tertiary structure is critical to function
  • Polypeptide chains are folded into a spherical shape
  • They can exist as single chains or comprise several chains, as occurs in haemoglobin and insulin
• Fibrous Proteins

  • Form long shapes, and are only found in animals
  • Water insoluble
  • Very tough physically
  • Parallel polypeptide chains in long fibres or sheets
• Enzymes


  Proteins that act as biological catalysts, speeding up chemical reactions without being consumed.
• Reactant


  A substance that is changed during a chemical reaction
• Product


  The compound that is produced in a reaction
• Substrate


  A compound on which an enzyme acts
• Anabolic Reactions


  Smaller molecules are joined together to form larger ones, endergonic process meaning it requires energy and two substrate molecules bind to the active site.
• Catabolic Reactions


  Larger molecules are broken down, exergonic process meaning releasing energy, an example can include digestion.
• Exergonic & Endergonic Reactions

  • Both reactions are involved in metabolism and are catalysed by enzymes
  • An initial activation energy is required in order for these reactions to occur
• Activation Energy


  Minimum amount of energy required to initiate a chemical reaction. Products of reactions are formed by lowering the activation energy.
• Lock and Key Model

  A) Enzyme

  B) Substrate

  C) Enzyme-Substrate Complex

  D) Enzyme-Product Complex

  E) Products

  
• Induced Fit Model

  A) Enzyme-Substrate Complex

  B) Enzyme-Product Complex

  
• Enzyme Inhibitors


  A molecule that binds to an enzyme, reducing its activity by interfering with the enzyme in some way.
• Irreversible Inhibitor


  Bind covalently to one or more amino acids and alters the structure of the enzyme, affecting its active site permanently.
• Reversible inhibitors


  Used to control enzyme activity without the enzyme being permanently inhibited or damaged.