Enzymes

• Amino acids


  Recurring monomers that proteins are composed of
• Components of an amino acid

  • Central carbon
  • Amine group
  • Carboxyl group
  • Variable R-group
  • Hydrogen atom
• There are 20 different amino acids which are universal to all living organisms
• 1. group


  Gives the amino acid and the polypeptides they form their individual characteristics
• Types of amino acids

  • Essential
  • Non-essential
  • Conditionally essential
• Essential amino acids


  Cannot be produced by the body and must be obtained through the diet
• Non-essential amino acids


  Can be produced by the body (from other amino acids) and are therefore not required as part of the diet
• Conditionally essential amino acids

  Can be produced by the body, but can be limited or insufficient in some situations (such as pregnancy or illness)
• Polypeptides


  Chains of amino acids linked together by condensation reactions
• Peptide bonds


  Bonds connecting the monomers, formed between the amine group and carboxyl group of the amino acids involved
• Polypeptides can be anywhere from a handful of amino acids in length to tens of thousands, and individual amino acids can form a bond with any other amino acid
• The number of possible polypeptide sequences is close to infinite
• Genes


  Segments of DNA that code for the amino acid sequence for one specific polypeptide
• Proteins


  Polypeptides are the main component, may consist of just one polypeptide chain, or several polypeptide chains linked together, and may include other non-peptide molecules
• Levels of protein structure

  • Primary
  • Secondary
  • Tertiary
  • Quaternary
• Primary structure


  The specific sequence of amino acids in a peptide chain connected via peptide bonds
• Secondary structure


  Hydrogen bonding down the peptide backbone causes repetitive patterns to occur, the most common are alpha helices and beta sheets
• Tertiary structure


  Three-dimensional folding of the peptide chain due to interactions between the different side chains/R-groups
• Quaternary structure


  Some proteins are assemblies of several separate polypeptides, also known as protein subunits
• Protein denaturation


  Occurs when the chemical bonds holding a protein together are altered so it can no longer hold its three-dimensional shape, usually leading to a loss of function
• Causes of protein denaturation

  • Changes in temperature
  • Changes in pH outside the proteins optimum range
• Protein functions


  • Enzymes
  • Movement
  • Blood clotting
  • Transport
  • Hormones
  • Immunity
  • Membrane transport
• Fibrous proteins


  Insoluble structural components that are elongated with a dominant secondary structure
• Globular proteins


  Soluble functional tools that have a spherical shape and a dominant tertiary structure
• Insulin


  • Globular protein, hormone produced by the pancreas that regulates glucose uptake into the cells
• Immunoglobulin


  • Globular protein, also known as antibodies, they bind to bacteria or other pathogens marking them for other immune cells to destroy
• Collagen


  • Fibrous protein, rope like protein, gives strength to the skin, blood vessel walls, ligaments, tendons, teeth and bones
• Spider silk


  • Fibrous protein, a very strong protein that is extensible and resistant to breaking
• Actin and myosin


  • Contractile proteins that generate movement in muscle tissue by "sliding" across each other to shorten or lengthen the entire muscle
• Haemoglobin


  • A protein responsible for transporting oxygen in the blood of vertebrates comprised of four subunits, each containing an iron atom bound to a heme group
• Heme group


  Part of the haemoglobin protein structure
• Enzymes


  Most are globular proteins, biological catalysts that speed up the rate of chemical reactions within the cell, not changed or consumed by the reactions they catalyse
• Enzymes speed up the rate of chemical reactions
• Active site


  The region on the surface of the enzyme which binds to a substrate molecule
• Substrate


  Molecule that binds to the enzyme's active site
• The active site and the substrate complement each other in terms of both shape and chemical properties
• Once the reaction is complete the enzyme releases the products of the reaction
• Lactase


  • A digestive enzyme that breaks down the disaccharide lactose
• Glycolysis


  • The breakdown of glucose during cellular respiration uses numerous enzymes at different steps of the process