Proteins

• Amino acids


  Molecules that proteins are made out of
• Amino acid structure


  • Central set of three atoms: nitrogen, origin carbon, another carbon (NCC)
  • Amine group (NH2) branching from nitrogen
  • Carboxyl group (COOH) branching from central carbon
  • Variable R group branching from central carbon
• There are 20 different amino acids
• Condensation reaction


  Reaction that links two amino acids together, releasing a water molecule
• Protein structure levels


  • Primary: Amino acid sequence
  • Secondary: Alpha helices, beta pleated sheets
  • Tertiary: Interactions between side chains
  • Quaternary: Multiple polypeptide chains
• Quaternary protein


  • Hemoglobin
• Denaturation


  When a protein's structure is altered to the point it can no longer function
• Causes of denaturation


  Changes in temperature, pH
• Protein synthesis


  DNA -> mRNA -> Ribosome -> Amino acids -> Folding -> Functional protein
• Spider silk is stronger than steel by weight
• Amino acids

  The building blocks of proteins
• Amino acids

  • Containing a carboxyl, an ammine and an R group
  • Monomers of proteins
  • Linked together by peptide bonds to form complex proteins
• Proteins are important organic molecules that carry out major functions in cells and in the extracellular space
• Although there are only 20 different amino acids, millions of proteins exist as these monomers can be linked in any given sequence
• The specific sequence of each protein is coded for in the genetic material of the organism
• Central Dogma of molecular biology

  1. DNA is transcribed into RNA

  2. RNA is translated into proteins
• Protein primary structure

  • Consists of a string of amino acids (the amino acid sequence)
• Protein secondary structure


  • Formation of alpha helices and beta pleated sheets
  • Stabilized by the formation of hydrogen bonds
• Protein tertiary structure

  • Formation of the 3D structure of the polypeptide
  • Due to interactions between the R groups of the amino acids
  • Includes disulphide bridges, hydrogen bonds, van der waal interactions, and ionic bonds
• Protein quaternary structure

  • Multiple polypeptide chains combined to form a single protein
• Formation of a dipeptide

  1. Condensation reaction between carboxyl group of one amino acid and amino group of another

  2. Release of water molecule
• Breakdown of a dipeptide

  1. Hydrolysis reaction

  2. Water is added to break the peptide bond
• Protein functions

  • Structural (e.g. collagen)
  • Transport (e.g. hemoglobin)
  • Movement (e.g. actin)
  • Defence (e.g. immunoglobulins)