BIOCHEM

• Amino acids Building blocks of proteins, contain both an amine and an acid, 20 common in nature, all 19 except glycine are stereoisomers
• Classes of amino acids based on polarity of side chains

  • Nonpolar
  • Polar, neutral
  • Polar acidic
  • Polar basic
• Polar, uncharged amino acids Have R groups with OH, amide, sulfhydryl/thiol groups, can H-bond with water, found on surface of globular proteins, soluble in aqueous solution
• Non-polar/hydrophobic amino acids Have aliphatic or aromatic R groups, found in the interior of globular proteins, insoluble core
• Electrically charged amino acids


  • Negatively charged (Aspartic acid, Glutamic acid)
  • Positively charged (Lysine, Arginine, Histidine)
• Essential amino acids Amino acids that must be supplied in the diet for proper growth and development
• Peptide bondFormed by dehydration synthesis, allows free rotation of attached atoms, produces various shapes of polypeptide 

• Polypeptide chain


  Unbranched chain of amino acids
• Protein


  May consist of one or more polypeptide chains
• Simple peptides

  • Oxytocin
  • Vasopressin
• α-helix


  • Most common type of secondary structure, coiled and helical, each amide H and carbonyl O involved in H bonds, carbonyl O links to amide H 4 amino acids away, H bonds parallel to long axis, right-handed helix, repeat distance 5.4 angstroms, 3.6 amino acids per turn
• β-pleated sheet

  • Second most common secondary structure, appears similar to folds of fabric, all carbonyl O and amide H involved in H bonds, chain nearly completely extended, can be parallel or antiparallel
• Types of interactions maintaining tertiary structure

  • Disulfide bridges
  • Salt bridges
  • Hydrogen bonds
  • Hydrophobic interactions
• The three-dimensional structure of proteins is determined by the primary, secondary, tertiary, and quaternary structures.
• Transport proteins carry materials from one place to another in the body.
• The proteins hemoglobin and myoglobin are responsible for transport and storage of oxygen in higher organisms, respectively.
• Derived from the Greek word proteios meaning “first” to indicate the central roles that proteins play in living organisms
• Myosin and actin contract muscle fiber
• Hemoglobin transports oxygen. Lipoproteins transport lipids
• Casein stores protein in milk. Ferritin stores iron in the spleen and liver.
• Insulin regulates blood glucose level.
• Growth hormone regulates body growth
• Sucrase catalyzes the hydrolysis of sucrose. Trypsin catalyzes the hydrolysis of proteins
• Immunoglobulin stimulates immune response
• Stereoisomers are compounds that have the same constitution but differ in the spatial arrangement of their atoms.
• The α-carbon of amino acids is chiral
• Glycine is the only common amino acid that is not chiral.
• Serine and Threonine Bears hydroxylic R group.
• Asparagine and Glutamine has amide-bearing side chain
• Tyrosine Has a phenolic group, which, together with aromatic groups of F and W, accounts for most of the UV absorbance and fluorescence exhibited by proteins.
• Cysteine forms a disulfide bond to another cysteine residue through the oxidation of their thiol groups.
• Leucine and Isoleucine Has isomeric butyl groups
• Glycine Has the smallest possible side chain, an H atom
• Alanine Has methyl group -CH3
• Valine Has aliphatic hydrocarbon side chain
• Methionine Has a thiol ether side chain that resembles an n-butyl group in many of its physical properties (C and S have nearly equal electronegativities and S is about the size of a methylene group)
• Proline A cyclic secondary amino acid has conformational constraints imposed by the cyclic nature of its pyrrolidine side chain, which is unique among the "standard" 20 amino acids.
• Phenylalanine Has phenyl moiety
• Tryptophan With indole group, contain aromatic side chains, which are are characterized by bulk as well as nonpolarity.
• Negatively charged above pH 3; often referred to as Aspartate in its ionized state.

  Negatively charged above pH 3; often referred to as Glutamate in its ionized state.