Exam 2 review

• amino acids are used to make nitrogenous bases, such as purines and pyrimidines
• some hormones that require amino acids include thyroxine, epinephrine, and histamines
• proteins

  structure - joined together via head to tail linkages (C terminus of one aa to N terminus of other amino acid) to create peptide bonds
• the primary structure of an amino acid is the sequence of amino acids
• the secondary structure of a protein is the shape of the chain; it is maintained by hydrogen bonds between amino acids
• secondary structures include alpha helices and beta pleated sheets

  3d shape
• tertiary shape of a protein is the way individual secondary structures are arranged

  • interaction of R groups determines tertiary structure
• the tertiary shape of a protein is responsible for many physical/chemical properties of proteins
• quaternary shapes of proteins is the arrangement of tertiary structures in space

  e.g. the alpha globins or beta globins coming together to make a larger structure represents the protein's quaternary shape
• only the largest proteins have quaternary shape
• the charge of an amino acid depends on the pH of the surrounds
• in an alkaline solution, amino acid will act as an acid and donate proton form its C terminus
• at a pH of 8.6, our bodies proteins will donate a proton and become negative
• in an acidic solution, amino acid will act as a base and accept a proton donated at the N terminus
• The aa donating a proton causes it to become negative
• the aa accepting an H at the N terminus causes it to have a positive charge
• the pH of blood is between 7.35 and 7.45
• in many cases, serum proteins have a net neutral charge where the protein will neither accept or donate a proton, this is called the protein's isoelectric point
• every protein has a pH in which is has no net charge, meaning there is no extra proton at the N terminus and no loss of H at the C terminus
• a Zwitter ion occurs when the the C terminus's OH group donates a proton to the N terminus, causing OH to become negative and N to become positive
• solubility of proteins

  • proteins will enclose water in their crystal if in an aqueous solution
  • if reconstituting lyophilized material, must rock for 30 minutes so proteins are fully reconstituted
• solubility of proteins

  • in salt concentration solutions, proteins can precipitate out
  • this was one of the earlier ways protein concentration was determined
• Antigenicity of proteins - when injected into other species, human proteins cause formations of antibodies

  • we can use those antibodies to develop assays
  • murine - mouse
  • bovine - cow
• protein functions

  • enzymes
  • 1500 known enzymes
• enzymes are biological catalysts which lower activation energy

  they are not consumed or changed in reaction, can be reused
• protein function

  • structural
  • e.g. collagen
• protein function

  • contractile - provides mechanism for contraction/relaxation of muscle
  • thin and thick sarcomeres are made of proteins
• protein function

  • antibodies/antigens
  • both are made up of protein
  • antigen may have things attached (often glycoproteins)
• protein function

  • transport -
  • provides gateways to allow things in and out of cell
  • e.g. symporter proteins - when certain requirement fulfilled, opens one side and closes the other)
  • e.g. when 3 Na ions present on one side, allows passage of Na ions by flipping
• protein function

  • transport -
  • carries material through body (e.g. albumin transports food to be absorbed)
  • carries materials in and out of cells
  • e.g. ferritin (transports and stores iron safely) and transferrin (transports iron)
• protein function

  • osmotic pressure - force causing reabsorption of water due to higher concentration of particles; albumin is the main determinant of osmotic pressure
• protein function

  • hormones/receptors - some hormones are made of proteins; others are made of cholesterol (aka steroids)
  • hormones of protein go around bloodstream looking for compatible receptors
  • hormones are also called ligands
  • receptors are many times made of proteins for ligands
• albumin

  1. Major functions
  2. Accounts for up to 80% of the osmotic pressure in plasma
  3. Transport - binds and carries numerous substances in plasma
• a-1 globulins include a-1 antitrypsin, a-1 fetoprotein, a-1 acid glycoprotein, a-1 lipoprotein, a-1 antichymotrypsin, inter-a-trypsin inhibitor, and Gc-globulin
• albumin constitutes 53-65% of serum proteins
• a-1 globulins constitute 2.5-5.0% of serum proteins
• a-2 globulins constitute 7-13% of serum proteins
• b-globulins constitute 8-14% of serum proteins
• y-globulins constitute 12-22% of serum proteins
• • Imunogen - molecule that induces immune response