AMINO ACIDS

• Amino Acids


  The basic building blocks of proteins

  
• Proteins


  • Made up of chains of amino acids
  • Found in every cell in an organism
  • Involved in most of the body's functions and processes
  • The sequence of amino acids is determined by the DNA

  
• Oligopeptides


  Few amino acid residues
• Polypeptides


  More than 20 amino acids
• Protein


  • Can be made up of one polypeptide chain or more
  • Typically 100 to 10,000 amino acids linked together

  
• Structure of Amino Acids


  • Contains an amino group, a carboxyl group, a hydrogen atom, and a side chain (R group)

  
• Peptide bond


  The chemical bond formed between the carboxyl group of one amino acid and the amino group of another, linking them together

  
• Primary structure of proteins


  The sequence of amino acids in a polypeptide chain

  
• The sequence of a protein is determined by the DNA of the gene that encodes the protein

  
• A change in the gene's DNA sequence may lead to a change in the amino acid sequence of the protein
• Even changing just one amino acid in a protein's sequence can affect the protein's overall structure and function
• A single amino acid change is associated with sickle cell anemia, an inherited disease that affects red blood cells

  
• Secondary structure of proteins


  Local folded structures that form within a polypeptide due to interactions between atoms of the backbone

  
• Alpha helix


  • The (C=O) of one amino acid is hydrogen bonded to the amino H (N-H) of an amino acid that is four down the chain
  • This pulls the polypeptide chain into a helical structure that resembles a curled ribbon, with each turn of the helix containing 3.6 amino acids
  • The R groups of the amino acids stick outward from the alpha helix, where they are free to interact

  
• Beta pleated sheet


  • Two or more segments of a polypeptide chain line up next to each other, forming a sheet-like structure held together by hydrogen bonds
  • The hydrogen bonds form between carbonyl and amino groups of backbone, while the R groups extend above and below the plane of the sheet
  • The strands of a beta pleated sheet may be parallel or antiparallel

  
• Tertiary structure of proteins


  The overall three-dimensional structure of a polypeptide, primarily due to interactions between the R groups of the amino acids

  
• Quaternary structure of proteins


  • The association of several protein chains or subunits into a closely packed arrangement
  • Each subunit has its own primary, secondary, and tertiary structure
  • The subunits are held together by hydrogen bonds and van der Waals forces between nonpolar side chains

  
• Any alteration in the structure of the subunits or how they are associated causes marked changes in biological activity
• Naming of a peptide (Primary structure)


  • Glycine (Gly, G)
  • Alanine (Ala, A)
  • Valine (Val, V)
  • Leucine (Leu, L)
  • Isoleucine (Ile, I)
  • Methionine (Met, M)
  • Proline (Pro, P)
  • Phenylalanine (Phe, F)
  • Tryptophan (Trp, W)
  • Serine (Ser, S)
  • Threonine (Thr, T)
  • Asparagine (Asn, N)
  • Glutamine (Gln, Q)
  • Tyrosine (Tyr, Y)
  • Cystine (Cys, C)
  • Lysine (Lys, K)
  • Arginine (Arg, R)
  • Histidine (His, H)
  • Aspartic Acid (Asp, D)
  • Glutamic acid (Glu, E)

  
• Classes of proteins (based on shape)

  • Fibrous Proteins
  • Globular Proteins
  • Intermediate Proteins

  
• Classes of proteins (based on composition)

  • Simple Proteins
  • Conjugated Proteins

  
• Classes of proteins (based on function)

  • Structural proteins
  • Enzymes
  • Hormones
  • Pigments
  • Transport proteins
  • Contractile Proteins
  • Storage proteins
  • Toxic proteins

  
• Draw the amino acid sequence structure of


  Methionyl-Cystyl-Glutaminyl-Threonine