amino acids and protein structure

• translation is the assembly of amino acids into polypeptides
• amino acids contain an amino group and a carboxyl group bonded to a central carbon with a hydrogen group and an R group
• Two amino acids are joined by a covalent peptide bond between the amino and carboxyl groups by a dehydration reaction
• polypeptides are linear chains of amino acids linked by peptide bonds
• in nonpolar amino acids the R groups usually contain a CH2 or a CH3
• in uncharged polar amino acids the R groups usually contain O or OH
• in charged amino acids the R groups contain acids or bases that can ionize
• in aromatic amino acids the R groups contain a carbon ring with alternating single and double bonds
• the special functional amino acids include methionine, proline, and cysteine
• methionine is the first amino acid in a polypeptide
• proline causes kinks in the polypeptide chain
• cysteine is a disulfide bridge that contributes to the structure of polypeptides
• the primary amino acid sequence determine protein folding and the 3D structure that is critical for proper function
• the 2 structure depends on H bonding in the polypeptide backbone. this can be alpha helices or beta sheets
• the 3 structure is the 3D structure of a single polypeptide that is composed of interactions between R groups
• the 4 structure is the interactions between multiple polypeptides to form a multisubunit protein
• protein folding may be disrupted by denaturation, due to heat or chemicals, or mutations
• chaperones protect slow-folding or denatured proteins by preventing their aggregation
• there are 20 common amino acids