Amino Acids, Proteins and DNA

• What is the general structure of an α amino acid?

  NH2, CH, CO2H, R
• What distinguishes glycine from other amino acids?

  Glycine has R as an H
• Why are all amino acids except glycine chiral?

  They have four different groups around C
• What do amino acids do to plane polarized light?

  They rotate it
• What are acidic and basic amino acids characterized by?

  Extra carboxylic acid or amine group
• What is the IUPAC name for aspartic acid?

  1. aminobutanedioic acid
• What is the IUPAC name for glycine?

  1. aminoethanoic acid
• What is the IUPAC name for lysine?

  2,6-diaminohexanoic acid
• What form do amino acids exist in?

  As dipolar zwitterions
• Why do amino acids have relatively high melting points?

  Due to ionic interactions of zwitterions
• What is the acidity and basicity of amino acids attributed to?

  The amine group is basic, carboxylic acid is acidic
• How do amino acids act as buffers?

  They gradually change pH with acid or alkali
• What happens to the extra groups on the R group in different pH conditions?

  They react and change form
• What does the alpha in ‘α’ amino acid signify?

  NH2 and COOH groups on the same C
• What are dipeptides?

  Combination of two amino acids with one amide link
• How many combinations can two different amino acids form in a dipeptide?

  Two possible combinations
• What reactions can the carboxylic acid and amine groups in amino acids undergo?

  Usual reactions of these functional groups
• What happens to proteins when heated with concentrated hydrochloric acid?

  They can be hydrolyzed into amino acids
• How can the composition of a protein molecule be deduced?

  Using TLC chromatography
• What is the method for thin-layer chromatography of amino acids?

  1. Draw a pencil line on TLC plate.
  2. Add drops of each sample.
  3. Place in solvent chamber.
  4. Remove when solvent reaches 1 cm from top.
  5. Spray with ninhydrin and heat.
  6. Calculate Rf values.

  
• What is the significance of Rf values in chromatography?

  Each amino acid has a unique Rf value
• Why is ninhydrin used in amino acid chromatography?

  To visualize transparent amino acids
• What happens to amino acids when ninhydrin is sprayed and heated?

  Red to blue spots appear
• What is the primary structure of proteins?

  Sequence of 20 different amino acids
• What is the secondary structure of proteins?

  α-helix and β-pleated sheet

  
• How are hydrogen bonds involved in protein structure?

  They stabilize α-helices and β-sheets

  
• What is the tertiary structure of proteins?

  Folding of secondary structure into complex shapes

  
• What holds the tertiary structure of proteins in place?

  Interactions between R-side groups of amino acids
• What is the primary structure of proteins?

  Sequence of 20 amino acids linked by peptides
• What are the two types of secondary structures in proteins?

  • α-helix
  • β-pleated sheet

  
• Where do the R-groups point in an α-helix structure?

  Outwards from the helix
• How is the β-pleated sheet structure formed?

  Protein chain folds into parallel strands
• What holds the β-pleated sheet structure in place?

  Hydrogen bonds between amino acids

  
• What interactions stabilize the tertiary structure of proteins?

  Hydrogen bonds, sulfur-sulfur bonds, ionic interactions
• How can hydrogen bonds form in a protein's tertiary structure?

  Between serine side chains in different parts
• What are ionic interactions in proteins?

  Formed between acidic and basic amino acids
• What is a sulfur bridge in proteins?

  Covalent bond between two cysteine side chains
• What are enzymes?

  Proteins that catalyze biochemical reactions
• What is the active site of an enzyme?

  Hollow in the globular protein structure
• What interactions occur at the enzyme's active site?

  Hydrogen bonding, van der Waals forces, ionic interactions