PREP 4 SEMIS

• What is the focus of Experiment 8 in the chemistry lab?

  Color reaction of proteins and amino acids
• What are the methods used to identify proteins?

  • Colloidal reactions (e.g., heat coagulation, salting out)
  • Chemical reactions based on acidity/basicity
  • Specific chemical group reactions (color reactions)
• Which proteins are tested in this experiment?

  Casein and Albumin
• What concentration of amino acids is used in the experiment?

  1% solutions
• What is the purpose of the Ninhydrin Reaction?

  • Detects free amino groups (-NH₂)
  • Indicates presence of amino acids like glycine and alanine
• What is the first step in the Ninhydrin Reaction procedure?

  Neutralize each sample with solid sodium acetate (NaOAc)
• What color change indicates a positive result in the Ninhydrin Reaction?

  A purple-blue color (Ruhemann's purple)
• What happens to free amino acids during the Ninhydrin Reaction?

  They react with ninhydrin, releasing ammonia and forming a purple complex
• What does the Biuret Test detect?

  • Detects peptide bonds (-CO-NH-)
  • Works best with larger proteins like casein and albumin
• What is the procedure for the Biuret Test?

  Mix 1/2 mL of 10% NaOH and add 1-2 drops of 0.5% CuSO₄ solution
• What color indicates a positive result in the Biuret Test?

  A violet color
• How do copper ions react in the Biuret Test?

  Copper ions bind to peptide bonds in an alkaline medium, forming a colored complex
• What is the purpose of the Xanthoproteic Test?

  • Detects aromatic amino acids like phenylalanine, tyrosine, and tryptophan
  • Produces a yellow solution or precipitate upon alkalization
• What is the first step in the Xanthoproteic Test procedure?

  Add 1/2 mL of concentrated nitric acid (HNO₃) to the test sample
• What color change indicates a positive result in the Xanthoproteic Test?

  A yellow solution or precipitate that deepens upon alkalization
• What does the Millon-Nasse Test specifically detect?

  • Detects tyrosine due to its phenolic group
  • Produces a red color upon reaction
• What is the procedure for the Millon-Nasse Test?

  Add 3 drops of Millon’s reagent to the test sample and heat
• What color indicates a positive result in the Millon-Nasse Test?

  A red color
• What is the purpose of the Hopkins-Cole Test?

  • Detects tryptophan
  • Produces a violet ring at the junction of two liquids
• What is the procedure for the Hopkins-Cole Test?

  Add 0.5 mL of Hopkins-Cole reagent and layer with concentrated sulfuric acid
• What indicates a positive result in the Hopkins-Cole Test?

  A violet ring at the junction of the two liquids
• What does the Bromine Water Test detect?

  • Detects tryptophan
  • Produces a colored alcohol layer
• What is the procedure for the Bromine Water Test?

  Add 2 drops of bromine water and shake with n-amyl alcohol
• What are nucleic acids primarily composed of?

  Mononucleotide repeating units
• What color change indicates a positive result in the Bromine Water Test?

  The alcohol layer turns colored (often pinkish to violet)
• What are the two types of nucleic acids?

  DNA and RNA
• What is the purpose of the Pauly Reaction?

  • Detects histidine and tyrosine
  • Produces a red azo dye
• What is the primary function of DNA in cells?

  It serves as the hereditary material
• Where is DNA located in plant and animal cells?

  Within the nucleus
• What is the procedure for the Pauly Reaction?

  Mix cold sulfanilic acid with cold NaNO₂ and add the test sample
• What indicates a positive result in the Pauly Reaction?

  A red azo dye
• What are the three basic steps in the DNA isolation process?

  1. Lysis: Breaking down cell walls/membranes
  2. Precipitation: Separating DNA from debris
  3. Purification: Treatment to precipitate DNA
• What does the Lead Acetate Reaction detect?

  • Detects sulfur-containing amino acids like cysteine and cystine
  • Produces a black precipitate
• What occurs during the lysis step of DNA isolation?

  DNA is released by breaking down cell walls and membranes
• How does precipitation help in DNA isolation?

  It separates DNA from cellular debris using cold alcohol
• What is the procedure for the Lead Acetate Reaction?

  Add 1/2 mL of 20% NaOH and 2 drops of lead acetate to the test sample
• What is the purpose of using concentrated HCl in the purification step?

  To precipitate DNA by exploiting its insolubility
• What color indicates a positive result in the Lead Acetate Reaction?

  A black precipitate
• What does hydrolysis of nucleic acids achieve?

  It breaks nucleic acids into their basic components
• What is the purpose of the Sakaguchi Reaction?

  • Detects arginine
  • Produces a red color