Biochemistry Lab Post-Laboratory Assessment Part 1 PDF

Centro Escolar University Physical Sciences and Mathematics, School of Science and Technology 2nd Semester, School Year 2023–2024 POST-LABORATORY ASSESSMENT (PART 1) BIOCHEMISTRY LABORATOR...

Centro Escolar University Physical Sciences and Mathematics, School of Science and Technology 2nd Semester, School Year 2023–2024 POST-LABORATORY ASSESSMENT (PART 1) BIOCHEMISTRY LABORATORY MULTIPLE CHOICE: Choose the BEST answer. Write the letter of your choice in the appropriate box. USE CAPITAL LETTERS ONLY. 1. In the solubility test for lipids, which of the following solvents dissolved olive oil, butter, coconut oil, and lard? A. Water D. Diethyl ether B. 5% HCl E. None of the above C. 5% NaOH 2. Which of the following lipids is classified as a triglyceride with a high content of saturated fats? A. Olive oil D. Lanolin B. Butter E. Lard C. Coconut oil 3. In the iodine test for lipids, which sample reacted the slowest with iodine, indicating a high level of saturation? A. Coconut oil D. Lard B. Olive oil E. None of the above C. Butter 4. Which of the following tests detects the presence of cholesterol based on the formation of a reddish color solution? A. Salkowski's test D. Biuret test B. Liebermann-Burchard test E. Ninhydrin test C. Acrolein test 5. In the Liebermann-Burchard test, which sample gave a positive result, indicating the presence of sterols like cholesterol? A. Cholesterol D. Margarine B. Butter E. Both a and b C. Coconut oil 6. Which of the following tests detects the presence of glycerol by producing a pungent smell upon heating? A. Salkowski's test D. Biuret test B. Liebermann-Burchard test E. Ninhydrin test C. Acrolein test 7. In the Biuret test for proteins, which sample gave a negative result, indicating the absence of peptide bonds? A. Gelatin D. Protein hydrolysate B. Egg albumin E. Both c and d C. Glycine 8. Which of the following tests detects the presence of free amino groups in amino acids and peptides? A. Biuret test D. Millon's test B. Ninhydrin test E. Test for SH C. Hopkins-Cole test 9. In the Hopkins-Cole test, which sample gave a negative result, indicating the absence of tryptophan residues? A. Egg albumin C. Gelatin E. Protein hydrolysate B. Casein D. Tryptophan 1 10. Which of the following tests specifically detects phenolic compounds where the hydroxyl group is directly attached to the benzene ring? A. Biuret test C. Hopkins-Cole test E. Test for SH B. Ninhydrin test D. Millon's test 11. In the test for SH groups, which sample is expected to give a positive result (black precipitate) due to the presence of cysteine residues? A. Albumin C. Casein E. None of the above B. Tyrosine D. Both a and c 12. Which of the following is a common factor that can cause the denaturation of proteins by disrupting their native three-dimensional structure? A. Heat D. All of the above B. Chemical reagents E. None of the above C. Organic solvents 13. In the heat denaturation of proteins, which sample is expected to remain soluble and not undergo significant denaturation? A. Egg albumin D. Both b and c B. Gelatin E. None of the above C. Casein 14. Which of the following reagents is expected to form an insoluble precipitate when reacted with egg albumin? A. Lead acetate D. Trichloroacetic acid (TCA) B. Picric acid E. All of the above C. Tannic acid 15. In the reaction with ethanol, which concentration is expected to cause denaturation and precipitation of egg albumin? A. 95% ethanol C. 40% ethanol E. None of the above B. 70% ethanol D. Both a and b 16. Which of the following tests detects the presence of cholesterol based on the formation of a green color complex? A. Salkowski's test D. Biuret test B. Liebermann-Burchard test E. Ninhydrin test C. Acrolein test 17. In the Ninhydrin test, which sample gave a positive result? A. Egg albumin B. Protein hydrolysate C. Gelatin D. Alanine E. Both b and d 18. Which sample is expected to give a positive result (blue-violet color) in the Hopkins-Cole test, indicating the presence of tryptophan residues? A. Egg albumin D. Tryptophan B. Casein E. Both a and b C. Gelatin 19. In the heat denaturation of proteins, which sample is expected to undergo denaturation and form an insoluble precipitate or coagulated mass? A. Egg albumin C. Casein E. None of the above B. Gelatin D. Both a and c 2 20. Butter is classified as: A. A triglyceride D. A saturated fat B. An emulsion of water and lipids E. A monounsaturated fat C. A sterol alcohol 21. A positive result in the Liebermann-Burchard test is indicated by: A. Blue color C. Green color E. Yellow color B. Red color D. Purple color 22. The test for sulfhydryl (-SH) groups is performed using: A. Lead acetate and NaOH D. Millon's reagent B. Ninhydrin E. Hopkins-Cole reagent C. Biuret reagent 23. Protein denaturation occurs when: A. The primary structure is altered B. The secondary structure is altered C. The tertiary and quaternary structures are disrupted D. The amino acid sequence is changed E. The peptide bonds are cleaved 24. Heat can cause protein denaturation by: A. Providing energy to disrupt weak interactions stabilizing the protein structure B. Breaking peptide bonds C. Altering the amino acid sequence D. Changing the primary structure E. Modifying the secondary structure 25. Which sample would denature upon heating? A. Gelatin C. Glucose E. Urea B. Egg albumin D. Glycine 26. Chemical denaturation of proteins can be achieved by: A. Addition of lead acetate D. Addition of Millon's reagent B. Addition of ninhydrin E. Addition of Hopkins-Cole reagent C. Addition of Biuret reagent For questions 27–40, refer to the following structures: O A E OH O B OH H O H H HO C OH O O D O O OH 27. Which of the substances is a steroid derivative? 28. Which of the substances is an omega-9 fatty acid? 29. Identify from the given compounds an example of a polyunsaturated fatty acid. 30. Which compound is a diglyceride derivative? 31. 18:2, Δ!,#$ 32. Which of the substances has an ester bond? 33. Identify the saturated fatty acid from the given list. 34. Which compound will test positive for the acrolein test? 35. Which of the substances will give positive results to the Salkowski test? 36. Which compound will decolorize iodine the fastest? 3 37. Which of the given substances is a trans fatty acid? 38. Which of the given substances is a cis fatty acid? 39. Which of the given substances is most probably a component of biological membranes? 40. Which of the substances will generate the greatest number of sodium salt or soap molecules upon treatment with concentrated sodium hydroxide? For questions 41–50, refer to the following polypeptide: 41. How many peptide bonds are present in the polypeptide structure given? A. six B. seven C. eight D. nine E. ten 42. How many amino acid residues are present in the structure given? B. six B. seven C. eight D. nine E. ten 43. Which amino acid is the N-terminal residue? A. Arg B. Asp C. Phe D. Met E. Val 44. Which amino acid is the C-terminal residue? A. Asn B. Asp C. Phe D. Met E. Val 45. Which of the following amino acids is NOT present in the polypeptide? A. His B. Trp C. Ser D. Cys E. Tyr 46. Identify the fifth (5th) amino acid residue from the N-terminus. A. S B. C D. R E. Y E. W 47. The polypeptide will not test positive for which of the following? A. Millon’s test D. Hopkins Cole test B. Biuret test E. None of the above C. Lead Acetate test 48. An amino acid residue is present three times (thrice) in the polypeptide. Which amino acid is it? A. Glu D. Met B. Arg E. Gly C. Cys 49. Which of the following is not present in the polypeptide? A. phenol C. sulfhydryl group E. indole B. guanidino group D. imidazole 50. What is the NET charge of the polypeptide? A. +1 B. –2 C. 0 D. +2 E. –4 END OF EXAM 4