lab 3: estimation of protein by colorimetric BCA method

1. Why is protein quantification required in biochemistry?

B. Most research requires knowing precise protein concentration

2. One major category of protein quantification techniques is:

B. Colorimetric method

3. Colorimetric methods rely on:

B. Protein-reagent color reaction

4. Color intensity in colorimetric assay is proportional to:

C. Protein concentration

5. A standard calibration curve is used to:

B. Calculate unknown concentration

6. Common colorimetric protein assays include:

B. Bradford, Biuret/Lowry, BCA

7. Mechanism of BCA method begins when:

B. Protein reduces Cu²⁺ to Cu⁺

8. Cu⁺ reacts with BCA reagent to form:

B. Purple complex

9. BCA purple complex is measured at wavelength:

C. 562 nm

10. UV spectrophotometric protein estimation is based on:

A. UV absorption at 280 nm

11. UV absorbance curve compares:

B. Standard proteins vs their 280 nm absorbance

12. Requirements list includes which standard protein?

B. Serum or egg albumin

13. The mixture ratio for BCA reagent is:

C. 50:1

14. First step in BCA assay is preparing:

C. Standard 1 mg/mL protein solution

15. Test tubes 1–10 contain BCA:

B. 10–100 μL standard protein

16. A blank tube contains BCA:

B. 100 µL distilled water

17. Unknown sample tubes are labeled BECAUSE:

C. Unknown A and B

18. Unknown sample volumes used are BCA:

B. 20 and 40 µL

19. Reaction after reagent addition occurs at BCA:

B. 37°C for 30 minutes

20. Absorbance is read using BCA:

B. Colorimeter at 562 nm

21. Standard curve X-axis represents BECAUSE:

B. Concentration of standard protein

22. The principle of colorimetric estimation is BCA:

B. Color intensity ∝ analyte concentration

23. UV absorbance in proteins occurs due to BCA:

A. Aromatic amino acids

24. A colorimetric assay alternative to BCA is:

B. Coomassie Bradford assay

25. Mechanism of BCA involves copper reduction under:

C. Alkaline conditions

26. Beer-Lambert law relates absorbance to:

B. Concentration

27. Unknown protein concentration is found by:

B. Comparing its absorbance to standard curve

28. More purple color formation indicates:

B. Higher protein concentration

29. Graph paper is required to:

B. Plot calibration curve

30. A cuvette is used to:

A. Measure color absorbance