Unit 3: Cell Viability Assay - Practice Quiz

1 What does the MTT assay primarily measure?

2 What does MTT stand for?

3 What color is the MTT reagent before it is reduced by viable cells?

4 What colored product is formed during the MTT assay?

5 Which cells can reduce MTT to formazan?

6 What instrument is commonly used to measure the color produced in an MTT assay?

7 What does higher absorbance generally indicate in an MTT assay?

8 Why are untreated cells often included in an MTT assay?

9 What is the purpose of a blank well in an MTT assay?

10 What happens to MTT in viable cells?

11 Why is a solvent added after formazan crystals form?

12 Which type of plate is commonly used for an MTT assay?

13 What is usually removed before adding the solvent to dissolve formazan?

14 A decrease in MTT absorbance after treatment most likely suggests what?

15 What is a major limitation of the MTT assay?

16 What does a cell viability percentage compare?

17 Why are replicate wells used in an MTT assay?

18 Which result usually indicates greater cell viability?

19 What is the main role of cellular enzymes in the MTT assay?

20 What should be kept consistent between control and treated wells?

21 What cellular property is primarily measured by the MTT assay?

22 Why does the MTT reagent change from yellow to purple during the assay?

23 A treatment produces an absorbance of 0.42, while untreated cells produce 0.70 after blank subtraction. What is the approximate percentage viability?

24 What is the main purpose of wells containing medium and MTT but no cells?

25 Why is a solvent such as DMSO added after MTT incubation?

26 Which wavelength is commonly used to measure dissolved formazan in an MTT assay?

27 A compound is strongly colored at the MTT measurement wavelength. What is the most appropriate control?

28 If cell density is increased beyond the linear range of the assay, what result is most likely?

29 Why are untreated control wells included in an MTT experiment?

30 A positive cytotoxicity control is included mainly to confirm that:

31 Why should the MTT incubation time be kept consistent between experimental wells?

32 What is a likely consequence of incomplete dissolution of formazan crystals?

33 A treatment lowers MTT absorbance but does not reduce cell number. Which interpretation is most appropriate?

34 Why should treatment solvent concentration be identical in control and treatment wells?

35 What is the best reason for using technical replicate wells in an MTT assay?

36 A compound causes a concentration-dependent decrease in relative MTT viability. What does this pattern generally suggest?

37 Why should edge wells sometimes be avoided or filled with sterile buffer in an MTT plate?

38 Which calculation is most suitable for reporting treatment effects relative to an untreated control after blank correction?

39 What is the main advantage of measuring absorbance at a wavelength near the formazan maximum?

40 A sample has a blank-corrected absorbance higher than the untreated control. Which conclusion is most justified?

41 A compound reduces MTT absorbance by 40% after 24 hours, but microscopic inspection shows unchanged cell number and morphology. Which conclusion is most justified?

42 A 96-well MTT experiment produces high absorbance in untreated wells but also substantial absorbance in wells containing medium, MTT, and drug without cells. What is the most appropriate response?

43 Untreated wells have an average corrected absorbance of , while treated wells have . The corresponding cell-free treated blanks have absorbance . Assuming the untreated blank is negligible, what is the estimated viability?

44 A researcher uses a single untreated well as the denominator for all treatment groups, although untreated replicate wells vary substantially. Which analysis is most defensible?

45 In a dose-response experiment, absorbance increases with dose at low concentrations and then declines at higher concentrations. Which interpretation is most scientifically appropriate?

46 Why is it problematic to compare MTT absorbance values obtained from two cell lines without first establishing comparable calibration ranges?

47 The standard curve relating cell number to MTT absorbance is linear from to cells but plateaus above cells. How should samples above the linear range be handled?

48 A hydrophobic test compound precipitates after MTT addition and increases turbidity at the measurement wavelength. Which control is most important for identifying this artifact?

49 After adding the solubilization solution, a plate contains visible purple crystals and large well-to-well variation despite careful pipetting. Which procedural change is most likely to improve measurement reliability?

50 A treatment causes cells to detach from the plate. The investigator washes the wells before adding MTT and reports the remaining signal as viability. What bias is most likely?

51 A solvent used for the test compound reduces cell viability by 15% at its working concentration. Which design best isolates the compound effect?

52 A compound is strongly colored at the MTT measurement wavelength but does not react with MTT. Which result could occur if cell-free compound blanks are omitted?

53 A treatment reduces absorbance but increases the amount of total cellular protein per surviving cell. Why might MTT results disagree with a cell-counting assay?

54 In a 96-well plate, wells at the perimeter show systematically lower absorbance than interior wells in every treatment group. What is the most likely experimental concern?

55 A cytotoxic treatment produces an MTT viability of , but a membrane-integrity assay gives viable cells. Which explanation best accounts for the discrepancy?

56 A positive-kill control gives nearly the same absorbance as the medium blank. What does this primarily indicate about the assay?

57 A plate reader reports absorbance values above the validated upper limit for several untreated wells. Which action is most appropriate before interpreting treatment effects?

58 A treatment is tested in six wells on one plate, and the experiment is repeated on three separate days. Which description correctly distinguishes the replicates?

59 A compound is reported to have an MTT half-maximal inhibitory concentration of . Which statement is the most cautious interpretation?

60 A researcher subtracts the average medium blank from every well but ignores that the test compound has a different blank absorbance. What is the principal analytical error?