Q40.Trypan blue assay is used for the:

(A) Counting of animal cells
(B) Quantification cellular proteins
(C) Quantification of nucleic acid
(D) Identification of metabolite

Trypan blue assay is used for counting animal cells, specifically to assess viability by distinguishing live from dead cells.

This dye exclusion method relies on intact cell membranes of viable cells repelling the dye, while compromised membranes of dead cells allow staining.

Option Breakdown

(A) Counting of Animal Cells

Trypan blue stains dead animal cells blue under microscopy, enabling manual counting via hemocytometer to quantify total and viable cells. It provides rapid viability percentage: (viable cells / total cells) × 100, ideal for cell culture monitoring.​

(B) Quantification of Cellular Proteins

Protein quantification uses assays like Bradford, BCA, or Lowry, measuring color changes from protein-dye binding, not cell membrane integrity.​

(C) Quantification of Nucleic Acids

Nucleic acid quantification employs spectrophotometry (A260) or fluorometric methods like PicoGreen, targeting DNA/RNA absorbance or binding.​

(D) Identification of Metabolites

Metabolite identification involves chromatography (GC-MS, LC-MS) or NMR spectroscopy, analyzing chemical signatures, unrelated to cell viability staining.​

Trypan blue assay is used for the counting of animal cells, a fundamental technique in cell biology labs for viability checks. This MCQ—covering options like protein quantification, nucleic acid measurement, metabolite identification—tests essential knowledge for biology students and researchers.

Principle of Trypan Blue Assay

Live animal cells exclude trypan blue due to intact membranes, appearing clear; dead cells stain blue by dye uptake. Mixed with cell suspension, it’s loaded on a hemocytometer for microscopic counting, calculating viability as unstained cells divided by total.​

Procedure Steps

• Mix equal volumes of cell suspension and 0.4% trypan blue.

• Load onto hemocytometer chamber.

• Count viable (clear) and dead (blue) cells in grids.

• Viability % = [1 – (blue/total)] × 100; adjust for dilution.

Why Not Other Options?

• Cellular Proteins: Requires specific protein-dye assays.​

• Nucleic Acids: Uses UV absorbance or fluorescent dyes.​

• Metabolites: Needs mass spectrometry or chromatography.​

Trypan blue assay is used for the counting of animal cells (A), making it indispensable in microbiology and tissue culture.