Red Dye
Introduction
The membrane of a living cell plays a vital role in regulating what goes into and out of the cell. Some characteristics of cell membranes are discovered in this exercise.
Background
The following information is key for the interpretation of the results of this experiment 1. Neutral red is a vital stain. It stains cells without quickly killing them. Many biological stains kill living cells. 2. Neutral red goes through an obvious color change, from red at about pH 6.8 to yellow at pH 8.0. 3. A 1% solution of sodium bicarbonate has a pH of about 8.5. 4. Yeast cells have an internal pH that is slightly acidic (about 5.5 to 6.0).
Concepts
• Diffusion • Active transport
• Acid–base indicators • Selective permeability
Materials
Ammonia solution, NH3
, 0.01 M Beaker, 100-mL
Hydrochloric acid solution, HCl, 0.01 M Filter paper
Neutral red solution, 0.02% Funnel
Potassium hydroxide solution, KOH, 0.01 M Graduated cylinder, 25-mL
Sodium bicarbonate solution, NaHCO3
, 1% Pipets or droppers
Sodium hydroxide solution, NaOH, 0.01 M Test tubes, 13 × 100 mm
Yeast, suspended in 1% NaHCO3 solution Water bath
Safety Precautions
Dilute acids and bases are skin and eye irritants; they are slightly toxic by ingestion and inhalation. Wear chemical splash goggles, chemical-resistant gloves, and a chemical-resistant apron. Please review current Material Safety Data Sheets for additional safety, handling, and disposal information.
Preparation
The concentrations of solutions for this activity do not need to be precise in order for the lab to work. However, the recipes provided do provide consistent results. 1. Sodium bicarbonate solution: Mix 1 g of sodium bicarbonate in 100 mL of distilled or deionized water. 2. Neutral red solution: Mix 0.2 g of neutral red in 1 L of distilled water. 3. Dilute acid solution: Use 0.01–0.1 M hydrochloric acid. 4. Sodium hydroxide solution: Use 0.01 M sodium hydroxide, 0.40 g/L. 5. Potassium hydroxide
The membrane of a living cell plays a vital role in regulating what goes into and out of the cell. Some characteristics of cell membranes are discovered in this exercise.
Background
The following information is key for the interpretation of the results of this experiment 1. Neutral red is a vital stain. It stains cells without quickly killing them. Many biological stains kill living cells. 2. Neutral red goes through an obvious color change, from red at about pH 6.8 to yellow at pH 8.0. 3. A 1% solution of sodium bicarbonate has a pH of about 8.5. 4. Yeast cells have an internal pH that is slightly acidic (about 5.5 to 6.0).
Concepts
• Diffusion • Active transport
• Acid–base indicators • Selective permeability
Materials
Ammonia solution, NH3
, 0.01 M Beaker, 100-mL
Hydrochloric acid solution, HCl, 0.01 M Filter paper
Neutral red solution, 0.02% Funnel
Potassium hydroxide solution, KOH, 0.01 M Graduated cylinder, 25-mL
Sodium bicarbonate solution, NaHCO3
, 1% Pipets or droppers
Sodium hydroxide solution, NaOH, 0.01 M Test tubes, 13 × 100 mm
Yeast, suspended in 1% NaHCO3 solution Water bath
Safety Precautions
Dilute acids and bases are skin and eye irritants; they are slightly toxic by ingestion and inhalation. Wear chemical splash goggles, chemical-resistant gloves, and a chemical-resistant apron. Please review current Material Safety Data Sheets for additional safety, handling, and disposal information.
Preparation
The concentrations of solutions for this activity do not need to be precise in order for the lab to work. However, the recipes provided do provide consistent results. 1. Sodium bicarbonate solution: Mix 1 g of sodium bicarbonate in 100 mL of distilled or deionized water. 2. Neutral red solution: Mix 0.2 g of neutral red in 1 L of distilled water. 3. Dilute acid solution: Use 0.01–0.1 M hydrochloric acid. 4. Sodium hydroxide solution: Use 0.01 M sodium hydroxide, 0.40 g/L. 5. Potassium hydroxide