Question

9 Interpret your results: a In which tube(s) did protein digestion occur? How do you know? b In which tube(s) did no protein digestion occur? How do you know? c What effect does pH have on protein digestion with pepsin? Why? d What other effects does acid have in the stomach? Procedure 3 Demonstrate Lipid Emulsification Let's examine what happens during the process of emulsification. In this exercise you will use four substances to observe emulsification in action: 1 Lipids: The source of lipids for this exercise is vegetable oil. Emulsifying agent: Detergents are considered to be emulsifiers because they have both polar parts and nonpolar parts, similar to bile salts. The emulsifying agent in this exercise will be a liquid detergent. Distilled water. Sudan red stain: This is a stain that binds only to lipids. The sole purpose of this stain is to make the lipids more visible during the procedure. Safety Note 1 Obtain a glass test tube and add approximately 2 ml. of distilled water to it. Safety glasses and gloves are required! 2 Add about 2 ml. of vegetable oil to the water. 3 Place a rubber stopper into the tube and shake it vigorously for 15 seconds. Allow it to stand for 2 minutes. What happens to the oil and water? А 4 Add three or four drops of Sudan red stain, and shake the tube again for 15 seconds. What color is the oil? What color is the water? 5 Add about 1 ml. of liquid detergent to the mixture and shake the tube vigorously for 15 seconds. Allow the tube to stand for 2 minutes. What has happened to the solution? Is it still two distinct colors? Explain your results.

Answer 1

Answers to the questions in the demonstration given :

Step 3 ) Since oil is non polar and water is a polar molecule, both will not dissolved but remain separated. Moreover since the density of oil is less than that of water, oil will float over water.

Step 4 ) The stain given here is Sudan red stain which binds only to lipids and it helps us identify lipids by making it more visible. Since we've mixed few drops of the stain into the tube so the color of the lipid will stain red and water will remain colorless.

Step 5 ) Now the liquid detergent has been added to the mixture and shaken vigorously. Liquid detergent has a polar hydrophilic head and a non polar hydrophobic tail and will lead to the formation of micelles which will be soluble in water. As the lipid droplets has been covered with hydrophilic heads, they'll be soluble in water and the solution will not have two distinct colours, it'll be uniform throughout the solution.