Biochemical Tests for Food Molecules

The video tutorial covers a core practical on using chemical reagents to identify starch, reducing sugars, proteins, and fats in food samples. It explains the digestion process and the role of biological molecules in nutrition. The tutorial provides detailed procedures for conducting tests for starch, reducing sugars, proteins, and fats, using iodine solution, Benedict's reagent, Biuret solution, and the emulsion test, respectively.

What happens to the food molecules after they are digested in the body?

• They are converted into water.

• They are excreted as waste.

• They are absorbed into the blood and used to build cells and tissues.

• They remain in the stomach indefinitely.

Which of the following is NOT a main biological molecule found in food?

• Carbohydrates

• Lipids

• Proteins

• Vitamins

What color change indicates the presence of starch when using iodine solution?

• Red to yellow

• Purple to pink

• Blue to green

• Yellow orange to blue black

Which reagent is used to test for reducing sugars?

• Iodine solution

• Biuret solution

• Benedict's reagent

• Ethanol

What color does Benedict's reagent turn if a high amount of reducing sugar is present?

• Brick red

• Orange

• Blue

• Green

What is the initial color of Biuret solution before testing for proteins?

• Yellow

• Purple

• Red

• Blue

What indicates the presence of proteins when using Biuret solution?

• A change to green

• A change to lilac or purple

• A change to red

• A change to blue

What is the purpose of adding ethanol in the emulsion test for fats?

• To neutralize the sample

• To dissolve the fat

• To change the color of the solution

• To heat the sample

What forms if fats are present in the emulsion test?

• A blue solution

• A solid precipitate

• A cloudy emulsion

• A clear solution

Which test does not require heating?

• Starch test

• Reducing sugars test

• Protein test

• None of the above