Project 3.2.2Using Chemical Indicators to Test the Presence

of Macromolecules

By: Nicolas Sbrocco

What Is a Chemical Indicator?• Definition: A chemical indicator is a

substance used to show visually usually by it’s capacity for color change, the condition of a solution with respect to the presence of free acid or alkali or some other substance.

• Examples: Benedict’s solution, Iodine, Biuret solution, Sudan 4, Brown paper bag.

How to Test for Monosaccharides

• Procedures:– Fill test tube with 2 milliliters of water.– Add 2 milliliters of Benedict’s reagent to the solution– Heat test tube for 5 minutes– Record the color of the solution– Add glucose solution to the Benedict’s reagent and heat in

boiling water for 5 minutes– Record the color of the solution

• Positive Test: ORANGE• Negative Test: STAYS BLUE

How to Test for Polysaccharides

• Procedures: – Add 2 milliliters of iodine to 2 milliliters of water– Record color of solution– Add 2 milliliters of iodine to a starch solution– Record color of solution

• Positive Test: DARK BLUE/BLACK• Negative Test: STAYS YELLOW

How to Test for Proteins

• Procedures: – Add 2 milliliters of Biuret reagent to 2 milliliters

of water– Record color of the solution – Add 2 milliliters of Biuret reagent to a protein

solution – Record color of the solution

• Positive Test: LAVENDER/PURPLE• Negative Test: STAYS CLEAR

How to Test for Lipids

• Procedures: – Add 2 milliliters of Sudan 4 to 2 milliliters of

water– Record the color of the solution – Add 2 milliliters of Sudan 4 to a oily/fatty solution– Record the color of the solution

• Positive Test: RED• Negative Test: STAYS THE SAME

Another Way to Test for Lipids

• Procedure: – Obtain a brown paper bag– Put 2 drops of water on the bag and record what

happens to the bag after 30 minutes– Put 2 drops of a fatty/oily solution on the bag and

record what happens to the bag after 30 minutes• Positive Test: BAG BECOMES

TRANSLUCENT• Negative Test: BAG STAYS THE SAME