IDENTIFYING MACROMOLECULES IN

NutrientsLAB

Mrs. StewartMrs. Stewart

Honors BiologyHonors Biology

Lab Objective

Identify the presence of major nutrients such as Identify the presence of major nutrients such as simple carbohydrates (glucose), complex simple carbohydrates (glucose), complex carbohydrates (starch), protein and fat in carbohydrates (starch), protein and fat in

common foods.common foods.

In this lab, with the use of indicators as chemical detection tools, you will analyze a variety of foods for the presence of nutrients.

Detection is based upon observing a chemical change that takes place most often a change in color.

What is an indicator?

• Indicators are chemical compounds used to Indicators are chemical compounds used to detect the presence of other compounds.detect the presence of other compounds.

Test for Simple CarbohydratesBenedict’s solution

• Benedict's solution is a chemical indicator for simple sugars such as glucose: C6H12O6.

• Aqua blue: negative test yellow/green/brick red, etc.: positive test

Benedict’s Test• Benedict’s reagent

undergoes a complex colour change when it is reduced

• The intensity of the colour change is proportional to the concentration of simple sugars present

• The colour change sequence is:– Blue…(negative)– green…– yellow…– orange…– brick red(very positive)

Test for Simple CarbohydratesBenedict’s solution

• Unlike some other indicators, Benedict’s solution does not work at room temperature - it must be heated firstit must be heated first..

QuestionWhy didn’t the test tube containing starch

change colors?

Test for Complex CarbohydratesIodine Solution

• Iodine solution color change = blue to black

Test for Complex CarbohydratesIodine solution

• Iodine solution is an indicator for a molecule called starch.

• Starch is a huge molecule made up of hundreds of simple sugar molecules (such as glucose) connected to each other.

Test for Protein (amino acids)Biuret solution

• Biuret solution dark violet blue to pinkish purple

Test for Fats (lipids)Sudan III

• If lipids are present the Sudan III will stain them reddish-orange (positive test).

INDICATORINDICATOR MACRO-MACRO-MOLECULEMOLECULE

NEGATIVE NEGATIVE TESTTEST

POSITIVE POSITIVE TESTTEST

Benedict’s Benedict’s solutionsolution

simple simple carbohydratecarbohydrate

blueblue Green,Green, yellow, yellow, orange, orange,

brick redbrick red

Iodine Iodine solutionsolution

complex complex carbohydratecarbohydrate

dark reddark red blackblack

Biuret Biuret solutionsolution

proteinprotein blueblue violetviolet, , blackblack

Sudan IVSudan IV lipidlipid dark reddark red reddishreddish- - orangeorange

It’s up to you to save us!

• New type of zombie emerges• They thrive by feeding on

simple sugars• Complex carbs & proteins are

deadly to them

• What will be the best food to combat this threat?– Milk, yogurt or oatmeal?