IDENTIFYING MACROMOLECULES

IN FOOD LAB

Warm-up

1.  What are the 4 macromolecules? 2.  What are there monomers? 3.  What is one question that you still have?

When you finish, complete Questions 1-14 of Testing for Biologically Important Molecules (follow the link on my website!)

Introduction

•  Carbohydrates, proteins, and fats are all essential nutrients.

•  We cannot manufacture these nutrients so we must obtain them from our environment.

Introduction •  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 detect the presence of other compounds.

Background Information INDICATOR MACRO-

MOLECULE NEGATIVE

TEST POSITIVE

TEST

Benedict’s solution

simple carbohydrate

blue orange

IKI solution complex carbohydrate

dark red

black

Biuret solution

protein blue

violet, black

Sudan IV

lipid

dark red reddish- orange

Test for Simple Carbohydrates Benedict’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

Test for Simple Carbohydrates Benedict’s solution

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

Test for Complex Carbohydrates Lugol’s solution (Iodine)

•  IKI solution à (Iodine Potassium Iodine) color change = blue to black

Test for Complex Carbohydrates Lugol’s Iodine 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 Fats (lipids) Sudan IV

•  Like lipids, the chemical Sudan IV is not soluble in water; it is, however, soluble in lipids.

•  In this test dark red Sudan IV is added to a solution along with ethanol to dissolve any possible lipids.

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

Test for Fats (lipids) Sudan IV

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

Test for Protein (amino acids) Biuret solution

•  Biuret solution à dark violet blue to pinkish purple

Procedure Simple carbohydrate

1.  Add ~15 drops of monosaccharide to test tube labeled Mono.

2.  Add ~15 drops of disaccharide to test tube labeled Disac.

3.  Add ~15 drops of polysaccharide to test tube labeled Poly.

4.  Add ~15 drops of water to the test tube labeled H2O

5.  Add 10 drops of Benedict solution 6.  Place test tube in a hot water bath for 5 min

–  Record your results

Procedure Complex carbohydrate

1.  Add ~15 drops of monosaccharide to test tube labeled Mono.

2.  Add ~15 drops of disaccharide to test tube labeled Disac.

3.  Add ~15 drops of polysaccharide to test tube labeled Poly.

4.  Add 10 drops of IKI solution to each test tube

–  Record your results

Procedure Protein (amino acids)

1.  Add ~15 drops of known protein sample to well-tray

2.  Add ~15 drops of known non-protein (any of the other samples in the front of the room) to well-tray

3.  Add 10 drops of Biuret solution –  Record your results

Procedure Fats (lipids)

•  Using a Q-Tip smear a sample of the lipid onto a square of brown paper.

–  Record your results