IDENTIFYING MACROMOLECULES Indicators In this lab you will

IDENTIFYING MACROMOLECULES

Indicators In this lab, you will use indicators as chemical detection tool. Indicator- something that can be used to show if a substance is present in a solution. Detection is based upon observing a chemical change; most often a change in color.

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

INDICATOR Background Information MACRO-MOLECULE Glucose strips Simple carbohydrate Benedict’s solution simple carbohydrate Iodine solution complex carbohydrate Biuret solution protein Sudan IV lipid Paper Towel lipid NEGATIVE TEST POSITIVE TEST

Test for Simple Carbohydrates Glucose Strips e tiv ga Ne • Small disposable strips of plastic, with an indictor on the end, used to detect simple sugars such as glucose: C 6 H 12 O 6. • Aqua blue: negative test; ve • Green to brown: positive test is ti o P ive t ga Ne ve Po i sit

Test for Simple Carbohydrates Benedict’s solution • Benedict's solution is a chemical indicator for simple sugars such as glucose: C 6 H 12 O 6. • Aqua blue: negative test; • Yellow/green/brick red, etc. : positive test P it os ive g Ne e v ati

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.

DEMO

Test for Complex Carbohydrates 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 Complex Carbohydrates Iodine Solution • Iodine solution color change = blue to black (positive)

DEMO

Question: Benedict’s Solution Why didn’t the test tube containing sucrose change colors?

Question Benedict’s Solution Why didn’t the test tube containing starch change colors?

Benedict’s Test • Benedict’s reagent undergoes a complex colour change • The intensity of the colour change is proportional to the concentration of sugar present • The colour change sequence is: – – – Blue… no sugar green… very little sugar yellow…little sugar orange…sugar brick red. . . high sugar concentration

Test for Protein (amino acids) Indicator is Biuret solution • Biuret solution dark violet blue to pinkish purple (positive)

DEMO

Test for Fats (lipids) Sudan IV • If lipids are present the Sudan IV will stain them reddish-orange (positive test). e Po iv sit g Ne e v ati

Test for Fats (lipids) Paper Towel Test • If lipids are present they will not evaporate on a paper towel as compared to water.

DEMO

Background Information INDICATOR MACROMOLECULE NEGATIVE TEST POSITIVE TEST Glucose Strips simple carbohydrate Aqua blue (pale blue) Green to Brown color Benedict’s solution simple carbohydrate Pale blue Red, yellow, orange, green Iodine solution complex carbohydrate Yellow- browndark red Purple, black Biuret solution protein Aqua blue violet, dark blue Sudan IV lipid Clear- pale red Red Paper Towel lipid Evaporates Remains Present