Lab 6 Review : Testing for Macromolecules

List all of the reagents

1.) Benedict's solution (reducing sugars) 2.) Lugol's iodine (complex carbs, polysaccharides) 3.) Biuret reagent (proteins) 4.) Sudan IV (lipids)

Testing for proteins with Biuret Reagent

1.) Label three test tubes - Positive control : + - Negative control : - - Unknown : U 2.) Add 5 drops of protein solution into the positive control tube, 5 drops of water into the negative control tube, and 5 drops of the unknown solution into the U tube. 3.) Add 5 drops of Biuret reagent to all the tubes and mix gently

How to test for complex carbohydrates (starch) with Lugol's iodine

1.) Label three test tubes - Positive control : + - Negative control : - - Unknown : U 2.) Add 5 drops of starch solution in the positive control tube, 5 drops of water into the negative control tube, and 5 drops of the unknown solution into the U tube. 3.) Add 3 drops of Lugol's iodine to all the tubes and mix gently. *Wear gloves and goggles

Testing for lipids with Sudan IV

1.) Label three test tubes - Positive control : + - Negative control : - - Unknown control : U 2.) Add 1 mL of LIPID SOLUTION and 2 mL of WATER into the positive control tube, add 3 mL of WATER into the negative control tube, and 1 mL of the UNKNOWN and 2 mL of WATER into the U tube 3.) Add small amount of Sudan IV to each tube and mix gently 4.) How many layers of liquid are there?

How to test for reducing sugars (glucose) with Benedict's solution

1.) Label three test tubes - Positive control : + - Negative control : - - Unknown: U 2.) Add 5 drops of GLUCOSE into POSITIVE control tube, 5 drops of WATER into NEGATIVE control tube, and 5 drops of unknown solution into the U tube 3.) Add 5 drops of Benedict's solution to each tube. - Mix contents by swirling - Record initial color 4.) Place all tubes in boiling water bath at the same time. - Heat for one minute or until the positive control changes color

How many drops of Lugol's iodine gets added to each tube?

3 drops

How many drops of Benedict's solution gets added to each tube?

5 drops

How many drops of Biuret reagent gets added to each tube?

5 drops

Testing for presence of reducing sugars (glucose)

Benedict's reagent - A clear blue reagent - When heated, the copper in the solution is reduced which causes a color change - Positive test: Green, yellow, light orange, dark orange - Negative test: blue

What test requires heat?

Benedict's solution to test for reducing sugars (glucose)

Testing for proteins

Biuret Reagent - Positive test: purple - Negative test: blue

What color is a negative test with Benedict's reagent?

Blue

What color is a negative test with Biuret reagent?

Blue

What color is a positive test with Lugol's iodine?

Blue-black

What color is a negative test with Lugol's iodine?

Brown or yellow

What is a qualitative test?

Only confirm the absence of presence of a substance

What color is a positive test with Benedict's reagent?

Green, yellow, light orange, dark orange

What a quantitative test?

Helps determine the amount of macromolecule present in the sample

Testing for presence of complex carbohydrates (like starch and glycogen)

Lugol's iodine - Positive test: Blue-black - Negative test: Brown, yellow

What gets added to each tube in the Sudan IV test?

Positive: 1mL lipid solution and 2 mL water Negative: 3 mL of water Unknown: 1 mL of unknown and 2 mL of water

What color is a positive test with Biuret reagent?

Purple

What is a negative test with Sudan IV?

Red dye and water mix

What is a positive test with Sudan IV?

Separation of red dye and water

Testing for lipids (fats and oils)

Sudan IV - Commonly used to help differentiate a lipid layer from a layer of water - Nonpolar red dye attracted to other nonpolar substances - Positive: Separation of red dye and water - Negative: Red dye and water mix

What are control groups?

Tested alongside the experimental group - Positive and negative control - Water typically serves as the negative control - The positive control contains the item being tested for