Finding the Unknown Macromolecules
Positive Controls
Benedict’s Test – Sugar – After the Benedict’s test was conducted with the droplets of sugar solution, the solution became a thick, grainy orange brown solution, which was not associated the products of the other solutions after the Benedict’s test. The reason behind this is when Benedict’s solution is mixed and heated with a sugar, which has electrons available to donate, the copper (II) will be reduced to copper (I), which turns it brownish-orange.
Iodine Test – Starch – When the Iodine solution is added to the starch solution, it produces a black solution, while the other macromolecules produce an orange solution with the Iodine solution. The reason why starch is a positive control for the Iodine test is because it contains Amylose. The iodine molecules slip into the Amylose coil, producing a deep blue/black tint.
Biuret Test – Protein – When the Biuret solution is added to the protein solution, it produces a purple solution, while all the other macromolecules with the Biuret solution produce a blue tinted solution. The purple solution comes from the reduction of Cu in the Biuret solution. The only reason proteins can do this is because proteins have more than two peptide bonds.
Sudan IV test – Lipid – After the Sudan IV solution is added in the lipid solution, it separates the solution, leaving a deep red hue. The other macromolecules were pink when they reacted with the Sudan IV solution. The reason to these results is because Sudan IV is soluble in lipids. In will produce a deep red/orange hue in lipids, while sinking in the other macromolecules/water.
Part Two Results
Unknown #
Benedict’s
Iodine
Biuret
Sudan IV
20
Thick green
“fungus-like”
Black/dark purple
Milky light blue at top/deep blue at bottom
Slightly cloudy red
1
Milky orange-yellow
Light brown/orange
Separated light blue top/deep blue at bottom
Thin pink
22
Milky orange-yellow
Dark brown/blackish
Light purple
Light clear pink
Part Two Analysis
Unknown #20 – From the Benedict’s test, it can be concluded that the unknown has some simple sugars in it. Although it doesn’t turn orange, research shows that the solution should progress in the colors of blue, green, yellow, orange, red, and then brick red or brown if the solution has sugar in it while doing the Benedict’s test. From the Iodine test, it can be concluded that the unknown also contains starch in it, as it turns black/dark purple like the positive control. The Biuret Test displayed a light/dark blue solution. However, it wasn’t purple, so the unknown doesn’t contain proteins in it. The Sudan IV test displayed a slightly cloudy red solution, meaning some to most of the Sudan IV solution dissolved in the solution. This means the unknown contains lipids.
Unknown #1 – The Benedict’s test with the unknown produced a orange-yellow solution, meaning the unknown contains simple sugars. The Iodine test with the unknown produced a light brown/orange colored solution. It wasn’t dark enough to conclude that starches were contained in the unknown. The Biuret test with the unknown produced a separated light/dark blue solution like Unknown #20. It wasn’t purple, so the unknown