You are given four test tubes containing purified biological macromolecules. The test tubes are unlabeled except for a number between 1 and 4. You are told that one test tube contains a protein, one contains a lipid, one contains a carbohydrate, and one contains a nucleic acid. You then perform some tests on the macromolecules and collect the following information: 1) Test tubes #2 and #4 contain nitrogen, but the other tubes do not.

2) The contents of test tube #3 are not soluble in water, but the contents of the other test tubes are soluble in water.

3) The contents of test tube #1 can be broken down into subunits that are all exactly identical to each other.

4) The macromolecule in test tube #2 is found to have a globular shape.

What are the identities of the macromolecules present in the four test tubes?

#1:carbohydrate

#2:protein

#3:lipid

#4:nucleic acid

Explanation:

1)  Test tubes #2 and #4 contain nitrogen, but the other tubes do not.

->we can infer that Tube #2 and #4 are amino acid(protein) and nucleic acid, because there is nitrogen amine group of protein and nitrogenous sugar base in nucleic acids.

->That means Tube #1 and # 3 are carbohydrates and lipid (actually some could have nitrogen).

2) The contents of test tube #3 are not soluble in water, but the contents of the other test tubes are soluble in water.

->We can infer that Tube # 3 is lipid, because lipids has long hydrocarbon chains often without hydrogen bonding(making it insoluble in water most of the time)

->We can then infer that Tube # 1 is carbohydrate

3) The contents of test tube #1 can be broken down into subunits that are all exactly identical to each other.

->We already know that Tube #1 is carbohydrate already which can be gone through hydrolysis reaction to divide to monosaccharides (this also can be somewhat not true because different monosaccharides can be linked).

4) The macromolecule in test tube #2 is found to have a globular shape.

->uncondensed DNA in A-,B-,Z- form will generally look like double helix. So we can infer that Tube #2 has protein(that are folded like "globular" tertiary and quaternary structure. Making #4 remaining nucleic acid

a symbiotic relationship with the mitochondria