How spectrophotometry works?

Part 1 - Biomolecule of choice

You will write an essay on a biological molecule, describe which category it fits into (lipid, protein, nucleic acid or carbohydrate) and research how this specific molecule relates to disease. The choice of biomolecule and the associated disease(s) is up to you. More interesting, unusual or rare diseases will score more highly.

In your essay, please discuss:
The chemical structure and function of the biomolecule
The diseases associated with that biomolecule
Make it clear why the molecule/disease you have chosen fits into one of the categories (lipid, carbohydrate, protein or nucleic acid)

Part 2 - The role of spectrophotometry in the laboratory

The essay answers should be constructed coherently, please discuss:

How spectrophotometry works?

Detail how spectrophotometry is used in the laboratory (with examples)

What is the `Beer-Lambert` law?

Detail the key properties of chemical compounds that enable spectrophotometric analysis. What are `experimental controls`? How would these be used in spectrophotometry?