Question

How do functional groups affect the structure and function of macromolecules?

Answer 1

Specific substituents or moieties within molecules that are responsible for characteristic chemical reactions of those molecules are functional groups. Regardless of the size of molecule, the same functional group will undergo similar chemical reactions.

Complete answer:
Before we move forward with the solution for the given question, let us first understand some important basic concepts. Organic chemistry is basically the chemistry of carbon compounds. The most commonly used elements in organic chemistry are carbon and hydrogen. These elements form chain and ring - based structures to form compounds. The electronic configuration of these elements aids them in their flexible bonding capabilities. Along with being bonded as atoms, there are situations wherein there are either positive or negative sites available on these molecules in the form of a carbocation or a carbanion.
When these sites are formed on these molecules, there is a chance for other chemical substituents to get linked with the given organic compound via the bonding site. These chemical substituents bring new properties to the organic compound and aid in the forming of various other substituent organic compounds. These chemical substituents are known as functional groups. Functional groups are basically groups of one or more atoms of distinctive chemical properties irrespective of the molecule they are attached to.
Functional groups affect the bonds that hold a macromolecule together. For example, the ring forms of glucose in starch and cellulose have different configurations. As a result, cellulose and starch serve different purposes. Functional groups also affect the polarity of the bonds. Lipids consist of hydrophilic heads (red) and hydrophobic tails (black and white). This characteristic of lipids allows them to form bilayers, which serve as membranes of cells.

Note:
Functional groups can also be charged, e.g. in carboxylate salts, which turns the molecule into a polyatomic ion or a complex ion. Functional groups binding to a central atom in a coordination complex are called ligands.