Functional groups are special groups of atoms found in molecules. They help decide how those molecules will react in different situations. Here’s a simpler look at their effects on organic molecules:

1. Polarity and Solubility:

   • Functional groups like hydroxyl ($-OH$), carboxyl ($-COOH$), and amino ($-NH_2$) usually make organic compounds more polar. This means they mix well with water and other polar substances.
   • For instance, alcohols (which have the $-OH$ group) dissolve better in water than alkanes, thanks to something called hydrogen bonding.

2. Reactivity:

   • Different functional groups react in different ways.
   • For example, carbonyl groups ($-C=O$) can take part in reactions called nucleophilic additions. Meanwhile, carboxylic acids can react in acid-base reactions.
   • How these groups react often depends on how strongly the atoms within them attract electrons.

3. Biological Activity:

   • Functional groups are super important in biology. For example, esters and amides help make up the structure of fats and proteins.
   • In fact, around 70% of all medicines contain at least one functional group that’s really important for how the medicine works in the body.

Knowing about functional groups helps us understand how organic molecules act in different reactions and how they work in living things.