However, in the form of N2, nitrogen is unusable by all organisms except for a few primitive bacteria that are capable of converting N2 gas to ammonia (NH3). This process of conversion is called nitrogen fixation, and makes the nitrogen available for use by organisms.
1 Simple carbohydrates have very simple chemical structures and are made of small molecules. 2  Complex carbohydrates have very complex structures while the molecules are large, unlike simple carbohydrates.
Carbs 101: Simple vs. Complex. Carbohydrates are made up of sugar molecules, which your body breaks down into fuel, especially when youâre working hard. Sugars, starches, and fiber are all basic forms of the carbohydrate. There are two main types of carbohydrates: simple and complex.