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.
Carbohydrates: Your Bodyâs Primary Fuel Source. Carbohydrates are your bodyâs main fuel source. There are two types of carbohydrates: simple and complex. Simple carbohydrates are carbs that your body can break down into glucose and burn as energy almost immediately.