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.
There are three main types of carbohydrates: 1. Simple carbohydrates (sugars): Sugar is the simplest form of carbohydrate. Simple carbs can be digested very quickly. Examples are cereals, honey, molasses, brown sugar, soft drinks, sweets snack bars, corn syrup, male syrup, biscuits, cakes. 2.