Grains, seeds, nuts, and root vegetables are types of COMPLEX carbohydrates that require a LONGER time to be broken down, which helps one feel full for an extended period. Complex carbohydrates are polysaccharides made of chains containing hundreds of monosaccharide units, so they take more time to digest completely.
The inability of a cell to take in or produce sugars prevents the synthesis of carbohydrates and nucleic acids.