"They are all organic compounds, that is, they contain the element carbon. Carbohydrates and lipids both contain carbon (C), hydrogen (H), and oxygen (0); proteins contain these three elements plus one or more from nitrogen (N), sulphur (S) and phosphorous (P)."
Lipid molecules contain more energy per gram than carbohydrates (about twice as much). Carbohydrates are stored as glycogen in animals while lipids are stored as fats (in plants carbohydrates are stored as cellulose and lipids as oils) Lipids have less effect on osmotic pressure within a cell than complex carbohydrates.