Trans-fat, however, refers to spatial arrangement of the fatty acid molecule (it's 3D shape) - single bonds between carbon atoms are “flexible”, allowing the whole chain to rotate around that bond. Double bonds, however, are rigid. read more
In unsaturated fats, at least one bond between two neighboring atoms of carbon is a double bond with one hydrogen bond for each carbon atom eliminated. Monounsaturated fats have one such double bond, while polyunsaturated fats have two or more double bonds. read more
Fat molecules are made up of hydrogen, oxygen and carbon. When the open slots in a molecule are filled with hydrogen, then the fat is hydrogen saturated - or saturated, for short. Hydrogenation is what makes oil a solid at room temperature, as in the case of margarine, and preserves it longer on store shelves. read more