Fructose is commonly found in fruit. Disaccharides contain two monosaccharides joined by condensation. Sucrose is composed of glucose and fructose and is transported within plants. Lactose is composed of galactose and glucose and is found in milk. Starch is straight chain of glucose molecules with few side branches.
Lipids are varied in structure.
Many are insoluble in water because they lack polar groups. Because the carboxyl group is a polar group, fatty acids are soluble in water. Most fatty acids in cells contain 16 to 18 carbon atoms per molecule. Saturated fatty acids have no double bonds between their carbon atoms. Unsaturated fatty acids have double bonds in the carbon chain.