SolutionsFood
1. Starch and cellulose
Starch and cellulose are both made of glucose units. Why can we digest the first but not the second?
Because the glucose units are joined differently: by α-glycosidic bonds in starch and β-glycosidic bonds in cellulose. Our digestive enzymes (amylases) only hydrolyse α bonds.
2. Oil or butter
Why is olive oil liquid at room temperature while butter is solid? What happens when an oil is hydrogenated?
Oil contains mostly unsaturated fatty acids, with cis double bonds that bend the chains and hinder their packing; butter is rich in saturated fats, with straight chains that pack well. Hydrogenating the oil turns the double bonds into single bonds and gives a solid fat (margarine).
3. Fruity aromas
Isoamyl acetate smells of banana. Which family of compounds does it belong to, and which acid and alcohol does it derive from?
It is an ester, derived from acetic acid and isoamyl alcohol (3-methyl-1-butanol).