Katie will use the black, red and purple balls in a ratio 1:2:1 for carbohydrate molecules.
There are four macro molecules in existence, these are carbohydrates, proteins, fat and oil and nucleic acids. All these molecules has carbon in their compounds. The carbohydrate is made up of the elements carbon, hydrogen and oxygen in the ratio 1: 2: 1, thus, the molecular formula of carbohydrate is C6H12O6.