Write a short paragraph to explain why the sugar could get through the membrane, but the starch could not?

Basically the starch is too fat and the sugar is small enough of a molecule

Selective permeability. When many glucose molecules combine they form one large molecule called starch. Due to starch being a larch molecules they have difficulty passing through the membrane. Glucose molecules are smaller in size therefore they can pass easily through the membrane.

Explanation:

Selective permeability the the process whereby the cell membrane allows for selective molecules to pass through its membrane, in order to obtain internal equilibrium.