Identify, by marking with asterisk (*) symbols, all chiral carbon atoms in the molecules of leucine, isoleucine, valine, proline, and threonine (sub-topic B.2, table 1). Remember that some amino acids contain more than one chiral centre.

The structures of vitamin $\mathrm{C}$ and the preservatives $2-\mathrm{BHA}$ and $\mathrm{BHT}$ are shown in figure $17$.

Determine any chiral carbon atoms in these three compounds by placing an asterisk, *, beside them on a copy of the figure.

The monosaccharide $\mathrm{D}-$fructose is sweeter than $\mathrm{D}-$glucose, so it can be used in smaller amounts in foods. Identify the stereoisomer ($\mathrm{\alpha }-$ or $\mathrm{\beta }-$) of the cyclic forms of glucose and fructose in figure $18$.