As the seed within a barley grain starts to germinate, genes that code for digestive enzymes are switched on. The enzymes produced then catalyse the hydrolysis of storage molecules such as proteins and starch. Explain what is meant by a gene.
The hydrolysis of proteins in the barley seed releases amino acids that can be used to make the proteins needed for the formation of the seedling (young plant). Fig. 2.1 shows an incomplete diagram of the molecular structure of the smallest amino acid, glycine. Each glycine molecule contains two carbon atoms. Complete Fig. 2.1 to show the molecular structure of glycine.
Starch is made up of two different molecules. Name these two molecules.
Table 2.1 lists some of the substances shown in Fig. 2.2. Complete Table 2.1 to show which of the terms polysaccharide, monosaccharide and macromolecule apply to each listed substance. Use a tick (✓) if the term applies and a cross (✗) if it does not. Insert a tick (✓) or a cross (✗) in every box.
Suggest one other advantage of using enzymes from microorganisms instead of enzymes taken from barley seeds in the production of sugar syrups.
Explain the effect of temperature on the activity of $\alpha$-amylase extracted from barley seeds, as shown in Fig. 2.3.
Sketch on Fig. 2.3 the curve that would be produced by a heat-stable $\alpha$-amylase enzyme.