An experiment was carried out by the student to investigate the ability of reducing sugars to diffuse through Visking tubing. Fig. 6.2 shows the apparatus used.
Fig. 6.2
At the start of the experiment, the external solution did not contain any reducing sugars.
At intervals, the student tested for the presence of reducing sugars, both within the Visking tubing and in the external solution.
Name the reagent that is used to test for the presence of reducing sugars.
Saccharomyces cerevisiae is a unicellular fungus that is important in the brewing and baking industries.
Fig. 4.1 is a diagram of a transmission electron micrograph of S. cerevisiae.
Fig. 4.1
One function of the lipid droplets shown in Fig. 4.1 is to store triglycerides.
The triglycerides in a lipid droplet are surrounded by a single layer (monolayer) of phospholipids.
Suggest and explain why phospholipids, rather than triglycerides, are used for the outer monolayer of the lipid droplet.
A disaccharide, trehalose, is a reserve store of energy for S. cerevisiae when glycogen stores decrease. The monomer of glycogen and trehalose is -glucose.
Complete Fig. 4.2 to show the ring structure of one -glucose molecule.
Fig. 4.2
A student carried out tests on a solution of trehalose and correctly concluded that trehalose is a non-reducing sugar.
Outline the procedure carried out by the student and state the results that were obtained.
Starch molecules are the main storage molecules in many types of cereal grain, such as the grain of the barley plant.
When the seed inside a barley grain germinates, genes coding for digestive enzymes are switched on. The enzymes that are synthesised catalyse the hydrolysis of storage molecules such as proteins and starch.
The hydrolysis of proteins in the barley seed produces amino acids that can be used in the synthesis of the proteins required for formation of the seedling (young plant).
Fig. 2.1 is an incomplete diagram of the molecular structure of the smallest amino acid, glycine. Each molecule of glycine has two carbon atoms.
Fig. 2.1
Complete Fig. 2.1 to show the molecular structure of glycine.
Starch is a mixture of two different molecules.
Name these two molecules.
Two of the enzymes synthesised by the barley seed are -amylase and maltase. These are involved in the hydrolysis of the stored starch during seedling formation.
In the food industry, the starch extracted from barley seeds (barley starch) is used in the production of sugar syrups. Fig. 2.2 summarises the reactions catalysed by -amylase in the production of maltose syrup and by maltase in the production of glucose syrup.
Fig. 2.2
Some of the substances shown in Fig. 2.2 are listed in Table 2.1.
Complete Table 2.1 to identify which of the terms polysaccharide, monosaccharide and macromolecule apply to each of the substances listed.
Use a tick if the term applies and a cross (x) if the term does not apply.
Put a tick or a cross (X) in every box.
Table 2.1
When producing sugar syrups, there are advantages in using enzymes extracted from microorganisms.
For example, some enzymes extracted from microorganisms are heat stable. Heat-stable enzymes are used to increase productivity because the reactions can be carried out at higher temperatures.
Fig. 3.1 is a transmission electron micrograph showing two adjacent cells in a leaf.
Fig. 3.1
Cellulose is the main polysaccharide in cell walls of plants.
Describe the structure of cellulose.
Fig. 3.2 shows two water molecules linked by a hydrogen bond.
Fig. 3.2
Explain how hydrogen bonding occurs between water molecules.
Suggest why water is an excellent solvent for ions.