Enzymes are globular proteins that catalyse metabolic reactions. Describe the features shown by globular proteins.
Enzymes may be used to strip cell walls from plant and fungal cells. The cells are left in a solution containing a mixture of enzymes. Suggest why a different enzyme mixture is needed to remove plant cell walls compared with fungal cell walls.
Explain why maintaining an optimum pH is important when plant cells are incubated with enzymes to remove their cell walls.
A student investigated osmosis using red blood cells. The red blood cells were placed in sodium chloride (salt) solutions of five different concentrations. For each concentration, a sample was added at once to a microscope slide and the cells were observed with a light microscope for a period of time. The observations are listed in Table 3.1. Explain, in terms of water potential and osmosis, the results obtained by the student.
The student also carried out a similar investigation using plant cells with the cell walls removed. These cells were suspended in a $12\%$ mannitol solution so that the water potential inside and outside the cells was equal. Fig. 3.1 shows a photomicrograph of these cells. A sample of these cells was removed and transferred to distilled water, then viewed with a light microscope. Describe what would be expected and explain why this would not occur in normal plant cells.