The fig tree, Ficus carica, and the papaya tree, Carica papaya, produce a milky-looking fluid known as latex. The latex is released when plant tissue is wounded and it is thought to act as a defence against attack by herbivorous insects or parasitic worms. Latex is a complex mixture of substances and the exact composition of the mixture depends on the plant species. A group of enzymes that hydrolyse proteins, known as cysteine proteases, are commonly found in latex. Ficin, found in F. carica, and papain, found in C. papaya, are both cysteine protease enzymes. These enzymes have been extracted and purified for use commercially. (a) An investigation was carried out to compare the effect of temperature on the activity of ficin and papain. The results are shown in Fig. 5.1. [Figure 5.1]

1. (a)(i)With reference to Fig. 5.1, describe the differences between the activity of papain compared to the activity of ficin between 20 °C and 80 °C.[3]
2. (a)(ii)Ficin and papain have been shown to be effective in the digestion of parasitic nematodes (roundworms). With reference to Fig. 5.1, explain which enzyme you would select to use in an oral medication for the treatment of human intestinal parasitic nematodes.[1]
3. (b)One commercial use of the enzyme ficin is the production of Fab fragments (antigen binding regions) of mouse IgG antibodies for use in immunological studies. The process uses immobilised ficin to cleave (cut) the antibodies in the hinge region. Suggest one practical advantage of using immobilised ficin for this process, rather than ficin free in solution.[1]
4. (c)(i)Streptopain is secreted to the outside of the cell. State the term given to an enzyme that is produced by a cell and is then secreted to the outside, where it has its action.[1]
5. (c)(ii)Suggest one example of a structural protein in connective tissue that can be hydrolysed by streptopain.[1]

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