Use the scale bar to work out the magnification of the image in Fig. 2.1. State the formula you are using and show your working. The scale bar represents $10\,\mu\text{m}$.
State the name of structure X and give one function of it.
Name two structures visible in the cell in Fig. 2.1 that contain DNA.
Identify the structures marked A and B in Fig. 2.2.
Describe the part played by DNA in the production of systemin.
Systemin causes plant cells to make enzyme inhibitors called serpins. One of these serpins is a competitive inhibitor of some protease enzymes. It inhibits the protease enzymes found in herbivores, but it does not inhibit the proteases in plants. Suggest how this serpin inhibits only the protease enzymes in herbivores but not those in plants.
Competitive inhibitors, such as serpins, cause the Michaelis-Menten constant ($K_m$) of the enzymes they inhibit to increase. Explain why the $K_m$ value increases.