Catalase is an enzyme that is found in many plant cells and animal cells. Catalase breaks down hydrogen peroxide, which is a waste product from cell metabolism. Fig. 1.1 shows the breakdown of hydrogen peroxide by catalase. 2 H₂O₂ hydrogen peroxide catalase 2 H₂O water + O₂ oxygen Fig. 1.1 A student decided to investigate how catalase activity varies along the length of a carrot root. Fig. 1.2 shows a photograph of some carrots. [Figure 1.2] leaves shoot carrot root Fig. 1.2 The student extracted catalase from different parts of the carrot root tissue. • Carrot root tissue was mixed with a small volume of pH7 buffer and some fine sand. • The mixture was ground with a pestle and mortar. • The mixture was placed into a centrifuge tube and spun in a variable speed centrifuge for a few minutes. • This caused the mixture to be separated into a solid pellet at the bottom of the centrifuge tube and a liquid carrot extract at the top, as shown in Fig. 1.3. • The liquid carrot extract was poured into a clean test-tube. This liquid contained catalase. Fig. 1.3 shows a centrifuge and centrifuge tube with its contents, after spinning in the centrifuge for a few minutes. [Figure 1.3] lid of centrifuge tube plastic centrifuge tube (2.0 cm³) liquid carrot extract solid pellet Fig. 1.3