Teaching enzymes to pre-service science teachers through POE (predict, observe, explain) method: The case of catalase

Annex 1: The Effect of Catalase
The effect of catalase on H₂O₂ was focused on in this activity. In this regard, 2 ml H₂O₂ was added into a clean test tube. The calf lifer that had been brought beforehand was divided into small and equal pieces. Then one of these pieces was put in the prepared test tube (Figure 1).

2 ml H₂0₂
Liver piece
Figure 1. Catalase Concentration

Annex 2: Catalase Concentration
Calf liver, potato, chicken, and apple were used in this activity for determining the concentration of catalase in different living being pieces. 2 ml H₂O₂ and equal amounts of liver, potato, chicken, and apple pieces were put in each one of four test tubes (Figure 3).

Figure 3. Catalase Concentration

Annex 3: Relationship between Catalase Concentration and Surface Increases in a Liver Piece
In this activity, attention was focused on the enzymatic relationships of the liver piece slices containing catalase and their mashed use in equal volumes with equal amount of substrate. 2 ml H₂O₂ was added into each one of three test tubes. Three calf liver pieces were taken in equal amounts. One of the liver pieces was regularly sliced. The second one was minced. The third one was pounded. These liver pieces were added into the test tubes containing H₂O₂, and the reactions taking place in the tubes were observed at specific intervals (Figure 4).

Figure 4. Relationship between Catalase Concentration and Surface Increases in a Liver Piece

Annex 4: Can Catalase Be Reused?
This activity focused on the reusability of enzymes. In this regard, 2 ml H₂O₂ solution and a piece of liver were added into a clean test tube. The initial liquid was poured into the first test tube, and it was assumed that the reaction was completed. The students were asked to observe the changes occurring and the gas bubbles coming out when the liver was added to this liquid and 2 ml H₂O₂ was added onto the liver remaining in the second test tube (Figure 5).

Figure 5. Can Catalase Be Reused?