BI-618
Digestive enzymes
Biology · Secondary 3 · Hard · Digestive enzymes
Four test‑tubes each contain 2 cm³ of starch suspension. They are treated as follows before adding amylase and leaving for 20 minutes.
- Tube 1: 37 °C, pH 7
- Tube 2: 10 °C, pH 7
- Tube 3: 37 °C, pH 3
- Tube 4: 90 °C, pH 7
After 20 minutes, iodine solution is added to each tube. In which tube will the mixture remain blue‑black?
- Tube 1: 37 °C, pH 7
- Tube 2: 10 °C, pH 7
- Tube 3: 37 °C, pH 3
- Tube 4: 90 °C, pH 7
After 20 minutes, iodine solution is added to each tube. In which tube will the mixture remain blue‑black?
- Tube 1 only
- Tubes 2 and 3 only
- Tubes 2, 3 and 4 only
- Tubes 1, 2 and 4 only
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