EnzymesIB MYP Biology: Flashcards

Exam questions on Enzymes

1. A patient in Dubai whose pancreas is damaged cannot make enough of its digestive enzymes. Her doctor prescribes capsules containing the enzyme lipase to be taken with every meal.
   Explain why lipase can digest fat but cannot digest protein.2 marks
2. A student in Seoul investigates how temperature affects the activity of the enzyme amylase. She mixes 5 cm³ of starch solution with 2 cm³ of amylase solution in a test tube kept in a water bath. Every 30 seconds she puts a drop of the mixture into iodine solution on a spotting tile and records the time at which the iodine stops turning blue-black. She repeats this at 20 °C, 30 °C, 40 °C, 50 °C and 60 °C. The times taken were 240 s, 120 s, 60 s and 90 s for the first four temperatures. At 60 °C the iodine was still turning blue-black after 600 s.
   Describe the trend in the results between 20 °C and 40 °C.2 marks
3. The enzyme pepsin, a protease made in the human stomach, works best at about pH 2. Another protease made by the pancreas works in the small intestine, where the pH is about 8.
   Explain why pepsin would not digest protein well if it were carried into the small intestine.3 marks