3.4 Summary Questions & Exam Style Questions

Question 1

Describe the features of enzymes essential to their role as components in biosensors. [3]

Answer 1

(enzymes have) active site (1); (active site) specific (1); to, substance / molecule, testing for (1)

Question 2

Why does Benedict’s reagent turn red when warmed with a reducing sugar? [2]

Answer 2

Reducing sugars react with copper ions in Benedict’s reagent resulting in the addition of electrons to
blue Cu2+ ions (1), reducing them to Cu+ ions which form a brick red precipitate (1).

Question 3

Explain why an iodine test is used in experiments to show that plants require light for photosynthesis. [3]

Answer 3

In an iodine test a purple/black colour indicates the presence of starch (1). Starch is a product of
photosynthesis (1). The test shows that starch is produce when light is available to the plant, but not
when the plant is kept in the dark (1).

Question 4

Suggest how reagent strips might be useful in the management of the medical condition diabetes, where a person’s blood sugar level can become too high. [4]

Answer 4

Reagent strips are quantitative (1); they can be used to estimate the concentration (1) of reducing
sugar (glucose) (1) in the blood. They are simple to use and interpret (1).