Amylase is an enzyme that digests starch - AQA - GCSE Biology Combined Science - Question 3 - 2022 - Paper 1

The independent variable in this investigation was the pH of the amylase solution.

The student would know that all the starch has been digested when the iodine solution does not change color. Normally, the iodine turns blue-black in the presence of starch, and if there is no change, it indicates that starch is no longer present.

The optimum pH for the amylase, according to Figure 6, is 6.8.

It took 82 seconds for the amylase to digest all the starch, as indicated in Figure 7.

To determine the rate of sugar production at 40 seconds, a tangent can be drawn at that time on Figure 7. The rate can be calculated as follows:

Let

• $ext{dy}$ = value of sugar concentration at 40 seconds
• $ext{dx}$ = change in time (in seconds)

Using the values from the graph,

• $ext{dy} = 4 - 2 = 2$ ext{ (arbitrary units)}
• $ext{dx} = 40$ seconds

Thus, the rate is given by:

ext{Rate} = rac{ ext{dy}}{ ext{dx}} = rac{2}{40} = 0.05 ext{ (arbitrary units per second)}

Converting to per minute: $0.05 imes 60 = 3 ext{ (arbitrary units per minute)}$

Enzymes, such as amylase, are protein molecules that have a specific three-dimensional (3D) structure essential for their function. This structure contains an active site where the substrate, in this case starch, fits.

When the pH of the environment changes, it can alter the charge and shape of the enzyme's active site. If the pH deviates from the optimum level, the enzyme may become denatured, losing its functional shape, and can no longer bind effectively to the substrate.

As pH is adjusted, the shape of the active site can also change, which affects the enzyme's ability to catalyze reactions. At extreme pH values, the enzyme can unfold entirely, interfering with starch digestion. Thus, maintaining an optimal pH ensures that the amylase can efficiently digest starch.