Enzyme

Question 1

Enzyme

Answer 1

• Enzymes are proteins that act as biological catalysts - this means they speed up reactions without being used up.
• An enzyme works on the substrate, forming products.
• An enzyme’s active site and its substrate are complementary in shape.

Question 2

Factors affecting enzyme activity

Answer 2

As temperature increases to the optimum, the kinetic energy of the enzyme and substrate increases, causing more collisions between the enzyme and substrate complexes leading to an increase in enzyme activity.
An increase in temperature beyond the optimum causes the enzyme’s active site to become denatured.

Question 3

pH

Answer 3

Deviating from the optimum pH (too high or too low) causes the enzyme’s active site to become denatured and the active site loses its important shape. It can no longer form enzyme-substrate complexes, leading to a decrease in enzyme activity.

Question 4

Concentration of the enzyme

Answer 4

The higher the enzyme concentration, the more enzymes there are to form enzyme-substrate complexes, leading to an increase in enzyme activity. This happens up to a certain point. Enzyme activity then levels off (plateaus) as there are not enough substrate molecules to react with the extra enzymes.

Question 5

Effect of Temperature on the action of an enzyme (Method)

Answer 5

• First place single drops of iodine solution in rows on the dimple tiles.
• Label the test tubes with the temperature to be tested
• Use the syringe to place 2 cm cubed of amylase into the test tube.
• Place the test tube into a water bath.
• Use another syringe to add 2 cm cubed of starch to the amylase solution. Then start the stop clock and leave it on throughout the test. Mix using a pipette.
• After 10 seconds, use the plastic pipette to place one drop of the mixture on the first drop of iodine. The iodine solution should turn - black.
• Squirt the rest of the solution in the pipette back into the test tube.
• Wait ten seconds, then remove a second of the drop of the mixture to add the next drop of iodine.
• Repeat the previous step until the iodine solution and the amylase starch remain orange.