ENZYME REVISION (individual)

The graph shows the activity of three digestive enzymes at differing pH levels.

Which statement is correct?

• Enzymes X and Y are both active at pH 7.

• Enzymes X and Z are both active at pH 4.

• Enzymes Y and Z are both active at pH 4.

• Enzymes Y and Z are both active at pH 8.

Which graph shows the effect of pH on the activity of a human digestive enzyme?

• A

• B

• C

• D

The graph shows the effect of temperature on the action of an enzyme.

Why does the rate of reaction change when the temperature is increased from 20 °C to 30 °C?

• more kinetic energy of particles, so more frequent collisions.

• more kinetic energy of molecules, so enzyme changes shape.

• less kinetic energy of molecules, so less collisions.

• less kinetic energy of particles, so enzyme changes shape.

Which statement explains the change in activity between X and Y?

• There are more effective collisions.

• There is a change in the enzyme shape.

• There is more substrate present.

• The kinetic energy of the molecules has increased.

Which graph shows the effect of temperature on the activity of an enzyme?

• A

• B

• C

• D

Which statement describes the effect of temperature on enzymes?

• High temperatures denature enzymes making it easy for substrate molecules to fit into the active site.

• High temperatures denature enzymes making it difficult for substrate molecules to fit into the active site.

• Low temperatures denature enzymes making it difficult for substrate molecules to fit into the active site.

• Low temperatures denature enzymes making it easy for substrate molecules to fit into the active site.

Why does low temperature decrease enzyme activity?

• It changes the shape of the active site.

• It changes the shape of the substrate and product molecules.

• It decreases the force of collisions between substrate and enzyme molecules.

• It increases the kinetic energy of the substrate molecules.

Four test-tubes were set up as shown in the table.

In which test-tube would starch be broken down the fastest?

• A

• B

• C

• D

Which statement about enzymes is correct? (choose 2 answers)

• Enzymes can build up large molecules.

• Lowering the pH always slows down the reaction rate.

• Raising the temperature always increases the reaction rate.

• The specificity of an enzyme depends on the shape of its active site.

Which is NOT the advantage of using pectinase in apple juice production?

• clearer juice appearance

• adding natural sweetness

• less production cost

• higher yield