The effect of temperature on the rate of decomposition by an enzyme: data analysis and evaluation | Exit Quiz | Oak Nati

In an experiment to determine the effect of temperature on the rate of decomposition by an enzyme, it takes 5 seconds for the indicator to reach the end point. What is the rate of the reaction?

• 5

• 1

• 0.5

• 0.2

• 0.02

Answer explanation

The correct answer is 1/5 = 0.2

A range of equipment and chemicals are used in the experiment to determine the effect of temperature on the rate of decomposition by an enzyme. Match the words with their function in the experiment.

• fatty acids

• indicator (used to measure the end point)

• lipids

• found in milk (the substrate)

• Cresol red

• the product (decreases pH of the solution)

• lipase

• enzyme (works on lipids)

Answer explanation

Lipase is the enzyme used. This breaks down the lipid (the substrate) in the milk. The lipids are broken down into the products (fatty acids). As the fatty acids increase the solution becomes more acidic. The indicator changes colour (the end point).

At which of the following points are enzymes being denatured?

• a

• b

• c

Answer explanation

The correct answer is 'c'. As the temperature increases, the rate of reaction slows. This is because the enzyme's (a protein) shape is changed as the temperature breaks bonds. This changes the active site shape so the substrate no longer fits.

Point b in the graph is known as the enzyme's optimum temperature. Which of the following statements explains what is happening at point 'b'?

• The active sites of the enzymes are changing as it becomes denatured.

• The number of collisions between enzymes & substrate are most frequent.

• There are fewer collisions taking place between the enzyme and substrate.

Answer explanation

At point b, all of the enzyme's active sites are full of substrate because there are very frequent collisions taking place. The enzyme is working as fast as it can. The temperature where this happens is known as the optimum temperature.

What is the name of the part of the enzyme that the substrate needs to collide with for a reaction to take place?

How does keeping food such as meat or fish in the fridge help to slow the rate of decomposition?

• The fridge door prevents oxygen from getting into the fridge.

• The low temperature of the fridge slows enzyme activity.

• The fridge helps to dry the food.

• The low temperature increases the number of bacteria

Answer explanation

A fridge helps to slow the rate of decomposition by reducing the temperature. At lower temperatures, fewer collisions take place between the enzymes and the substrate and so the rate of reaction is slowed down.