Enzymes in synthesis and digestion, and rate calculations

Overview

Calculating rate as 1 divided by time and as volume per unit time, comparing rates, carbohydrases, proteases and lipases and their products, enzymes building carbohydrates, proteins and lipids, and giving calculated answers to an appropriate number of significant figures.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   How is the rate of an enzyme-controlled reaction calculated from the time taken for a reaction to finish?

   Model answer

   Divide 1 by the time taken. The rate is then expressed per second, written s⁻¹.

2. 2

   Starch is fully broken down in 40 seconds. Calculate the rate of reaction.

   Model answer

   The rate is 0.025 per second, because 1 divided by 40 gives 0.025.

3. 3

   An enzyme releases 24 cm³ of oxygen in 30 seconds. Calculate the mean rate of oxygen production.

   Model answer

   The mean rate is 0.8 cm³ per second, because 24 divided by 30 gives 0.8.

4. 4

   A reaction produces 15 cm³ of gas in 5 minutes. Calculate the rate in cm³ per minute.

   Model answer

   The rate is 3 cm³ per minute, because 15 divided by 5 gives 3.

5. 5

   Reaction A finishes in 20 seconds and reaction B in 80 seconds. How many times faster is reaction A?

   Model answer

   Reaction A is 4 times faster, because 80 divided by 20 gives 4.

6. 6

   Explain why a rate calculated as 1 divided by time is useful when comparing enzyme experiments.

   Model answer

   It converts times into a measure that increases as the reaction gets faster, so results can be compared directly across different conditions.

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