A student mixes starch with saliva containing the enzyme amylase. After a while, all of the starch has been broken down into sugars.
Which statement describes the amylase after the reaction?
It can catalyse another sample of starch because it has not been used up.
It must be re-formed before it can catalyse another sample of starch.
It has been used up, so more amylase must be added to break down more starch.
It will continue to make more sugar after all of the starch has reacted.
122 exam-style questions on OCR GCSE Chemistry 5.2 Controlling reactions, covering 5.2.1 Measuring and interpreting rate of reaction, 5.2.2 Factors affecting rate and collision theory, and 5.2.3 Catalysts, activation energy and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.