Learning focus
Build precise biological explanations, interpret diagrams and data, and connect structure, process and practical evidence.
Ingestion and chewing
Ingestion is taking food into the mouth. Teeth physically digest the food, while the tongue mixes it with saliva and forms a bolus for swallowing. Chewing increases surface area and makes the bolus easier to move through the oesophagus.
Saliva
Saliva moistens food, dissolves some chemicals for taste and contains mucus that lubricates the bolus. It also contains amylase. Salivary glands release saliva into the mouth through ducts.
Amylase action
Amylase catalyses the breakdown of starch to maltose. The reaction begins in the mouth under near-neutral conditions. It may continue briefly in the bolus after swallowing, but stomach acid eventually inactivates or denatures salivary amylase.
Testing the reaction
Starch disappearance can be followed by placing samples onto iodine at timed intervals. A blue-black result means starch remains; yellow-brown means it is no longer detected. The endpoint is not proof that glucose has formed because amylase produces maltose.
Experimental control
To investigate one factor, keep enzyme and starch concentrations, volumes, temperature, pH and sampling intervals controlled. Separate droppers prevent iodine or enzyme contamination. Repeats and means improve reliability.
Practical or data skill
Investigate amylase at one controlled temperature. Mix starch and amylase, sample at fixed intervals and record the time when iodine no longer turns blue-black. Use eye protection and a spotting tile.
Examination tip
Amylase produces maltose, not glucose. Maltase later converts maltose to glucose.
Review questions and suggested answers
Question 1
What is the substrate of amylase?
Suggested answer
Starch.
Question 2
What is the product of amylase action?
Suggested answer
Maltose.
Question 3
Why is food chewed before swallowing?
Suggested answer
To make smaller pieces, increase surface area and form a manageable bolus.
