The diagram shows a student's mouth while she is eating a cracker. Saliva mixes with the food and starts chemical digestion. The student notices that a crac...
Question 1 Report
The diagram shows a student's mouth while she is eating a cracker. Saliva mixes with the food and starts chemical digestion. The student notices that a cracker tastes sweeter after it has been held in the mouth for about a minute. The teacher asks the class to use the diagram to link structures in the mouth with this observation.
(a) Name the structures labelled P and Q. [2]
(b) Describe the mechanical action of teeth on the cracker. [2]
(c) Explain why the cracker may taste sweeter after one minute in the mouth. [3]
(d) State one way that saliva helps food move through the digestive system. [2]
Answer Details
(a) P is a salivary gland and Q is the tongue. [2 marks]
(b) Teeth carry out mechanical digestion: they cut, tear or grind the cracker into smaller pieces. [2 marks] This increases the food surface exposed to digestive enzymes.
(c) Saliva contains the enzyme amylase. Amylase digests starch in the cracker, producing maltose or other sugars, which taste sweet. [3 marks]
(d) Saliva moistens and lubricates food, making it easier to swallow and move through the digestive system. [2 marks]
Examination reminder: Mechanical digestion makes pieces smaller but does not make new substances. Chemical digestion by amylase changes starch into sugar.
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