(a) Make a labelled diagram of the vertical section of the mammalian tooth. (b) Describe the role of the following in mammalian nutrition: (i) teeth; (ii) t...

(a) Labelled diagram of a vertical section of a mammalian tooth

(b) Roles in mammalian nutrition

1. Teeth: They cut, bite, tear and grind food during mastication. This breaks food into small particles, increases its surface area for enzyme action and makes swallowing easier.
2. Tongue: It moves food around the mouth during chewing, mixes it with saliva, moulds the food into a bolus and pushes the bolus into the pharynx for swallowing. It also bears taste buds for tasting food.
3. Saliva: It moistens and lubricates food, making chewing and swallowing easy. It acts as a solvent for soluble food substances and contains salivary amylase (ptyalin), which begins the digestion of cooked starch to maltose. It is slightly alkaline.
4. Stomach: It temporarily stores food and churns it, thereby mixing it with gastric juice. Gastric juice contains hydrochloric acid, which provides an acidic medium and kills many bacteria, and pepsin, which starts protein digestion. In young mammals, rennin coagulates milk protein.

(c) Test for protein: Biuret test

1. Prepare an aqueous suspension or solution of the food sample in a clean test tube.
2. Add about 2 cm³ of dilute sodium hydroxide solution and shake.
3. Add a few drops of dilute copper(II) sulphate solution and mix gently.

Observation: A violet or purple colour indicates the presence of protein. If protein is absent, the mixture remains blue.