Balanced Diet: Suitable amounts of all nutrients (carbohydrates, proteins, lipids, mineral salts, vitamins, fibre and water) required for normal healthy living.
Autotrophic Feeding: Way of feeding; food is made by the plants themselves.
Heterotrophic Feeding: Way of feeding; animals feed on ready-made food.
Digestion: Large insoluble molecules of food are broken down into small molecules
Egestion: Food that can’t be digested or absorbed is removed from the body.
Ingestion: Food is taken into the alimentary canal (digestive system).
Absorption: The small molecules are absorbed into the blood.
Mechanical Digestion: Food is broken by the teeth and churning movements of the alimentary canal.
Chemical Digestion: After the food has been chewed, the large molecules in it are broken down into small soluble molecules. Enzymes are involved in all this.
Saliva: Produced by the mouth and contains water, mucus and salivary amylase.
Mucus: It and water lubricate food so that is swallowed easily. It also lines the stomach and protects it from the acid.
Salivary Amylase: Enzyme that breaks down starch to maltose. It is found in the saliva.
Peristalsis: The contraction of the circular and longitudinal muscles in the oesophagus. It moves the food down the oesophagus.
Cardiac Sphincter: Opens to allow food into the stomach.
Gastric Glands: Mixes the food in the stomach and make gastric juice:

  • Hydrochloric Acid:
    – Kills bacteria.
    – Provides the right pH (2) for pepsin to work in.
    – Activates pepsinogen.
  • Pepsinogen:
    – Inactive form of the enzyme pepsin.
    – Works on breaking down protein into polypeptides

Bile: Fluid that flows into the duodenum (first part of the small intestine) neutralizes the acid from the stomach and makes it alkaline and it emulsifies fats (form small droplets) to help lipases work.
Pancreatic Duct: Tube that leads from pancreas to duodenum. Pancreas juice is a fluid made by the pancreas and it flows down this tube. This fluid has sodium bicarbonate to neutralize the acid.

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