Digestive System

Topics: Digestion, Protein, Enzyme Pages: 3 (973 words) Published: May 18, 2011
Biology Summer Task

Our digestive systems contain glands. These glands produce enzymes. Enzymes are catalysts. Catalysts make chemical reactions happen quicker and easier. Digestive enzymes help us to break down food easier. Our bodies make lots of different digestive enzymes. Each enzyme breaks down a particular food. When an enzyme has broken down one food molecule, it can then break down another molecule of the same kind. It can do this over and over again. It makes the reaction happen without being used up.

In the digestive system, enzymes are produced to break down carbohydrates, proteins and fats into smaller soluble molecules from large food molecules. These spread through the tube of the small intestine and into the blood plasma (carbohydrates and proteins) or lymph (fats) and pass to the cells. The stomach makes hydrochloric acid to help the enzyme called pepsin work. Fats are difficult to digest and absorb because they are not soluble in water. To help with fat digestion the gall bladder produces bile this makes the fats smaller. This increases their surface area for enzymes to act on. In the mouth is saliva and they containing amylase produced by the salivary glands. This enzyme is used to break down starch/carbohydrates into glucose molecules. In the stomach is found Pepsin which breaks down proteins into amino acids. In the small intestine, parts of a large molecule of fat are broken down into smaller fatty acid and glycerol molecules.

Below is how the different foods are digested by using enzymes:

1. Carbohydrates - Foods rich in carbohydrates include bread, potatoes, dried peas and beans, rice, pasta, fruits, and vegetables. Many of these foods contain both starch and fibre. The digestible carbohydrates such as starch and sugar are broken into simpler molecules by enzymes in the saliva, in juice produced by the pancreas, and in the lining of the small intestine. Starch is digested in two steps. First, an enzyme in the saliva and...
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