Food molecules we ingest are too big to be absorbed directly from the digestive system into the blood. They have to be physically and chemically broken down into smaller soluble molecules.

The Digestive System

Food is physically digested by chewing food in the mouth and by chemically by special chemicals called enzymes in the digestive system.

Large food molecules are broken down into smaller food molecules so that they can be absorbed into the blood at the small intestine.

Once all the useful nutrients and energy have been absorbed by the body waste is egested (removed) at the anus below the rectum.

Enzymes

Enzymes are Biological Catalysts that are produced by parts of your digestive system to help chemically digest food. Enzymes speed up the breakdown of food into smaller molecules.

They are very specific. Three main enzymes:

· Lipase - break Lipids (fats) down into Fatty Acids and Glycerol

· Protease - break Proteins down into Amino Acids

· Amylase breaks Starch down into Glucose

Starch is a Carbohydrate and Amylase is a Carbohydrase Enzyme.

All substances are made from Atoms.

Any two or more atoms joined together form a Molecule.

If the atoms are all the same it is an Element.

If there are two or more different Atoms in the Molecule it is a Compound. The Element Sodium (Na) chemically joins with Chlorine (Cl) to for Sodium Chloride (NaCl)

The new compound (Salt) is completely different to the Sodium and Chlorine Elements.

Most substances are Compounds as there are only just over 100 Elements, listed on the Periodic Table. Each element has its own symbol on the table and position.

The table has Groups from 1-0 going from top to bottom and Periods 1-7 going across.

Lithium (Li) is in Group 1

Chlorine (Cl) is in Group 7

Calcium (Ca) is in Period 4

Helium (He) is in Period 1

Chemical Symbols and Formula

Symbols and formula are used to represent atoms, element and compounds.