The digestion process

• Food is broken down in the alimentary system from large pieces/molecules into smaller molecules.
• The food most mammals ingest is in large pieces e.g. leaves, grass, cake, meat etc.
• All mammals have teeth to bite off the food and chew it.
• Food is broken down into smaller molecules by the chewing acting of teeth.
• Mechanical digestion this is when food is broken down by the chewing action of teeth.
• This is physical change.
• The strong muscular walls of the oesophagus and the stomach also help in breaking down food into smaller pieces.
• Juices from the salivary glands and the stomach are also mixed with the food.
• Insert peristalsis diagram here.
• Peristalsis- the action by which muscles push the food down along the alimentary canal.
• The muscular walls around the food contract to squeeze the food along the tube.
• The muscles in front of the food relax.
• As food passes along the tube the small pieces of food are also chemically changed.7
• Large molecules are converted into smaller ones.
• This process is carried out by enzymes.
• Enzyme-is a special molecule that speeds up a chemical reaction.
• They are biological catalysts.
• Enzymes are found in all living cells and in digestive juices such as saliva.
• The enzyme molecules become attached to the food molecules and split them into smaller ones.
• Enzymes can act on food more easily if it is in smaller pieces.
• This results in a larger surface area for them to act on.
• This is achieved by chewing which results in food pieces becoming smaller and presenting a larger surface area.

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