Human Digestive System

Source

• Insoluble food has to be digested before it can be absorbed
• Chewing takes place in the mouth and breaks up the food
• Digestion starts digesting starch in the mouth. Amylase starts the process
• In the small intestine the starch has changed to glucose, so the digestion has stopped
• When starch is completely digested glucose is formed
• The digestion of protein starts in the stomach with an enzyme called pepsin
• The digestion of protein finishes in the small intestine
• The protein changes to amino acids after digestion
• In the small intestine, soluble food is absorbed into the blood
• In the rectum the water is taken out of the waste and the waste pushed together. This makes faeces.

Ingestion: food is taken into the alimentary canal
Digestion: large nisoluble molecules are broken down into smaller soluble molecules
Absorption: small molecules are absorbed into the blood stream
Egestion: waste material passes out

Enzymes

• They are biological catalysts
• They speed up a reaction but remain unchanged at the end and can be used again
• Enzymes are proteins
• They are denatured (cease functioning) at high temperatures
• They are sensitive to pH
• Enzymes are apecific, only on enzyme will work with one substrate.

Carbohydrases

• Carbohydrases work on carbohydrates and break them down into simple sugars (e.g. Glucose). Amylase is an example of a carbohydrase

Proteases

• These work on proteins and break them down into amino acids. Examples include pepsin and trypsin.

Lipases

• These work on fats (lipids) and break them down into glycerol and fatty acids, for example lipase.

	Amylase	Pepsin	Trypsin	Lipase
Where produced	Salivary glands and pancreas	Walls of stomach	Pancreas	Pancreas
Where functions	Mouth	Stomach	Small Intestine	Small Intestine
What they do	Break down of starch	Break down of protein	Break down of protein	Break down of fat