Animal organisation - digestion - AQA

The major nutrients required for a healthy diet are carbohydrates, proteins and lipids. The digestive system breaks down large molecules of food, which are then absorbed into the bloodstream.

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Combined Science

Organisation

Digestive enzymes

The groups of enzymes involved in the breakdown of food are:

Carbohydrases break down carbohydrates:

$\mathbf{carbohydrate}\; \overset{\mathbf{carbohydrase}}{\rightarrow}\; \mathbf{simple\; sugars}$

Starch is a type of carbohydrate. The carbohydrase that breaks down starch is amylase:

$\mathbf{starch}\; \overset{\mathbf{amylase}}{\rightarrow}\; \mathbf{glucose}$

Proteases break down proteins:

$\mathbf{protein}\; \overset{\mathbf{protease}}{\rightarrow}\; \mathbf{amino\; acids}$

Lipases break down lipids:

$\mathbf{lipid}\; \overset{\mathbf{lipase}}{\rightarrow}\; \mathbf{fatty\; acids}\;\mathbf{+\; glycerol}$

Carbohydrases

Carbohydrases break down carbohydrates in several regions of the digestive system.

Most of the carbohydrate we eat is starch, so this will be the main substrate in the early part of digestion for enzyme action.

Region of digestive system	Enzyme	Where produced	Substrate	Broken down into
Mouth	Salivary amylase	Salivary glands	Starch	Maltose
Small intestine - Duodenum	Pancreatic amylase	Pancreas	Starch	Maltose
Small intestine - Ileum	Amylase	Wall of ileum	Maltose	Glucose

Proteases

Proteases break down proteins in several regions of the digestive system.

Region of digestive system	Enzyme	Where produced	Substrate	Broken down into
Stomach	Protease - pepsin	Gastric glands in stomach	Proteins	Begins the breakdown into amino acids
Small intestine - Duodenum	Protease - trypsin	Pancreas	Proteins	Continues the breakdown into amino acids
Small intestine - Ileum	Protease - peptidase	Wall of ileum	Peptides	Completes the breakdown into amino acids

Lipases

Lipases break down lipids in one region of the digestive system.

Region of digestive system	Enzyme	Where produced	Substrate	Broken down into
Small intestine - Duodenum	Lipase	Pancreas	Lipids	Fatty acids and glycerol

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