It breaks down the molecules that are too large to cross cell membranes to be absorbed
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How are the large molecules broken down?
Hydrolysis reactions (adding a molecule of water)
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What do carbohydrates break down into?
Disaccharides, then to even smaller monosaccharides
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What do lipids break down into?
Fatty acids and monoglycerides
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What do proteins break down into?
Amino acids
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What are digestive enzymes?
Digestive enzymes are enzymes that are used to break down the large molecules
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How does amylase work?
Amylase catalyses the breakdown of starch - it breaks the glycosidic bonds in starch to produce maltose
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Where is amylase produced
In the salivary glands and pancreas
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How do membrane-bound disaccharidases work?
They are enzymes attached to the cell membrane of epithelial cells lining the ileum
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What is the role of membrane-bound disaccharidases?
They break down disaccharides into monosaccharides
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What is sucrose broken down into?
Glucose and fructose, broken down by sucrase
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What is maltose broken down into?
Glucose and glucose, broken down by maltase
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What is lactose broken down into?
Glucose and galactose, broken down by lactase
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What are the bonds broken in lipids
Ester bonds
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Where are lipases produced?
The pancreas
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What is the role of bile salts?
They emulsify lipids (form the lipids into small droplets)
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Where are bile salts produced?
The liver
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Why are bile salts important?
Several small lipid droplets have a larger surface area than a single droplet - this means there is a larger area for lipases to work on
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What are micelles?
Once the lipid has been broken down, the monoglycerides and fatty acids join to the bile salts to form micelles
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What are micelles important?
They help the products of lipid digestion to be absorbed
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What are endopeptidases?
They hydrolyses peptide bonds within a protein
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What are exopeptidases?
They hydrolyses peptide bonds at the ends of protein molecules
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What are dipeptidases?
They are exopeptidases that work specifically on dipeptides
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How is glucose absorbed?
Active transport with sodium ions via co-transporter proteins
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How is galactose absorbed?
Active transport with sodium ions via co-transporter proteins
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How is fructose absorbed?
Facillitated diffusion
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How are monoglycerides and fatty acids absorbed?
Micelles move them towards the epithelium - they constantly break and reform, releasing the f.a's and m's
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How are amino acids absorbed?
Sodium ions are transported out of the epithelial cells into the ileum - they then diffuse back into the cells via sodium-dependant transporter proteins. carrying the amino acids with them
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