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The digestive system is made up of a long muscular tube
Enzymes and digestion
and its associated glands
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The digestive system is an exchange surface Physical Breakdown: food is broken down into smallthrough which food substances are absorbed
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This makes it possible to ingest the food but also provides a large surface area
Parts of the Digestive System:
for chemical digestion
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cles in the stomach wall that also physically break it
Stomach: a muscular sac with an inner layer that produces up
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Its role is to store and digest food, especially
Chemical Digestion: this hydrolyses large, insoluble
proteins
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Carried out by
proteins
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Ileum: a long muscular tube (small intestine) food is furEnzymes are specific so usually one enzyme hydrolysther digested in the ileum by enzymes that are produced
es a large molecule into sections and then these are
by its walls and by glands that pour their secretions into it
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surface area
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villus
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Lipases: hydrolyse lipids into glycerol and fatty acids
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Most of this is from the
secretions of the many digestive glands
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The faeces are stored
here before periodically being removed via the anus
through egestion
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These contain the enzyme amylase = hydrolyses
starch into maltose
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This contains proteases to hydrolyse proteins, lipase to hydrolyse lipids and amylase to hydrolyse
starch
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Usually takes more than one enzyme to completely
hydrolyse a large molecule
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This hydrolyses
the alternate glycosidic bonds of the starch molecule
to produce the disaccharide maltose
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The process:
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Saliva enters the mouth from salivary glands and
is thoroughly mixed with the food
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Food is swallowed and enters the stomach where
the conditions are acidic
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After a time the food passes into the small intestine = mixes with secretion from the pancreas
(pancreatic juice)
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Muscles in the intestine wall push food along the
ileum
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Its apart of the cell-surface membranes of the epithelial cells that line the ileum
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Protein Digestion:

Proteins are large, complex molecules that are
hydrolysed by a group of enzymes called peptidases (proteases) there are different types:
Sucrase: hydrolyses the single glycosidic bond in the
sucrose molecules = produces glucose and fructose
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= produces glucose and galactose
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Exopeptidases: hydrolyse the peptide bonds on
the terminal amino acids of the peptide molecules formed by endopeptidases
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Lipid Digestion:
Lipids are hydrolysed by enzymes called lipases = enzymes produced in the pancreas that hydrolyse the
ester bond found in triglycerides to form fatty acids
and monoglycerides
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Lipids (fats and oils) are firstly split up into tiny droplets
called micelles by bile salts which are produced by the
liver
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Dipeptidases: hydrolyse the bond between the
two amino acids of a dipeptide
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Lactose Intolerance:
As milk forms a less significant part of an adults diet,
the production of lactase diminishes as children get
older
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If you produce no lactase you cannot hydrolyse the
lactose you consume
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This produces a large volume of gas that can result in
diarrhoea because the soluble molecules lower the water potential of the material in the colon

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