Transcript Accessory Organs and Enzymes

Accessory Organs
and Enzymes
Unit D – Human Systems
Accessory Organ
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An organ that assists with the functioning of
some other organ within a system.
For example, the gallbladder, liver and
pancreas are not part of the gastrointestinal
tract, but they play key roles in aiding
digestion.
Digestion Review Video
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The liver, pancreas and gallbladder all
secrete (or release) fluids from their cells.
These fluids contain enzymes that break
down large organic molecules (carbs,
proteins, lipids) into smaller molecules that
can be absorbed into the bloodstream to be
transported to cells of the body.
Salivary Glands
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Secrete amylase enzyme.
Amylase breaks down starches or
polysaccharides into shorter chains of
sugars.
Stomach
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Secretes pepsinogen enzyme.
Pepsinogen is the inactive form of the
enzyme. It is “switched on” by the presence
of hydrochloric acid and converted into
pepsin.
Pepsin takes proteins and breaks them into
longer chains of amino acids called
polypeptides.
Liver
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Continuously produces a fluid called bile,
which is concentrated and stored in the
gallbladder.
When the presence of fats is detected in
the small intestine, a hormone called is
released and signals the gall bladder to
release bile salts.
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Bile salts travel to the small intestine where
they emulsify or break down large fat
globules.
The fat globules can then be exposed to
enzymes which can break the fats down.
Other Functions of Liver
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Storage of vitamins and of excess glucose
in the form of glycogen.
Detoxifies potentially harmful compounds
like alcohol.
Breaks down and removes nitrogen from
amino acids, forming urea, the major
component of urine.
Pancreas
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When acidic fluids from the stomach reach
the small intestine, a hormone called
secretin enters the bloodstream and
signals the pancreas to release bicarbonate
(HCO3-) ions.
Bicarbonate ions are basic or alkaline and
neutralize the acidic stomach fluids.
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The enzymes enterokinase, trypsinogen,
erepsin, amylase, and lipase are also
secreted from the pancreas when food from
the stomach enters the small intestine.
Enterokinase enzyme activates
trypsinogen into its active form, trypsin.
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Trypsin takes long chain polypeptides and
breaks the chemical bonds between them,
and converts them into shorter chain
polypeptides.
Erepsin enzymes take short chain
polypeptides, dissolve the chemical bonds
and release individual amino acids.
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Starches that have not been broken down
can be digested in the small intestine by
pancreatic amylase into shorter chains of
sugars called disaccharides.
Fats are broken down by enzymes called
lipases into glycerol and fatty acids.
Small Intestine
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As well as being the major site of chemical
digestion, also releases enzymes.
Disaccharidases break down
disaccharides into monosaccharides. The
three major disaccharidases are maltase,
lactase and sucrase.
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Once food has been broken down into
individual monosaccharides, amino acids
and fatty acids, these can be absorbed by
villi into the bloodstream and lymphatic
system.
Undigested food carries on travelling to the
large intestine.
Student Tasks for Lesson
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Complete “Enzymes of the Digestive
System” Table.
Complete pg. 263 #10, 12, pg. 266 #1-7 for
your homework book.
Major assignment to be handed in:
Complete a flow chart involving all organs
of digestion, major sites of chemical and
physical digestion and all enzyme action.