Biology Questions and Answers
secretions only the bile does not contain
digestive enzymes.
- Why do protease-
supplying cells of the stomach
and of the pancreas make only
precursors of the active
proteolytic enzymes?
The stomachzymogens of the proteases pe and the pancreaspsin, make
chymotryzymogens are psin anreleased d trypsin ainto thnd thesee gastric (^)
or duodenal lumen for activation. This
happens to these organs' (stomach anprevent the digestion od pancreas)f (^)
own cells and tissues by the active form
of the enzymes. So the production ofzymogens is a protective strategy
against the natural efproteolytic enzymes.fects of the
- After digestion the next
step is absorption done by
cells of the mucous membrane
of the intestine. For this task a
large absorption surface is an
advantage. How is it possible
in the small internal space of
the body of a pluricellular
organism to present a large
intestinal surface?
Evolution tried to solve this problem in
two ways. Ttubular shape of the bowelshe simplest is the long and
(approximately eight meters in
extension), numerous small intestine making possible loops foldthat (^)
closely. More efficient solutions are the
intestinal villi and the microvilli of the
mucosal membrane cells.
The intestinal wall is not smooth. The
mucous memsubmucosa, pbrane, together with itsrojects inside the gut
lumen like glove fingers forming
invaginations anavailable surface d villi that multiply thfor absorption. In e
addition the epithelial cells that cover
these villi havhairlike projections called e themselves numicrovillimerous on (^)
the external face (lumen face) of their
plasma membrane. The absorptive arof the intestines is thus increased ea
hundreds of times with these solutions.
In the jejunum and ileum there are
folds that havincreasing the absorption e the function osurface f (^) too.
- In which part of the
digestive tube is water is
chiefly absorbed? What about
the mineral ions and vitamins?
Most part of water, vitamins anmineral ions are absorbed by the smalld (^)
intestine. The large intestine, however,
is responsiblnearly 10% oe for the reabsorf the ingested water, ption oanf (^)
important amount that gives
consistencycause diarrhea). to feces (colon diseases can
- From the intestinal lumen
through to the tissues - what
is the route of nutrients after
digestion?
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