Transcript The Model Gut - Inverness Royal Academy

The Model Gut
Practical 1
Mammalian Nutrition
 Learning objectives:
 By the end of the lesson you should be able to:
 State the need for digestion.
 Describe the movement of molecules across
the small intestine to the blood using your
experience of a model gut.
Introduction
 The process of ___________
absorption can be demonstrated with a
model gut.
large molecule
small
 Starch is a _________________
made up of many _______
___________
_____ joined together
glucose molecules
 ______________turns
_____
is present.
Iodine solution
black when __________
starch
 ___________
turns _________
when _______
Clinistix
purple
glucose is present
solution turns _________
orange
glucose
 Benedict’s
_______________
when ____________
is present
Visking Tubing
 Represents the
__________
“gut wall”
Glucose/ starch
mixture
Water
“food”
 Represents __________
____________
“molecules” in the gut
 Represents the blood
Aim
 To show the effect of the size of molecule on absorption
Method
1.
2.
3.
4.
5.
6.
Tie a knot at one end of a soaked piece of visking tubing and use
a dropper to half fill with the glucose/starch mixture
Seal the bag by tying a knot in the other end of the visking
tubing and rinse the bag under the tap.
Place the bag in a boiling tube and cover with water.
Remove a few drops of water from the tube and place onto a
dimple tray.
Test for sugar using a clinistix. Test for starch using iodine.
Leave for 30 minutes and then retest the surrounding water for
glucose and starch. Record your results.
Results
Glucose
At start of
experiment
At end of
experiment
X
Starch
X
X
Interpretation
 Why are only glucose molecules found in the “blood” at the
end of the experiment?
 They are very small and pass through the “gut wall”
 What must happen to starch molecules before they can be
absorbed into the “blood”
 They must be broken down into small molecules
Conclusion
 Which size of molecule is absorbed from the “gut” into the
“blood”
 Only the small molecules
Evaluation
 Why is the visking tubing bag washed before being placed in
the boiling tube?
 Any glucose or starch on the outside of the bag will give false
positive results