B2 4.3c – Student worksheet
Investigating digestion
1
A person eats a slice of buttered toast and honey. Explain why it is necessary to digest the
starch in the bread but not the simple sugar in the honey. (2 marks)
2
The liver produces bile, which plays an
important part in the breakdown of fats. To
show this, a small amount of bile was added to
some fat droplets. At the start the mixture was
examined under a microscope and then reexamined again after 20 minutes. The
appearance of each mixture is shown opposite
at ×200 magnification.
a
Measure the diameter in millimeters of the fat droplet labelled F on the diagram. (1 mark)
b
Calculate the actual diameter of this fat droplet. Show your working. (1 mark)
c
What effect does the bile have on the fat droplets? How does this help the digestion and
absorption of fat? (2 marks)
A student was investigating the action of pepsin.
He took four test pieces of capillary tubing
containing uncooked egg white. He placed the
tubes in a beaker of water and boiled the water
for 5 minutes. He then set up the apparatus as
shown in the diagram.
3
The student measured the length of the egg white
in each capillary tube at the start of the
investigation and again after 1 hour. His results are shown in the table.
a
Write a conclusion for the investigation. (4 marks)
b
Explain the changes in tubes A and B. (3 marks)
c
Explain the purpose of tube C. (1 mark)
d
Why was the temperature kept constant? (1 mark)
e
What type of food molecule does pepsin act on? (1 mark)
Tube
A
B
C
D
Length in mm
Start Finish
42
15
40
32
41
33
40
40
Sheet 1 of 1
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