Activity Book

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Activity Book
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Practical 12.1 Examination of the mammalian
alimentary canal and its associated
glands Practical 12.2 Investigation of the
change in pH in the mouth before and after eating
candies Practical 12.3 Design an investigation
of the action of digestive enzymes Practical
12.4 Investigation of the effect of bile salts
on oil
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Practical 12.5 Stimulation of digestion and
absorption in the small intestine using a
dialysis tubing STS connection 12.1 Relation of
diet, eating habit and oral hygiene to tooth
decay STS connection 12.2 Fluoridated water
versus fluoride toothpaste with
calcium Activity 12.3 Fate of food in our
body Exercise 12
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12.1
Examination of the mammalian alimentary canal and
its associated glands
Questions
1 Identify structures A to L.
ANS ?
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12.1
Examination of the mammalian alimentary canal and
its associated glands
2 Which processes of nutrition are carried out by
the following structures?
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12.2
Investigation of the change in pH in the mouth
before and after eating candies
Questions
1 Account for the change in pH after eating the
candy.
The oral bacteria convert sugars in the candy to
acids. These acids lower the pH of the plaque.
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12.2
Investigation of the change in pH in the mouth
before and after eating candies
2 Explain why people who drink soft drinks
throughout the day are more likely to have tooth
decay.
Frequent drinking of soft drinks results in a
constant attack of the teeth by acids.
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12.2
Investigation of the change in pH in the mouth
before and after eating candies
3 Why does the chewing of sugar-free gum may help
prevent tooth decay?
It stimulates the secretion of saliva which can
wash off the acids from the plaque and neutralize
the acids.
ANS ?
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12.2
Investigation of the change in pH in the mouth
before and after eating candies
4 Suggest three ways to reduce the chance of
having tooth decay.
Eat fewer sugary foods. Brush the teeth after
eating to remove any food debris. Avoid frequent
snacking.
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12.2
Investigation of the change in pH in the mouth
before and after eating candies
Conclusion
What conclusion about the effect of eating
candies on the change in pH in the mouth can you
draw from this practical?
Eating candies can lead to a drop in pH in the
mouth when the sugars are converted to acids by
the oral bacteria.
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12.3
Design an investigation of the action of
digestive enzymes
Design and perform an experiment
1 At which temperature are you going to conduct
your experiment? Why?
37?C. To simulate the body temperature at which
pepsin works well.
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12.3
Design an investigation of the action of
digestive enzymes
2 What are the controlled variables in this
experiment?
Number and size of egg white cubes, temperature
and total volume of solution, etc.
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12.3
Design an investigation of the action of
digestive enzymes
3 What is the independent variable in this
experiment?
The solutions in the test tubes.
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4 What is the dependent variable in this
experiment?
The disappearence of egg white cubes.
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12.3
Design an investigation of the action of
digestive enzymes
5 What are the controls in this experiment?
A test tube with an egg white cube, hydrochloric
acid and distilled water. A test tube with an egg
white cube, sodium carbonate solution and
distilled water. A test tube with an egg white
cube and distilled water.
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12.3
Design an investigation of the action of
digestive enzymes
6 How are you going to record and present the
results?
(Answer varies with Ss.)
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12.3
Design an investigation of the action of
digestive enzymes
7 How can you obtain faster results?
Provide a higher temperature, use smaller egg
white cubes instead of a large one, raise the egg
white cube from the bottom of the test tube by
using a toothpick, etc.
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12.3
Design an investigation of the action of
digestive enzymes
8 How can you make sure that the results are
reliable?
Repeat the experiment a few more times.
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12.3
Design an investigation of the action of
digestive enzymes
9 What precautions should be taken?
Make sure that the egg white cubes are well
covered with the added solution. Handle
hydrochloric acid and sodium carbonate solution
with care because they are corrosive.
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12.3
Design an investigation of the action of
digestive enzymes
Write an experimental report
Objective
To investigate the action of pepsin in protein
digestion.
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12.3
Design an investigation of the action of
digestive enzymes
Procedure
1. Cut the egg white of the hard-boiled egg into
6 small cubes of length 0.5 cm and put 1 in each
of the 6 test tubes.
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12.3
Design an investigation of the action of
digestive enzymes
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12.3
Design an investigation of the action of
digestive enzymes
2. Leave the test tubes in a water bath at 37oC
overnight. 3. Observe and note any changes in the
size and appearance of the egg white cube in each
test tube.
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12.3
Design an investigation of the action of
digestive enzymes
Results
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12.3
Design an investigation of the action of
digestive enzymes
Analysis and discussion
1 From the results obtained, deduce where pepsin
can be found in the digestive system.
Stomach.
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2 Which class of enzymes does pepsin belong to?
Protease.
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12.3
Design an investigation of the action of
digestive enzymes
3 What are produced as a result of protein
digestion by pepsin?
Peptides.
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4 An Albustix paper is dipped into the pepsin
solution. Will the result be positive or
negative? Why?
Positive. Pepsin is a protein and it changes the
colour of the test end of the paper strip.
ANS ?
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12.3
Design an investigation of the action of
digestive enzymes
5 What are the possible sources of errors in this
experiment? Suggest ways for improvement.
(Answer varies with the design.)
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12.3
Design an investigation of the action of
digestive enzymes
Conclusion
Pepsin digests proteins in an acidic medium.
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12.4
Investigation of the effect of bile salts on oil
Questions
1 Explain the differences in results when the oil
is mixed with distilled water instead of bile
salt solution.
Water cannot break down oil into very tiny
droplets as the bile salt solution does.
Therefore, no emulsion /emulsified fluid is
formed and two layers of liquids can be seen.
ANS ?
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12.4
Investigation of the effect of bile salts on oil
Conclusion
What conclusion can you draw from this practical?
Bile salts can break down fats into very tiny
droplets. It is an emulsifying agent.
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12.5
Simulation of digestion and absorption in the
small intestine using a dialysis tubing
Questions
1 Why should we wash the outside of the tubing
thoroughly with tap water before putting it into
the beaker?
Starch molecules on the outside of the tubing
will affect the result. Washing the tubing
ensures no such starch molecules are present.
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12.5
Simulation of digestion and absorption in the
small intestine using a dialysis tubing
2 Why should a small beaker of water be used to
bathe the tubing?
Less water allows a higher concentration of
starch or reducing sugar molecules for easy
detection.
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12.5
Simulation of digestion and absorption in the
small intestine using a dialysis tubing
3 For the following parts of the model, indicate
which parts of the human body they represent.
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12.5
Simulation of digestion and absorption in the
small intestine using a dialysis tubing
4 From the results, which substance is found in
the water surrounding the tubing? Account for its
presence.
Reducing sugar (maltose) is found. Amylase
digests starch into maltose. Maltose molecules
are small enough to pass through the tubing and
diffuse into the surrounding water, (To be
continued.)
ANS ?
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12.5
Simulation of digestion and absorption in the
small intestine using a dialysis tubing
continued from previous page
whereas the large starch molecules are retained
by the tubing.
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12.5
Simulation of digestion and absorption in the
small intestine using a dialysis tubing
5 From the results obtained, why do you think
digestion is needed?
Through digestion, food substances are broken
down into small molecules that can diffuse into
the blood for use in our body.
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12.5
Simulation of digestion and absorption in the
small intestine using a dialysis tubing
6 Comment on the limitations of this model in
demonstrating digestion and absorption in the
small intestine.
Maltose molecules are not small enough to pass
through the small intestine.The small intestine
can secrete enzymes but the model cannot. (To be
continued.)
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12.5
Simulation of digestion and absorption in the
small intestine using a dialysis tubing
continued from previous page
The small intestine shows peristalsis but the
model does not.There are many types of food
molecules in the small intestine apart from
starch.The food molecules have to pass through
more than one layer of cells instead of only one
layer of tubing.The blood is enclosed in blood
vessels.
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12.5
Simulation of digestion and absorption in the
small intestine using a dialysis tubing
7 Suggest some methods to obtain faster results.
Diffusion rate of the reducing sugar molecules
can be increased by stirring the surrounding
water and using a water bath at a higher
temperature. (To be continued.)
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12.5
Simulation of digestion and absorption in the
small intestine using a dialysis tubing
continued from previous page
More concentrated solutions of starch and amylase
can be used to speed up the reaction rate.
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12.1
Relation of diet, eating habit and oral hygiene
to tooth decay
Task 1
1 Tooth decay is more common in molars. Why?
It is because food debris is easily trapped
between the cusps and in the pits. Moreover, the
toothbrush is difficult to reach the molars at
the sides of the jaws to brush off the food
debris.
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12.1
Relation of diet, eating habit and oral hygiene
to tooth decay
2 Will foods rich in starch, such as bread and
crackers, cause tooth decay? Explain your answer.
Yes. Starch is broken down into sugars by the
salivary amylase. These sugars can be used by the
oral bacteria to produce acids.
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12.1
Relation of diet, eating habit and oral hygiene
to tooth decay
3 The dentist suggested Kenny not to eat too
many raisins. Do you know the reasons?
ANS ?
Raisins contain sugars which can be used by the
oral bacteria to produce acids. Raisins are
sticky and they tend to stay on the teeth. The
longer the exposure of the sugary food to the
oral bacteria, the more the acids will be
produced.
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12.1
Relation of diet, eating habit and oral hygiene
to tooth decay
4 How should Kenny change his snacking habit to
prevent tooth decay?
Snack on foods such as milk, cheese or apple that
are good for teeth. Limit the period of time
taking the snack. Reduce the number of snacking
between meals, serve as desserts during meals as
far as possible.
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12.1
Relation of diet, eating habit and oral hygiene
to tooth decay
5 If you were the dentist, what would you suggest
to Kenny for keeping good oral hygiene?
Use dental floss to remove food debris that is
not easily brushed off by the toothbrush. Have a
dental check-up twice a year.
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12.2
Fluoridated water versus fluoride tooth paste
with calcium
Task
1 Suggest why fluoridated water is particularly
beneficial to the low-income people.
The low-income people are less likely to have
regular dental check-up and practise good oral
hygiene by using the oral care products. (To be
continued.)
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12.2
Fluoridated water versus fluoride tooth paste
with calcium
continued from previous page
Drinking fluoridated water is an inexpensive way
to prevent tooth decay.
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12.2
Fluoridated water versus fluoride tooth paste
with calcium
2 In a study carried out in 1999, tooth decay
was shown to decline in both communities with and
without fluoridated water. Can you suggest an
explanation?
The widespread use of fluoride toothpaste. /
Increased awareness of dental health among
people.
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12.2
Fluoridated water versus fluoride tooth paste
with calcium
3 Do you think the addition of calcium to
fluoride toothpaste can offer extra protection?
Yes. It increases the amount of calcium in the
saliva. This drives the equilibrium towards the
replacement of the mineral to the enamel. (To be
continued.)
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12.2
Fluoridated water versus fluoride tooth paste
with calcium
continued from previous page
/ No. The calcium does not stay long in the mouth
to produce an effect.
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12.2
Fluoridated water versus fluoride tooth paste
with calcium
4 Would you suggest fluoridated water or
fluoride toothpaste with calcium to a 3-year old
child? Explain your choice.
Fluoridated water. It offers longer-lasting
protection and is cheap. The child may swallow
the toothpaste if he brushes his teeth with
toothpaste. (To be continued.)
ANS ?
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12.2
Fluoridated water versus fluoride tooth paste
with calcium
continued from previous page
/ Fluoride toothpaste with calcium. It provides
faster protection. Calcium offers extra
protection.
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12.2
Fluoridated water versus fluoride tooth paste
with calcium
5 Do you prefer drinking fluoridated water or
distilled water in relation to the health of your
teeth? Explain your choice.
Fluoridated water. Distilled water has little
fluoride, thus there is a higher chance of
getting tooth decay. (To be continued.)
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12.2
Fluoridated water versus fluoride tooth paste
with calcium
continued from previous page
/ Distilled water. Distilled water is cleaner and
fluoride can still be obtained from other
sources, such as toothpaste and mouth rinse.
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12.3
Activity
Fate of food in our body
Questions
1 Why cannot the whole LEGO cart be passed to the
second group?
The cart is too big to pass through the holes in
the cardboard.
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2 Which process of nutrition does the
disassembling of the LEGO cart into LEGO bricks
represent?
Digestion.
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12.3
Activity
Fate of food in our body
3 Which process of nutrition does the passing of
the LEGO bricks through the holes represent?
Absorption.
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4 Which parts of the LEGO cart cannot be passed
to the second group? State the reason.
ANS ?
The wheels of the cart. They are too big to pass
through the holes in the cupboard and cannot be
disassembled further.
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12.3
Activity
Fate of food in our body
5 How does the first group handle those parts in
4? Which process of nutrition does this represent?
Discard them. This represents egestion.
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6 Which process of nutrition does the building of
the LEGO bricks into new toys represent?
ANS ?
Assimilation.
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12.3
Activity
Fate of food in our body
7 Which part of our body does the cardboard
represent?
The intestinal wall of the small intestine.
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Exercise 12
Multiple-choice questions
D
D
D
B
D
B
A
A
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Exercise 12
Structured questions
1a Draw a labelled diagram of a longitudinal
section of the aching tooth showing the decayed
part and the different structures of the tooth.
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• Correct labels enamel,decay of dentine,gum, pulp
  cavity (0.5m x 4)
• Diagram showing the decayed part reaching the
  pulp cavity (1m)
• Diagram showing the proper stage of the molar
  tooth (1m)
• Neat and tidy drawing (1m)

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Exercise 12
1b i Explain the suggestion of the dentist.
The abrasive in toothpaste helps remove plaque
on teeth (1m). The flouride in toothpaste can
promote the return of calcium and phosphorous to
the enamel so as to strengthen the teeth (1m).
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Exercise 12
1b ii Suggest a way of cleaning the teeth other
than brushing.
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Using dental floss / mouthwash. (Any 1, 1m)
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Exercise 12
1b Manufacturers of sugar-free chewing gums claim
that chewing after meals can prevent tooth decay
because the chewing action can stimulate the
secretion of saliva. Try to relate this to the
process of tooth decay and determine if their
claim is reasonable.
ANS ?
Bacteria act on sugar in plaque to form acids
(1m) which can dissolve the enamel and cause
tooth decay (1m). (To be continued.)
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Exercise 12
continued from previous page
Saliva is slightly alkaline and able to
neutralize the acids produced by the bacteria
(1m). Such claim is reasonable.
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Exercise 12
1d Suggest a reason why tooth decay usually
happens in molars rather than incisors or canines.
It is because the top of the molars of humans
are broad (1m) and have more cusps than incisors
and canines (0.5m). Debris are easily deposited
in the molar and form acids (0.5m). (To be
continued.)
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Exercise 12
continued from previous page
OR Since molars are situated at the back of the
jaw (1m), it is more difficult to clean up the
debris around the molars (1m).
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Exercise 12
2a i Suggest an optimum pH for the enzymes found
in structure A.
pH 2 (1m)
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Exercise 12
2a ii Why is structure A not digested by the
enzymes although it is mainly made of proteins?
It is because there is a mucus lining (1m)
covering the stomach wall (1m). The mucus
protects the stomach from being digested by the
enzymes.
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Exercise 12
2b Name the fluid found in structure B. Give two
functions of it.
Bile. (1m) Bile salts in bile can emulsify fats
into oil droplets (1m). Bile provides an alkaline
medium for the enzymes in the small intestine
(1m).
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Exercise 12
2c Structure C has special features adapted to
food absorption. What are these features?
The finger-like villi greatly increase the
surface area for absorption (1m). The epithelium
of the villi is only one-cell thick which allows
rapid diffusion (1m). The presence of blood
capillaries and lacteal allow the absorbed food
to be carried away rapidly (1m).
ANS ?
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Exercise 12
2d Name one food substance that can stimulate the
movement of D. What happens to the man if it is
insufficient in his diet?
Dietary fibre (1m). Constipation will occur (1m).
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Exercise 12
3a What is the function of gall bladder in the
digestion of food?
ANS ?
It temporarily stores the bile produced from the
liver (1m) and releases the bile into the
duodenum if needed for emulsification of fats
(1m).
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Exercise 12
3b As a friend of David, what will you advise him
of his future diet? Give your reasons.
He should eat less / avoid fatty foods (1m). As
bile cannot be released normally from the gall
bladder, the fats is not digested properly which
may cause digestive disorders (1m).
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Exercise 12
3c To convince David to take your advice, explain
to him how fats will be digested in his body
after the operation.
After the operation, fats will still be
emulsified into oil droplets by bile first.
However, the bile is directly released from the
liver and the effectiveness of emulsification is
reduced (1m). (To be continued.)
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Exercise 12
continued from previous page
The oil droplets will then be digested by the
lipase in pancreatic juice (1m), forming fatty
acids and glycerol (1m).
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Exercise 12
3d Which of the following foods is most suitable
for David a few days after the operation? Explain
your choice.
The glucose beverage is most suitable for David
(1m). It is because glucose can be readily
absorbed by the body (1m). The other two foods
contain much fats which put a heavy burden to the
digestive system of David (1m).
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