sains bab 2

CHAPTER 2 Nutrition
2.1 Tests for starch, sugar, protein and fats Analysing the classes
Experiment of food


Aim To test for starch, sugar (glucose), protein and fats Date:


NOTESOTES
Apparatus/Materials Test tubes, Bunsen burner, tripod stand, wire gauze, droppers, N
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beaker (250 cm ), filter paper, measuring cylinder, 1% starch solution, 1% glucose
solution, albumin solution, coconut oil, Benedict’s solution, iodine solution, Millon’s Science Titbits
reagent, ethanol (ethyl alcohol) Glucose is a soluble
carbohydrate while
starch is an insoluble
Instructions and Observations carbohydrate.
Carbohydrates are
Instructions Observation important because they
provide energy and
[A] Test for starch Starch solution heat to maintain the
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1. Pour 1 cm of 1% starch dropper body temperature.
solution into a test tube. turned dark blue.
2. Add a drop of iodine
solution to the starch iodine drop Observing
Analysing
solution.
3. Observe and record the
change in colour. 1% starch
solution
Science Titbits
Proteins are important
for growing children
[B] Test for sugar (glucose) A brick-red because they build the
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1. Pour 2 cm of 1% glucose body.
solution precipitate was
glucose solution into a + Proteins are used for
test tube. water Benedict's formed synthesising enzymes,
2. Add an equal amount of beaker solution hormones and

Benedict’s solution to XXXXXXXXXXXXX wire gauze antibodies.
the glucose solution. tripod
stand Bunsen burner The amount of energy
Observe the colour of
produced by one
the mixture. gramme of fat is twice
3. Put the test tube into a that produced by one
water bath for 2 to 3 minutes to heat the mixture. gramme of
4. Remove the test tube from the water bath. Observe and record carbohydrate.
the change in colour.
Fats act as heat
insulators, solvents for
vitamins A, D, E and K
[C] Test for proteins A white precipitate and make up the
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1. Pour 2 cm of albumin was formed which structural components
of the cell membrane.
solution into a test tube.
albumin
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2. Add 1 cm of Millon’s reagent water solution turned brick red Seals found in the
to the albumin solution. + Arctic seas have a thick
Millon's when heated.
3. Observe and record what reagent layer of fat called
happens. ‘blubber’ for heat
insulation.
4. Heat the test tube inside a
Bunsen tripod
water bath for 1 to 2 burner stand
minutes.
5. Observe and record any
change in colour.

Science Process Skills Science Manipulative Skills
• Observing 17 • Using and handling scientific apparatus and materials correctly
• Interpreting data • Keeping scientific apparatus and materials correctly and safely

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Instructions Observation NOTESOTES
[D] Test for fats translucent Science Titbits
spot Translucent spot
(a) Spot test A B remained on A but Benedict’s solution can
1. Fold a filter paper into two filter be used to detect the
paper presence of sugar in
halves, A and B. not on B.
urine to determine
2. Put a drop of coconut oil on whether a person has
A and a drop of water on B. diabetes.
Allow them to dry.
3. Hold the filter paper against Web Guide
the light. Nutrition
4. Observe and record your http://en.wikipedia.org/
observations. wiki/Nutrition
(b) Emulsion test A clear solution was
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1. Pour 3 cm of ethanol in a test Ethanol is formed when Science Titbits
tube. inflammable. Animal fats are rich in
2. Add 4 to 5 drops of coconut oil Make sure there is coconut oil was cholesterol which can
to the ethanol. no flame around. be deposited in arteries
3. Close the mouth of the test tube added to ethanol. A and can cause blockage
with your thumb. Shake the milky solution in blood flow. This may
mixture and then allow it to stand (emulsion) was result in heart diseases
and high blood
for 2 minutes. pressure. It is advisable
4. Observe and record the change in the mixture. formed when the to use vegetable oils
5. Add 5 to 6 drops of the mixture into a test tube containing mixture was added to like palm oil for
water. Close the mouth of the test tube with your thumb. Shake cooking because it is
low in cholesterol.
the mixture, allow it to stand and observe. water.






Discussion

1. What is the colour of the iodine solution?
Light brown

2. What happens to the colour of the glucose and Benedict’s solution mixture after
heating?
The colour changes from blue to brick red.
Attributing
3. What happens when coconut oil is added to ethanol?
The coconut oil dissolves in ethanol.
Attributing
4. Why does the water turn milky when the mixture of coconut oil and ethanol is
added?
The coconut oil is insoluble in water and forms tiny droplets (an emulsion).
Attributing
5. When some crushed peanuts are rubbed on a piece of white paper, translucent
grease marks are formed. What inference can you make about the contents of the
peanuts?
The peanuts contain fats.
Making inferences
Conclusion

dark blue
1. Iodine solution turns starch solution to .
Drawing conclusions

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2. When a glucose solution mixed with Benedict’s solution is heated, a N
NOTESOTES
brick-red precipitate
is formed.
white precipitate
3. When albumin is heated with Millon’s reagent, the formed
brick red
turns .
emulsion
4. An is produced when oil is added to water.



CHAPTER 2 Nutrition
2.2 Enzyme action Experiment Understanding the
human digestive
system

Aim To show the action of the enzyme in saliva on starch Date:


Variable that

(a) is kept constant Amount of starch solution, time period
(b) is manipulated Food content of test tubes Observing
Analysing
(c) responds End product of enzyme action

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Apparatus/Materials Test tubes, beakers (250 cm , 100 cm ), measuring cylinder
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(10 cm ), thermometer, Bunsen burner, tripod stand, wire gauze, dropper, test tube Science Titbits
holder, distilled water, 1% starch solution, iodine solution, Benedict’s solution, saliva Digestion begins in the
mouth and ends in the
small intestine.
Instructions
The end products of
1. Rinse your mouth with water. digestion are glucose,
2. Collect your saliva in a small amino acid, fatty acid
beaker. and glycerol.
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3. Pour 2 cm of the saliva into two test tube B Enzymes work best at
test tubes, A and B.
the optimum
4. Heat test tube A over a small temperature of 37 °C.
flame for 1 minute until it boils They become inactive
and then, allow it to cool. when the temperature is
test tube test tube C
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5. Pour 2 cm of distilled water A low and are killed
when the temperature
into a test tube, C.
warm water becomes too high.
6. Place all the three test tubes
(37 C)
0
in a warm water bath (37 °C) Glossary
for 5 minutes. Figure 2.2
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7. After 5 minutes, add 2 cm of Enzyme
An organic catalyst
starch solution each into test tubes A, B and C and stir the mixture. which quickens the
8. Remove a small sample from each test tube to test for starch and glucose. chemical reactions in
9. After 20 minutes, test samples from each test tube again for starch and glucose. the body.
10. Record your results. Peristalsis
Waves of muscular
contraction and
Procedure relaxation which occur
in the oesophagus that
1. The mouth was rinsed with water. helps to move food
down to the stomach.
2. Saliva was collected in a small beaker.
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3. 2 cm of the saliva was poured into two test tubes, A and B.

Science Process Skills Science Manipulative Skills
• Observing 19 • Using and handling scientific apparatus and materials correctly
• Interpreting data • Keeping scientific apparatus and materials correctly and safely

NOTESOTES
4. Test tube A was heated over a small flame for 1 minute until it boiled. Then it was N
allowed to cool. Science Titbits
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5. 2 cm of distilled water was poured into a test tube, C. The hydrochloric acid
inside the stomach not
6. All the three test tubes were placed in a warm water bath (37 °C) for 5 minutes. only provides an acidic
medium for the
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7. After 5 minutes, 2 cm of starch solution was added to test tubes A, B and C enzymes protease and
lipase to act, but also
and the mixture was stirred. kills any bacteria
8. A small sample was removed from each test tube to test for starch and glucose. present.

9. After 20 minutes, samples from each test tube were tested again for starch and Glucose and maltose
are called reducing
glucose. sugars which give
positive results with the
10. Results were recorded. Benedicts’s test while
sucrose is a non-
reducing sugar which
Results does not.


Test tube A Test tube B Test tube C
Test
Beginning End Beginning End Beginning End


Iodine Presence Presence Presence Presence Presence Presence
solution of starch of starch of starch of starch of starch of starch

Benedict’s Absence Absence Absence Presence Absence Absence
solution of sugar of sugar of sugar of sugar of sugar of sugar


Discussion

1. Why is the mouth rinsed first before saliva is collected?
To make sure there is no food debris in the saliva collected.
Analysing

2. Why is the water bath kept at 37 °C?
Our body temperature and the optimum temperature for enzyme action is 37 °C.
Making inferences

3. What happens to the starch in test tube B?
The starch is digested and changed into sugar (maltose).
Analysing

4. Why is there no change in the starch in test tube A?
Heating has killed the enzyme.
Making inferences
5. What is the purpose of setting up test tube C?
To act as a control experiment
Analysing
Conclusion

amylase digests
The enzyme present in saliva starch and
sugar (maltose) killed Drawing conclusions
converts it into . The enzyme is when saliva is
boiled.




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CHAPTER 2 Nutrition
2.3 The process of absorption of digested Understanding the
food Observation process of absorption
of digested food
Aim To study the movement of digested food through a Visking tube Date:


Instructions NOTESOTES
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1 Figure 2.3(a) shows a Visking tube of
1% starch solution placed in boiling Visking tube Science Titbits
tube A which contains distilled water. Maltose is a sugar made
Figure 2.3(b) shows another Visking glucose up of two molecules of
tube containing 1% glucose solution solution glucose. It is broken
down into glucose by
immersed in boiling tube B which starch solution the enzyme amylase.
contains distilled water.
2. Some distilled water is removed from Glossary
distilled
each boiling tube with a dropper and water Diffusion
tested for starch and glucose. The movement of solute
3. After 15 minutes, the tests are repeated. boiling tube A boiling tube B molecules from an area
4. Record any colour change in each of high concentration to
boiling tube. (a) (b) an area of lower
concentration through a
Figure 2.3
semipermeable
membrane.
Results


Tests Boiling tube A Boiling tube B

Beginning Brownish colour Brownish colour
Iodine test
After 15 minutes Brownish colour Brownish colour

Beginning Blue Blue

Benedict’s
After 15 minutes Blue Blue to green and
test
then to a brick-red
precipitate


Discussion

1. Why are the Visking tubes washed before put into the boiling tubes?
To ensure that there is no starch or glucose solution present on the outer surface
Analysing
which might affect the results of the experiment.
2. What does the Visking tube represent?
The small intestine in the body
Making analogies
3. Which substance can diffuse out of the Visking tube?
Glucose
Attributing
4. What inference can be made about the size of the starch and glucose molecules?
The starch molecules are big while the glucose molecules are small.
Making inferences
Science Process Skills Science Manipulative Skills
• Observing 21 • Using and handling scientific apparatus and materials correctly
• Interpreting data • Keeping scientific apparatus and materials correctly and safely

5. In the human body, what process takes place to change large molecules into N
NOTESOTES
smaller molecules for absorption?
Digestion through enzyme action
Analysing
Conclusion

glucose molecule starch molecule
The which is smaller than the can
Drawing conclusions
diffuse out through the Visking tube.







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Each question is followed by four possible answers. Choose the correct answer or the one that is the most suitable.


1. Which class of food is found in 5. A group of students carried out A osteomalacia
abundance in rice? three tests on food X and obtained B scurvy
A Carbohydrate the following results. C kwashiorkor
B Protein D anaemia
C Fats Test Observation
D Vitamins Iodine solution Turns to dark 8. Which of the following is
blue correctly matched?
For Questions 2 and 3,refer to the
information below. Benedict’s A brick-red Vitamin Source Function
solution precipitate is
• Required in small amounts by formed A C Citrus For healthy
our body Millon’s reagent No change fruits teeth and
• Some are soluble in fats gums
• Found in fruits and vegetables B K Milk For strong
Which of the following
conclusion is correct? bones and
2. Which class of food suits the A Food X contains sugar and teeth
information given? protein. C A Yeast For cellular
A Carbohydrate B Food X contains protein and respiration
B Protein fats.
C Vitamins C Food X contains starch and D B Eggs For
D Minerals protein. clotting
3. What is the function of the class D Food X contains starch and of blood
of food indicated? sugar.
9. What are the minerals found in
A To supply energy
6. Energy-supplying food include milk, cheese and eggs?
B To build enzymes and
I carbohydrates I Calcium
hormones
II proteins II Iodine
C To keep the body healthy
III fats III Phosphorus
D To prevent constipation
A I and II only A I and II only
4. If Mary does not eat any seafood, B I and III only B I and III only
what is she likely to suffer from? C II and III only C II and III only
A Rickets D I, II and III D I, II and III
B Goitre
C Anaemia 7. A child who lacks proteins in his 10. Which of the following statements
D Constipation diet may suffer from about water is correct?


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I It acts as a solvent. 13. Where does the absorption of X Y
II It is a medium of transport. digested food take place?
III It helps to maintain body A Q C S A Amylase Lipase
temperature. B R D T B Amylase Pepsin
A I only
14. Which of the following C Trypsin Protease
B I and II only
statements about bile is correct? D Lipase Protease
C II and III only
I It is produced in the stomach.
D I, II and III
II It assists in the breakdown of 18. Gastric juice in the stomach
11. A person’s balanced diet is fats. contains
determined by his III It is stored in the gall bladder. I water III protease
I age A I and II only II hydrochloric acid
II sex B I and III only A I and II only
III occupation C II and III only B I and III only
A I and II only D I, II and III C II and III only
B I and III only 15. Energy released from food is D I, II and III
C II and III only measured in 19. What is the function of the large
D I, II and III I calories III kilojoules intestine?
II watts A Final digestion of food
For Questions 12 and 13,refer to
A I and II only B Absorption of digested foods
Figure 1.
B I and III only C Breakdown of fatty foods
C II and III only D Reabsorption of water
12.
D I, II and III
20.
16. Milk is digested in the
P
I mouth P
II stomach Q
III small intestine R
A I and II only
T B I and III only S
T
Q C II and III only
D I, II and III Figure 2
R
17. Figure 2 shows part of the
S X
Starch maltose digestive system. Where is the
Y bile produced and stored?
Protein polypeptide Produced Stored
Figure 1
A P Q
Figure 1 shows the digestive The information given shows the
tract in humans. Where are digestion of starch and protein by B R S
carbohydrates digested? enzymes, X and Y. Which of the C Q S
A P and Q C R and S following pair of enzymes is
B P and R D S and T correct? D P T





1. Complete the following table.

Class of food Source Deficiency disease

Protein Fish Kwashiorkor

Iodine Seaweed Goitre

Vitamin A Carrots Night blindness

Phosphorus Cheese Brittle bones



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2. Figure 3 shows the human digestive tract.




A


B

D
C
E

G
F



Figure 3
(a) Name the different alimentary organs labelled A to G.
Mouth Pancreas
(i) A : (iv) E :
Oesophagus Small intestine
(ii) B : (v) F :
Stomach Large intestine
(iii) C : (vi) G :
Liver
(iv) D :
(b) State two processes that occur in organ A.
Chewing of food and digestion of carbohydrate

(c) Name the substance produced by D and state its function.
Bile. It breaks large fat droplets into smaller particles for the enzyme lipase to act on.
(d) What action helps food to move along B to C?
Peristalsis

(e) Name the enzymes produced by the pancreas. For each enzyme, name the substrate
it acts on and the end products.
Amylase which acts on starch and changes it into glucose.
(i)
Protease which acts on proteins and changes them into amino acids.
(ii)
Lipase which acts on fats and changes them into fatty acids and glycerol.
(iii)
(f) Besides digestion, what else takes place in F?
Absorption of digested food

(g) What is absorbed in G?
Water



















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