The document discusses different nutrients including carbohydrates, proteins, and fats. It describes the chemical composition and tests used to identify these nutrients. Carbohydrates include monosaccharides like glucose, disaccharides like sucrose, and polysaccharides like starch. Proteins are made of amino acids linked together, while fats contain fatty acids and glycerol. Tests described include Benedict's test for reducing sugars, iodine test for starch, and Biuret test for proteins. The document provides information on the nutrients present in different foods.

1. Nutrients

2. • List the chemical elements which make up
carbohydrates, fats and proteins (Pure)
• Describe and carry out tests for starch,
reducing sugars, proteins and fats
• State that large molecules are synthesised
from smaller basic units
• State the roles of water in living organisms
Learning Outcome

3. What is in the food we eat?

4. What are the different Nutrients?
Carbohydrates
Proteins
Fats
Water

5. Carbohydrates
Fructose
Glucose
Sucrose
These are some examples of carbohydrates.
What do they all have in common?
Starch

6. General formula: CnH2nOn
•Mono : 1  Monosaccharides
• Eg: Glucose, fructose, galactose
•Di : 2  Disaccharides
• Eg: Maltose, sucrose, lactose
•Poly : Many  Polysaccharides
Carbohydrates

7. Monosaccharides (Single sugar)
Single sugar Occurrence
Glucose
Fructose
Galactose
Found in all animals
Common in plants, but
rare in animals
Present in milk sugar
from mammals

8. Disaccharides (Double Sugars)
Double sugars Occurrence
Maltose
Sucrose
Lactose
Found in cereal
Found in cane sugar
(common table sugar)
Present in milk sugar
from mammals

9. Polysaccharides
Many smaller basic units of glucose
joined together to form polysaccharides.

10. Polysaccharides (Complex Sugars)
Complex sugars Occurrence
Starch
Storage form of
carbohydrate in plants
Glycogen •Storage form of
carbohydrate in animals
•Stored mainly in liver and
muscles
Cellulose
Structural form of
carbohydrate in plants

11. glucose
maltose
starch

12. • Can starch diffuse
through the partially
permeable membrane?
• Can glucose diffuse
through the partially
permeable membrane?

13. Permeability
• Monosaccharides are small sugar molecules that
can pass through the visking tubing.
• Disaccharides and polysaccharides are large,
complex molecules that CANNOT pass through
the visking tubing.

14. Testing for Reducing Sugars
(Benedict’s Test)
About 2cm3 of
test solution
(In this case:
reducing
sugars e.g.
glucose)
Heat in water bath
Brick- Red
precipitate
Add an equal
amount of
Benedict’s
solution

15. Benedict’s Test for
Reducing Sugar
Step 1: Add 2cm³ of Benedict’s solution to
2cm³ of sample. Shake well to mix.
Step 2: Place test tube in a water bath
containing boiling water for 5 mins.
Step 3: Observe the change in colour and
record your observations.

16. Benedict’s Test for
Reducing Sugar
Colour Change Conclusion
Remains blue Reducing sugar absent
Blue to brick-red precipitate Reducing sugar
PRESENT

17. Benedict’s Test :
can be used to find out the amount of reducing sugar
Brick-
red ppt
Orange
red ppt
Green / yellow
ppt
Blue
solution
None Traces of
reducing sugar
Moderate Large
amount of
reducing
sugar

18. Benedict’s Test Results
Brick-
red ppt
Orange
red ppt
Green / yellow
ppt
Blue
solution

19. Iodine test for Starch
Step 1: Add a few drops of iodine solution to
sample on a white tile
(note: iodine solution = iodine + potassium iodide
solution)
Step 2: Observe and record your observations.
Colour Change Conclusion
Remains brown Starch absent
Brown to blue-black colour Starch
PRESENT

20. Iodine test
results
Positive (+)
Negative (-)

21. Fats / Lipids (Pure)
• Organic compounds made up of carbon,
hydrogen and oxygen.
• No general formula for fats.
• Found in butter, cheese,
fatty meat, nuts, oil etc.

22. Fats
Formed from smaller basic units of
fatty acids and glycerol.

23. Oil droplet
Add 2cm3 of
ethanol
Add 2cm3 of
water
Shake mixture
thoroughly
White
emulsion
2 layers of
immiscible
liquid
Test for oil/ fats
Ethanol/ Alcohol Emulsion test

24. Ethanol Emulsion Test
For liquid food:
Step 1: Add 2cm3 of ethanol to a few drops of the
sample. Shake the mixture well for about 5 mins.
Step 2: Add 2cm3 of water to the mixture and shake
it.
Step 3: Observe and record observations.
Observation Conclusion
Solution remains clear Fats absent
Cloudy white emulsion Fats PRESENT

25. For solid food:
Step 1: Cut the sample into small pieces and place the
pieces in a test tube.
Step 2: 2cm3 of ethanol is added. Shake
well for 5 mins.
Step 3: Allow the solid particles to settle.
Step 4: Decant ethanol portion to another test
tube containing 2cm3 of water.
Solid particles
Ethanol
Only pour off
the top layer
of ethanol

26. Kwashiorkor
Severe protein-energy malnutrition

27. Proteins
• Organic substances made up of carbon, hydrogen,
oxygen and nitrogen
• Sulfur may also be present

28. Proteins are built from….
Proteins are built up from smaller basic units
of amino acids
Many amino acids
linked together to form
Polypeptide / peptone.

29. Polypeptide
Folding of this long chain of amino acids to
give a unique three-dimensional shape
Protein is formed
From Polypeptides  Proteins

30. Sample to
be tested:
in this case,
Egg white
(2cm3)
Add 1cm3 of
NaOH
Add 1%
CuSO4 drop
by drop
Shake mixture
thoroughly
Shake after
each drop
Allow
mixture to
stand for
5min
Violet colour
click
Testing for Proteins
(Biuret test) – 1st method

31. Step 1: Add 1 cm3 of sodium hydroxide solution to 2 cm3
of sample. Shake well.
Step 2: Add 1% copper(II) sulfate solution, drop
by drop, gently shaking after each drop
Step 3: Observe and record observations
Colour Change Conclusion
Remains blue Proteins absent
blue to violet Proteins PRESENT
Testing for Proteins
(Biuret test) – 1st method

32. Test for Proteins
(Biuret test) – 2nd method
Sample to
be tested:
in this case,
Egg white
(2cm3)
Add 2cm3 of
Biuret solution
Shake mixture well
Allow
mixture to
stand for
5min
Violet colour

33. Biuret Test for Proteins
(2nd Method)
Biuret solution = sodium hydroxide + copper(II)
sulphate solution
Step 1: Add 2 cm3 of Biuret solution to 2 cm3 of
the sample. Shake well.
Step 2:Observe and record observations after 5
minutes.
Colour Change Conclusion
Remains blue Proteins absent
blue to violet Proteins PRESENT

34. Summary

35. Based on these results, which one of the following
conclusions about the food is correct?
Micro Ques 1
( D )
Proteins
Reducing
Sugars
Starch
A
Absent Absent Absent
B
Absent Absent Present
C
Absent Present Absent
D
Present Absent Present

36. The table below shows the chemical elements present in
each of the four substances. Which substance, A, B, C or D
could be a protein?
Micro Ques 2
( C )
Substance Carbon Hydrogen Nitrogen Oxygen
A    
B    
C    
D    

37. Milk produces a red precipitate when heated with Benedict's
solution.
A purple colour develops when the biuret test is used on milk.
Using these results only, which nutrients does milk contain?
Micro Ques 3
( C )
A Fat and protein
B Fat and starch
C Reducing sugar and protein
D Reducing sugar and starch