2. Learning Outcomes
– 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
5. Carbohydrate (Pure)
– Organic compounds made up of
carbon, hydrogen and oxygen.
– The general formula is CmH2nOn
– Glucose is C6H12O6
– Food sources: Rice, bread, pasta etc.
6. Types of Carbohydrates
Mono: 1; Di: 2; Tri: 3; Poly: many
• Monosaccharides (single-unit sugar)
– Glucose, fructose and galactose
• Disaccharides (double-unit sugar)
– Maltose, sucrose and lactose
• Polysaccharides (many-units of sugar)
– Starch, glycogen and cellulose
7. All of you are seated at
your individual seats…
Imagine all of you are
simple sugars…
I am one
molecule of
glucose.
8. Monosaccharides (Single sugar)
Single sugar Occurrence
Glucose Found in all animals
Common in plants,
Fructose
but rare in animals
Present in milk sugar
Galactose from mammals
9. Disaccharides (Double Sugars)
Double sugars Occurrence
Found in sprouting
Maltose
grains
Found in cane sugar
Sucrose (common table
sugar)
Lactose Present in milk sugar
from mammals
11. 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
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. What are reducing
sugars?
• Sugars that can produce a brick-red
precipitate when boiled with Benedict’s
solution are called reducing sugars.
• ALL monosaccharides are reducing sugars.
• Glucose, maltose and lactose are examples of
reducing sugars.
• Sucrose is NOT a reducing sugar.
15. Test for Reducing Sugars
(Benedict’s Test)
Add an equal
amount of
Benedict’s
solution
About 2cm3 of
test solution
(In this case:
reducing
sugars e.g.
glucose) Brick- Red
precipitate
Heat in water bath
16. 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.
17. Benedict’s Test for
Reducing Sugar
Colour Change Conclusion
Remains blue Reducing sugar absent
Blue to brick-red Reducing sugar
precipitate PRESENT
18. Benedict’s Test –
Quantitative Test
Amount of Reducing
Colour Change
Sugar Present
Traces of reducing
Blue to green mixture
sugar
Blue to yellow or orange Moderate amount of
precipitate reducing sugar
Blue to brick-red or Large amount of
orange-red precipitate reducing sugar
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 Starch
colour PRESENT
20.
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.
24. Test for Oil/ Fats
(Ethanol/ Alcohol Emulsion Test)
Add 2cm3 of Add 2cm3 of
ethanol water
Shake mixture
thoroughly 2 layers of
White immiscible
Oil droplet emulsion liquid
click
25. 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
26. 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.
27. Decant
Ethanol
Only pour off
the top layer
of ethanol
Solid particles
28. For solid food:
Step 5: Observe and record your observations.
Observation Conclusion
Remains clear Fats absent
Cloudy white emulsion Fats PRESENT
32. Amino acids to polypeptide
Many amino acids
linked together to form
polypeptide.
33. Polypeptide to proteins
Polypeptide
Folding of this long chain of amino
acids to give a unique three-
dimensional shape
Protein is formed
http://intro.bio.umb.edu/111-112/111F98Lect/folding.html
35. Test for Proteins
(Biuret test) – 1st method
Allow
Add 1%
Add 1cm3 of mixture to
CuSO4 drop
NaOH stand for
by drop 5min
Sample to Shake mixture Shake after
be tested: thoroughly each drop
in this case, Violet colour
Egg white
(2cm3)
click
36. Biuret Test for Proteins
(1st Method)
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
37. Test for Proteins
(Biuret test) – 2nd method
Allow
Add 2cm3 of mixture to
Biuret solution stand for
5min
Sample to Shake mixture well
be tested:
in this case, Violet colour
Egg white
(2cm3)
click
38. 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
41. Functions of Water
Water is a main solvent used in the
body to dissolve substances.
1. Transport of dissolved substances
around body
– Digested food from small intestine to
other parts of the body
– Waste products from cells to excretory
organs for removal
– Hormones from glands to different parts
of the body as required
42. 2. Key component of
– Protoplasm
– Digestive juices
– Blood
– Tissue fluid
3. Control body temperature (cools body during
evaporation of sweat)
4. Required for chemical reactions to take place in.
Eg. digestion
!!! Prevent dehydration is NOT a function of water
43. Functions of Water in Plants
1. Raw material for photosynthesis
2. Maintain the turgidity of plant cells in order
to keep the plant upright
3. Transport of mineral salts from roots to
leaves via xylem
4. Transport food substances from leaves to
other parts of plants via phloem
