1) The document discusses nutrients and their importance for organisms. It focuses on carbohydrates, fats, and proteins. 2) Carbohydrates include sugars, starches, and fibers and serve as energy sources. They are broken down through hydrolysis. Fats also provide energy and insulation. Proteins are made of amino acids and are essential for growth and repair. 3) Tests are described to identify carbohydrates, sugars, and fats in food. The properties and functions of nutrients are explained at the molecular level.

1. Topic 3: Chapter 4
NutrientsNutrients –– Part 1Part 1
The needThe need
for foodfor food
++
CarbohydraCarbohydra

2. Chemicals and Reactions that
take place in the cell.
• Living organisms contains huge amount of
Macromolecules (large molecules)
• Chemical activities that take place in a cell is
known as metabolism.
• Metabolic reactions are categorized as anabolic
reactions and catabolic reactions.

3. Anabolic & Catabolic
Reactions
• Anabolic reactions build up large molecules
from simple molecules.
• Catabolic reactions break down larger
molecules into smaller molecules.

4. Illustration of Anabolic &
Catabolic Reactions
H20 Nitrate Phosphate
Sunlight
CO2
Carbohydrates
(e.g. Glucose)
Photosynthesis

5. Illustration of Anabolic &
Catabolic Reactions
Nitrate Phosphate
Lipids
Carbohydrates
(e.g. Glucose)
Protein
Eat
Digestion
Absorption

6. Why do organisms need
food?
1) To provide energy for the vital activities of
the body via respiration.
 Physical movement, Digestion, Excretion, etc.
2) To synthesize new protoplasm – for growth
& repair, & for reproduction.
3) To maintain good health – prevent
deficiency disease.
 Vit. C, Calcium, etc.

7. Nutrients
• Chemical substances in food that nourish the body.
• They provide energy & raw materials needed by
the body.
(A) Organic Nutrients(A) Organic Nutrients
(Contains Carbon)(Contains Carbon)
(A) Organic Nutrients(A) Organic Nutrients
(Contains Carbon)(Contains Carbon)
(B) Inorganic Nutrients(B) Inorganic Nutrients
(does not contain Carbon)(does not contain Carbon)
(B) Inorganic Nutrients(B) Inorganic Nutrients
(does not contain Carbon)(does not contain Carbon)
1)1) CarbohydratesCarbohydrates
2)2) FatsFats
3)3) ProteinsProteins
4)4) VitaminsVitamins
5)5) Dietary FibreDietary Fibre
1)1) WaterWater
2)2) Mineral SaltsMineral Salts

8. A(1): Carbohydrates
• Organic compounds made up of the
elements carbon (C), hydrogen (H) &
oxygen (O).
• The hydrogen & oxygen atoms are
present in the ratio 2:1.
• Generalized formula: CnH2mOm.

9. A(1): Functions of Carbohydrates
a) as a substrate for respiration
 provide energy for cell activities
a) to form supporting structures
 e.g. plant cell walls
a) to be converted to other organic compounds
such as amino acids and fats
b) for the formation of nucleic acid
 e.g. DNA
a) to synthesize lubricants
 e.g. mucus – Carbo + Protein)
a) to produce the nectar in some flowers

10. A(1): Sources of Carbohydrates
•Broken down quickly to provide
energy for the body
• Found naturally in food (Fruits,
Milk, etc.)
• Found in processed or refined
food ( Candy, Syrup, etc.)
•Lack Vitamins, Minerals & Fibres
•Made of sugar molecules strung
together in long complex chains
• Majority of carbohydrates are
from complex carbohydrates
and naturally occurring sugars.
•Provides Vitamins, Minerals &
Fibres

11. A(1): Groups of Carbohydrates
CarbohydratesCarbohydrates
Polysaccharides
(complex carbohydrates)
Polysaccharides
(complex carbohydrates)
Disaccharides
(double sugars)
Disaccharides
(double sugars)
Monosaccharides
(single sugars)
Monosaccharides
(single sugars)
e.g. glucose
fructose,
galactose
e.g. glucose
fructose,
galactose
e.g. starch,
glycogen,
cellulose
e.g. starch,
glycogen,
cellulose
e.g. Sucrose,
Maltose,
Lactose
e.g. Sucrose,
Maltose,
Lactose

12. • Simple sugars, sweet
• Smallest basic unit.
• ALL with general formula C6H12O6.
- But differ in arrangement of atoms in
molecules.
Monosaccharides
(single sugars)
Monosaccharides
(single sugars)

13. Disaccharides
(double sugars)
Disaccharides
(double sugars)
• Simple sugars, sweet
• Formed when 2 monosaccharides are
joined together by condensation.
• ALL with general formula C12H22O11.

14. Condensation
• Chemical reaction in
which
• A water molecule is
needed
• to break up a complex
molecule into smaller
molecules
• Chemical reaction in
which
• A water molecule is
needed
• to break up a complex
molecule into smaller
molecules
• Chemical reaction in
which
• 2 simple molecules are
joined together to
form a larger molecule
• with the removal of
water
• Chemical reaction in
which
• 2 simple molecules are
joined together to
form a larger molecule
• with the removal of
water
Hydrolysis

15. Condensation: Formation of
LactoseLactose
• occurs naturally in milk (milk sugar).
• broken down by the enzyme “lactase” during
digestion to yield glucose and galactose by hydrolysis
• When milk sours, bacteria converts lactose to lactic
acid

16. Condensation: Formation of
Maltas
e
Maltas
e
• Malt Sugar
• Important component in the process of fermenting
barley that can be used for brewing beer.
• broken down by the enzyme “maltase” during
digestion to yield 2 glucose molecules by hydrolysis

17. Condensation: Formation of
Sucros
e
Sucros
e
• occurs naturally in sugarcane (cane sugar), sweet
fruits, honey and certain storage roots (e.g. carrots).
• Not found in mammals

18. Hydrolysis: Breaking down of
Sucros
e
Sucros
e
+
enzyme
glucose fructosesucrose water
+
• broken down by the enzyme “sucrase” /
“invertase” during digestion to yield glucose and
fructose by hydrolysis

19. Polysaccharides
(complex carbohydrates)
Polysaccharides
(complex carbohydrates)
• Consists of many monosaccharide
molecules joined together by
condensation.
• Starch, Glucogen and Cellulose are
complex carbohydrates which are made
up of numerous glucose molecules
condensed together.

20. starch
Polysaccharides
(complex carbohydrates)
Polysaccharides
(complex carbohydrates)
Starch
Starch
• Long straight or
branched chains
of glucose
molecules
• Made and
stored in plants
but not in
animals

21. starch
Polysaccharides
(complex carbohydrates)
Polysaccharides
(complex carbohydrates)
Cellulose
Cellulose
• Long straight chains
of glucose molecules
• But different
linkages from starch.
• Main part of plant
cell wall
• Forms fibre in the
diet of mammals

22. starch
Polysaccharides
(complex carbohydrates)
Polysaccharides
(complex carbohydrates)
Glycogen
Glycogen
• Highly branched
chains of glucose
• Made and stored
in animals and
fungi but not in
plants

23. Storage Glucose
• Starch
• Stored in leaves, tubers and roots
Plants
Animals
• Gycogen
• Stored mainly in liver and muscles

24. Glycogen and Starch
as storage materials
• Insoluble in water
 do not change the water potential in cells
• Large molecules
 Unable to diffuse through cell membranes
• Easily hydrolysed to glucose when needed
 e.g for tissue respiration
• Compact shapes which occupies less space.

25. Hydrolysis and Condensation
maltase maltase maltase maltase
Starch (in plants)Starch (in plants)
MaltoseMaltose
GlucoseGlucose
Hydrolysis in the
mouth
Hydrolysis in the guts
by enzyme maltase
Condensation in the liver
Glycogen (in animals)Glycogen (in animals)
Consumed and
undergoes
Digestion
Digestion
Glucogenesis

26. Food Test (1)Food Test (1)
Test for Starch – Iodine TestTest for Starch – Iodine Test
Procedure:
• Add 1-3 drops of iodine solution onto any
substance.
Results:
• If starch is present, the iodine solution
changes from yellowish brown to blue-black
colour.

27. Food Test (2)Food Test (2)
Test for Reducing Sugars – Benedict’sTest for Reducing Sugars – Benedict’s
TestTest
Reducing Sugars:Reducing Sugars:
Glucose, Fructose, Maltose, Lactose
Procedure:Procedure:
1. Add 2 cm3
of Benedict’s solution to
equal volume of test solution.
2. Mix the solutions by shaking.
3. Heat the mixture in a boiling water-
bath for 5 minutes.
4. Prepare a control using distilled water
instead of the test solution Benedict’s solution

28. Food Test (2)Food Test (2)
Test for Reducing Sugars – Benedict’sTest for Reducing Sugars – Benedict’s
TestTest
Results
Colour change
Amount of reducing sugar
present
blue to green mixture trace amount
blue to yellow / orange
precipitate
moderate amount
blue to brick-red
precipitate
large amount

29. Food Test (2)Food Test (2)
Test for Reducing Sugars – Benedict’sTest for Reducing Sugars – Benedict’s
TestTest
Results
Positive Benedict’s test Negative Benedict’s test
Brick Red
Precipitate
Blue
solution

30. Topic 3: Chapter 4
NutrientsNutrients –– Part 2Part 2
FatFat
ss

31. LipidsLipids
SteroidsSteroids
ExamplesExamples
PhospholipidsPhospholipidsFatsFats
For storage
of energy
For storage
of energy
e.g. cholesterole.g. cholesterol
Makes up the
Plasma
membrane
Makes up the
Plasma
membrane

32. A(2): FATS
• Organic compounds made up of the
elements carbon (C), hydrogen (H) & oxygen
(O).
• but unlike carbohydrates, they contain much
less oxygen in proportion to hydrogen. (E.g.
Beef Fat: Tristearin – C57H110O6)
• No General formula for fats

33. A(2): Composition of a Fat
Molecule
• A fat molecule is made up of four parts:
- 1 molecule of glycerol
- 3 fatty acid chains
Glycerol
Fatty
Acids

34. A(2): Breaking down fats
Hydrolysi
s
Hydrolysi
s
• The breaking down of 1 fat molecule involves the
addition of 3 water molecules to form 1 glycerol and
3 fatty acid molecules IN THE PRESENCE OF AN
ENZYME (Lipase)

35. A(2): Forming fats
Condensatio
n
Condensatio
n
• Conversely, a fat molecule can be formed by
adding 3 fatty acid molecules to 1 glycerol
molecule, removing 3 molecules of water

36. A(2): Groups of Fats
FatsFats
Unsaturated FatsUnsaturated FatsSaturated FatsSaturated Fats

37. A(2):
• Found mostly in animals
• Fatty acids are straight
chains
• Most are solid at room
temperature (e.g butter)
• Cholesterol usually found
with polysaturated fats 
Increases risk of Coronary
Heart Diseases & Gall stone
formation
Saturated FatsSaturated Fats

38. • Found mostly in vegetables
(except Coconut and Palm Oil)
• Fatty acids are bent in some
places
• Most are liquid at room
temperature (e.g Olive Oil)
• Fatty acid chains contains double
bonds and are able to take in 1 or
more pairs of H-atoms
• Hydrogenation of unsaturated
fats  Trans-fat
A(1): Unsaturated FatsUnsaturated Fats

39. Saturated Fats Unsaturated Fats
 Butter
 Cheese
 Fatty Meats
 Coconut oil
 Palm oil
 Peanuts
 Walnuts
 Olives
 Corn Oil
 Soybean
 Most fishes (e.g Salmon,
mackerel, tuna, sardines)
A(2): Sources of Fats

40. A(1): Functions Fats
a) as a source and store of energy
b) Insulating material (Prevents excessive heat
loss)
 e.g layer of blubber beneath the skin of whales
a) Solvent for fat-soluble substances
 some vitamins and vital substances (e.g hormones)
d) Essential part of the protoplasm
 e.g cell membrane (Phospholipds and cholesterol)
e) A way to reduce water loss from the skin
surface

41. Food Test (3)Food Test (3)
Test for Fats – Alcohol EmulsionTest for Fats – Alcohol Emulsion
TestTest
Procedure:
 Add 2 cm3
of ethanol to the test solution and
shake the mixture thoroughly for 5 minutes.
Observe for changes.
 Add 2 cm3
of water to the mixture and shake
the mixture. Observe for changes.
Liquid Food

42. Food Test (3)Food Test (3)
Test for Fats – Alcohol EmulsionTest for Fats – Alcohol Emulsion
TestTest
Procedure:
 Cut the sample into small pieces and place
them in a test tube.
 Add 2cm3
of ethanol and shake thoroughly.
 Allow the solid particles to settle. Decant the
ethanol into another test tube containing 2cm3
of water. Make observations.
Solid Food

43. Food Test (3)Food Test (3)
Test for Fats – Alcohol EmulsionTest for Fats – Alcohol Emulsion
TestTest
Results:
 A white emulsion is formed if fats is present
white
emulsio
n

44. Topic 3: Chapter 4
NutrientsNutrients –– Part 3Part 3
ProteiProtei
nsns

45. Where are Proteins found in
our body?

46. A(3): Proteins
• Are very large complex organic moluecules
containing carbon (C), hydrogen (H), oxygen
(O) and nitrogen (N). Sometimes, Sulfur (S)
and Phosphorus (P)
• E.g. Insulin: C254H317O75N65S6
• Made up of basic small units called amino
acids

47. ProteinsProteins
Acidic Group
-COOH
Acidic Group
-COOH
Formed
from
Formed
from
R-Groups:
May contain:
Sulphur,
Acidic groups,
amino groups, and/or
Hydroxyl groups
R-Groups:
May contain:
Sulphur,
Acidic groups,
amino groups, and/or
Hydroxyl groups
Amino Group
-NH2
Amino Group
-NH2
Amino Acids
NH2-CHR-COOH
Amino Acids
NH2-CHR-COOH

48. A(3): General Structure of an
amino acid
• A fat molecule is made up of four parts:
- 1 Amino Acid group (-NH2)
- 1 Acidic Group (-COOH)
- 1 Side Chain (denoted by R)
Can be:
•Sulfur (S)
•Acidic groups (-COOH)
•Amino groups (--NH2)
and/or
•Hydroxyl groups (-OH)

49. A(3): Why is there a need for so
many different R-groups?
• The R-Group determines the type of
amino acid formed.
• There are 20 naturally occuring amino acid:
• Examples –
• Leucine, Valine, Glutamine:
• 8 Essential a.a: Cannot be synthesized by the
body. Must be obtained through the diet
• 12 Non-Essential a.a: Can be synthesized by
the body

50. A(3): Synthesis of Proteins
• The bond between 2 amino acids is called: Peptide Bond
• Many amino acids link together by peptide bonds to form a
polypeptide chain / peptone
Condensatio
n
Condensatio
n

51. amino acids polypeptides Protein molecule
A(3): Synthesis of Proteins
Primary / Secondary
Structure
Primary / Secondary
Structure
Tertiary
Structure
Tertiary
Structure
Amino acids are
linked by
peptide bonds
to form
polypeptide
chains
Amino acids are
linked by
peptide bonds
to form
polypeptide
chains
Polypeptide
chains coil and
fold around each
other to form a
3-d structure
held by weak
H-bonds
Polypeptide
chains coil and
fold around each
other to form a
3-d structure
held by weak
H-bonds

52. Different proteins have a different
sequence of A.A
 A.A sequence determines the
bonds formed and the structure of
the protein.
 Different proteins with different
structures perform different
functions.
Weak H-bonds can be easily
broken by:
• Heat
• Chemicals like Acid and Alkalis
Protein loses its structure
and function (is
DENATURED)
Different proteins have a different
sequence of A.A
 A.A sequence determines the
bonds formed and the structure of
the protein.
 Different proteins with different
structures perform different
functions.
Weak H-bonds can be easily
broken by:
• Heat
• Chemicals like Acid and Alkalis
Protein loses its structure
and function (is
DENATURED)
Structure VS FunctionStructure VS Function

53. A(3): Digestion of Proteins
polypeptides
amino acids
protein
hydrolysis (digestion)
hydrolysis (digestion)
Protein molecules are too
large to pass through the cell
membranes
Smaller and simpler A.A
molecules are soluble in
water and can pass
through the cell membrane
into the cells to synthesize
new proteins

54. Animals Plants
 Milk
 Eggs
 Seafood
 Chicken
 Lean beef
 Nuts
 Soy bean
 Grains
 Vegetables
A(3): Sources of Proteins

55. A(1): Functions Proteins
a) Formation of new protoplasm
 for growth & repair of worn-out body parts/ cells
b) Synthesis of enzymes and hormones
 e.g digestive enzymes and insulin / sex and
growth hormones
b) Formation of antibodies to combat diseases
d) Can be source of energy

56. Food Test (4)Food Test (4)
Test for Proteins – Biuret TestTest for Proteins – Biuret Test
Procedure:
 Add 1 cm3
of sodium hydroxide solution to the
2 cm3
of test solution. Shake thoroughly.
 Add 1% copper (II) sulphate solution, drop by
drop, shaking after each drop.
ALTERNATIVELY
 Add 2cm3
of test solution to an equal volume
of Biuret solution. Shake well and allow the
mixture to stand for 5 minutes.

57. Food Test (4)Food Test (4)
Test for Proteins – Biuret TestTest for Proteins – Biuret Test
Results:
 A violet colouration is
formed if proteins is
present
positive test
for protein
positive test
for protein