Functions of FoodFunctions of Food
• to maintain life
• to supply energy & give warmth
– carbohydrates
– fats
– proteins
•...
• elements : C, H, O
– ratio of H : O
= 2 : 1
• monosaccharides
– C6H12O6
– all are sweet & soluble in water
– all are Red...
disaccharides (from 2 monosaccharides)
– C12H22O11
– all are sweet & soluble in water
– Maltose ( 2 glucose molecules )
– ...
CarbohydratesCarbohydrates
• polysaccharides (NOT sugar)
• for energy storage
– starch (store in plants)
glycogen (store i...
main source of energy
cellulose:
- fibrous material of Plant Cell Wall
- dietary fibre: stimulates Peristalsis
excess carb...
Test for Reducing Sugars
(Benedict’s Test)
Is there any colour change in
tubes A and B ?
Ans: Only the mixture in tube
A has a colour change.
A B
glucose
solution +
...
What is the sequence of
change when there is a colour
change ?
Ans: The blue solution changes
first to green, then to a
ye...
Test for Starch
(Iodine Test)
What is the final colour in
tube A ?
Ans: The solution in tube A
changes from brown
to blue black.
iodine solution
starch
...
What is the purpose of
setting up tube B ?
Ans: To act as a control.
iodine solution
starch
solution
distilled
water
A B
ProteinsProteins
• elements: C, H, O, N,
sometimes S, P
• components : amino acids
forms dipeptides & polypeptides
• Conde...
Proteins
• are compounds of carbon, hydrogen, oxygen,
nitrogen and sometimes sulphur, phosphorus
• amino acids:
– unit of ...
An amino acid molecules
H2N
amino group
COOH
carboxyl group
C
R
H
The condensation and hydrolysis of a
polypeptide
5
1 4
3
2
1 2 3 4 5
hydrolysiscondensation
Condensation of two amino acid to form a
dipeptide
H2N C
R1
H
C
O
OH H
N
H
C
H
R2
COOH
H2N C
R1
H
O
H
C
H
R2
COOHC---N
H2O
cannot be stored
- excess proteins are deaminated by liver
~ to Urea which will be excreted away by
Kidney
~ to Carbohydra...
Functions of ProteinsFunctions of Proteins
• for growth and repair of body cells
(as structural components (cell
membrane ...
Deficiency disease of proteins
Kwashiorkor
Test for Proteins
(Biuret Test)
Test for proteins / Biuret test
egg white solution
1 cm3
NaOH solution
Put CuSO2 solution drop by
drop, and shake the mixt...
What colour changes in
tubes A and B ?
Ans: Mixture in tube A
changes from blue
to purple while
mixture in tube B
remains ...
Lipids ( fats & oils )Lipids ( fats & oils )
• elements : C, H, O
• components of 1 lipid molecule:
1 glycerol + 3 fatty a...
Functions of LipidsFunctions of Lipids
give energy
component of cell membrane
form fatty tissues under skin
> to store ene...
Spot Test for Fat
Which substance, oil or water,
leaves a permanent
translucent spot on the filter
paper ?
Ans: Oil.
Emulsion Test for Fat
Which test tube has an emulsion formed ?
Ans: Test tube A.
2 drops of
cooking oil
2 cm3
of
alcohol
2 cm3
of
distilled
wate...
What happens to the other tube ?
Ans: The mixture separates into two layers because
fats do not dissolve in water.
2 drops...
VitaminsVitamins
• no energy value
• essential for small amount to
maintain good health
• water soluble vitamins
( B, C )
...
Vitamin AVitamin A
 formed in the body from Carrotene
(a yellow pigment in carrots)
 destroyed at high temperature
esse...
Vitamin CVitamin C
 Destroyed after prolonged cooking
 Necessary for wounds-healing
Vitamin DVitamin D
 Formed in Skin ...
Detection of Vitamin C in Lemon
Juice by using DCPIP
What colour change has
occurred ?
Ans: The blue DCPIP
decolourizes.
syringe
lemon juice
DCPIP solution
What conclusion can you draw ?
Ans: Lemon juice contains
vitamin C which
decolourizes blue DCPIP.
syringe
lemon juice
DCPI...
Vitamin Sources
Deficiency
Disease
A
Egg yolk, milk,
cheese, carrot,
green
vegetables
Night blindness
C
Fresh fruits &
gre...
Food TestsFood Tests
Substances Test
Original
Colour
Positive Result
Reducing
Sugar
Benedict’s Blue Orange ppt
Starch Iodi...
Mineral SaltsMineral Salts
regulate body metabolism
essential for healthy growth
necessary for construction of certain
tis...
Mineral(s) Sources Functions
Deficiency
Disease
Calcium &
Phosphorus
Cheese,
milk,
vegetables
Making bones &
teeth
Importa...
Dietary FibreDietary Fibre
mainly cellulose
indigestible material for human
give bulk to food & stimulate peristalsis 
pr...
Balanced DietBalanced Diet
• have enough food to supply enough
– energy
• carbohydrates, fats, proteins
– body building ma...
Energy Contents in FoodEnergy Contents in Food
• Calorimeter is used to measure the
amount of energy contained in a
partic...
Factors affecting energyFactors affecting energy
requirementrequirement
• Sex
• Age
• Occupation
• Physical Activities
• S...
Measure the Energy
Value of Food
boiling tube
water
burning
peanut
thermometer
Explain why the energy value
of the peanut is lower than
those from standard...
Basal Metabolic Rate (BMR)Basal Metabolic Rate (BMR)
minimum amount of energy needed by an
individual lying awake in bed t...
~~ ENDEND ~~
05 food requirements_in_human
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05 food requirements_in_human

  1. 1. Functions of FoodFunctions of Food • to maintain life • to supply energy & give warmth – carbohydrates – fats – proteins • for growth and repair – Proteins • keep healthy & help to fight against disease
  2. 2. • elements : C, H, O – ratio of H : O = 2 : 1 • monosaccharides – C6H12O6 – all are sweet & soluble in water – all are Reducing Sugars – include Glucose, Fructose & Galactose CarbohydratesCarbohydrates
  3. 3. disaccharides (from 2 monosaccharides) – C12H22O11 – all are sweet & soluble in water – Maltose ( 2 glucose molecules ) – Sucrose ( glucose + fructose) (non-reducing sugar) – Lactose ( glucose + galactose) CarbohydratesCarbohydrates surcosesurcose
  4. 4. CarbohydratesCarbohydrates • polysaccharides (NOT sugar) • for energy storage – starch (store in plants) glycogen (store in animals) • Hydrolysis: Polysaccharide +H2O  Disaccharides +H2O  Monosaccharides
  5. 5. main source of energy cellulose: - fibrous material of Plant Cell Wall - dietary fibre: stimulates Peristalsis excess carbohydrates - stored as glycogen in liver & muscle - stored as fats under skin Functions of CarbohydratesFunctions of Carbohydrates
  6. 6. Test for Reducing Sugars (Benedict’s Test)
  7. 7. Is there any colour change in tubes A and B ? Ans: Only the mixture in tube A has a colour change. A B glucose solution + Benedict’s solution distilled water + Benedict’s solution water bath
  8. 8. What is the sequence of change when there is a colour change ? Ans: The blue solution changes first to green, then to a yellow coloration and eventually a brick-red precipitate is produced. A B glucose solution + Benedict’s solution distilled water + Benedict’s solution water bath
  9. 9. Test for Starch (Iodine Test)
  10. 10. What is the final colour in tube A ? Ans: The solution in tube A changes from brown to blue black. iodine solution starch solution distilled water A B
  11. 11. What is the purpose of setting up tube B ? Ans: To act as a control. iodine solution starch solution distilled water A B
  12. 12. ProteinsProteins • elements: C, H, O, N, sometimes S, P • components : amino acids forms dipeptides & polypeptides • Condensation: Amino acids –H2O  Dipeptides –H2O  Polypeptide
  13. 13. Proteins • are compounds of carbon, hydrogen, oxygen, nitrogen and sometimes sulphur, phosphorus • amino acids: – unit of proteins – about 20 different types – essential and non-essential types
  14. 14. An amino acid molecules H2N amino group COOH carboxyl group C R H
  15. 15. The condensation and hydrolysis of a polypeptide 5 1 4 3 2 1 2 3 4 5 hydrolysiscondensation
  16. 16. Condensation of two amino acid to form a dipeptide H2N C R1 H C O OH H N H C H R2 COOH H2N C R1 H O H C H R2 COOHC---N H2O
  17. 17. cannot be stored - excess proteins are deaminated by liver ~ to Urea which will be excreted away by Kidney ~ to Carbohydrates (Glycogen) which will be stored in Liver ProteinsProteins
  18. 18. Functions of ProteinsFunctions of Proteins • for growth and repair of body cells (as structural components (cell membrane and cytoplasm) of cells) • to produce hormones and enzymes and antibodies • to give energy • for making Haemoglobin in blood • for making Antibodies
  19. 19. Deficiency disease of proteins Kwashiorkor
  20. 20. Test for Proteins (Biuret Test)
  21. 21. Test for proteins / Biuret test egg white solution 1 cm3 NaOH solution Put CuSO2 solution drop by drop, and shake the mixture after addition of each drop Positive result: purple colour
  22. 22. What colour changes in tubes A and B ? Ans: Mixture in tube A changes from blue to purple while mixture in tube B remains blue without any change. copper sulphate solution egg white + sodium hydroxide solution water + sodium hydroxide solution A B
  23. 23. Lipids ( fats & oils )Lipids ( fats & oils ) • elements : C, H, O • components of 1 lipid molecule: 1 glycerol + 3 fatty acids • insoluble in water • soluble in organic solvent
  24. 24. Functions of LipidsFunctions of Lipids give energy component of cell membrane form fatty tissues under skin > to store energy > acts as insulator to keep warm to transport fat-soluble vitamins (A, D, E, K)
  25. 25. Spot Test for Fat
  26. 26. Which substance, oil or water, leaves a permanent translucent spot on the filter paper ? Ans: Oil.
  27. 27. Emulsion Test for Fat
  28. 28. Which test tube has an emulsion formed ? Ans: Test tube A. 2 drops of cooking oil 2 cm3 of alcohol 2 cm3 of distilled water after shaking to form a clear solution shake and then allow to stand emulsion oil water shake and then allow to stand shaking 2 drops of cooking oil 2 cm3 of distilled water 2 cm3 of distilled water A B
  29. 29. What happens to the other tube ? Ans: The mixture separates into two layers because fats do not dissolve in water. 2 drops of cooking oil 2 cm3 of alcohol 2 cm3 of distilled water after shaking to form a clear solution shake and then allow to stand emulsion oil water shake and then allow to stand shaking 2 drops of cooking oil 2 cm3 of distilled water 2 cm3 of distilled water A B
  30. 30. VitaminsVitamins • no energy value • essential for small amount to maintain good health • water soluble vitamins ( B, C ) • fat soluble vitamins ( A, D, E, K ) excessive of some vitamins may be harmful
  31. 31. Vitamin AVitamin A  formed in the body from Carrotene (a yellow pigment in carrots)  destroyed at high temperature essential for forming visual purple (maintain dim light vision)
  32. 32. Vitamin CVitamin C  Destroyed after prolonged cooking  Necessary for wounds-healing Vitamin DVitamin D  Formed in Skin from Ultraviolet Light  Help to regulate Ca & P metabolism
  33. 33. Detection of Vitamin C in Lemon Juice by using DCPIP
  34. 34. What colour change has occurred ? Ans: The blue DCPIP decolourizes. syringe lemon juice DCPIP solution
  35. 35. What conclusion can you draw ? Ans: Lemon juice contains vitamin C which decolourizes blue DCPIP. syringe lemon juice DCPIP solution
  36. 36. Vitamin Sources Deficiency Disease A Egg yolk, milk, cheese, carrot, green vegetables Night blindness C Fresh fruits & green vegetables Scurvy D Cod liver oil & egg yolk Rickets
  37. 37. Food TestsFood Tests Substances Test Original Colour Positive Result Reducing Sugar Benedict’s Blue Orange ppt Starch Iodine Brown Blue-black Protein Biuret Blue Violet Fats/Oils Spot --- Translucent spot Fats/Oils Emulsion Clear Milky emulsion Vitamin C DCPIP Blue Colourless (decolourize)
  38. 38. Mineral SaltsMineral Salts regulate body metabolism essential for healthy growth necessary for construction of certain tissues needed in small amount include Ca, S, K, Na, Mg, Fe, I
  39. 39. Mineral(s) Sources Functions Deficiency Disease Calcium & Phosphorus Cheese, milk, vegetables Making bones & teeth Important for blood clotting & muscle contraction Rickets Iron Liver, eggs, beef, green leafy vegetables Structural component of Haemoglobin Anaemia
  40. 40. Dietary FibreDietary Fibre mainly cellulose indigestible material for human give bulk to food & stimulate peristalsis  prevent Constipation lack of dietary fibre: Large Intestine Cancer sources: wholemeal cereals, unpolished rice, fresh vegetables & fruits
  41. 41. Balanced DietBalanced Diet • have enough food to supply enough – energy • carbohydrates, fats, proteins – body building materials • proteins – substances to maintain health • vitamins, minerals, water & dietary fibres • malnutrition : not having balanced diets for long time
  42. 42. Energy Contents in FoodEnergy Contents in Food • Calorimeter is used to measure the amount of energy contained in a particular type of food • Carbohydrate (17kJ/g) • Protein (18kJ/g) • Fat (39kJ/g)
  43. 43. Factors affecting energyFactors affecting energy requirementrequirement • Sex • Age • Occupation • Physical Activities • Stage of individual (pregnancy, breast-feeding)
  44. 44. Measure the Energy Value of Food
  45. 45. boiling tube water burning peanut thermometer Explain why the energy value of the peanut is lower than those from standard tables. Ans: Because there are a number of inaccuracies associated with this method due to incomplete combustion and heat loss.
  46. 46. Basal Metabolic Rate (BMR)Basal Metabolic Rate (BMR) minimum amount of energy needed by an individual lying awake in bed to maintain breathing, body temperature & heartbeat varies from one individual to another daily energy requirement > basal metabolic rate
  47. 47. ~~ ENDEND ~~

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