to maintain life to supply energy & give warmth
◦ carbohydrates◦ fats◦ proteins
for growth and repair◦ Proteins
keep healthy & help to fight against disease
Functions of Food
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
Carbohydrates
disaccharides (from 2 monosaccharides) – C12H22O11
– all are sweet & soluble in water– Maltose ( 2 glucose molecules )– Sucrose ( glucose + fructose)
(non-reducing sugar)– Lactose ( glucose + galactose)
Carbohydrates
surcose
polysaccharides (NOT sugar) for energy storage
◦starch (store in plants)glycogen (store in animals)
Hydrolysis: Polysaccharide +H2O
Disaccharides +H2O Monosaccharides
Carbohydrates
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 Carbohydrates
Is there any colour change in tubes A and B ?Ans: Only the mixture
in tube A has a colour change.
A Bglucose solution
+ Benedict
’s solution
distilled water +
Benedict’s solution
water bath
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 Bglucose solution
+ Benedict
’s solution
distilled water +
Benedict’s solution
water bath
What is the final colour in tube A ?
Ans: The solution in tube A changes from brown to blue black.
iodine solution
starch solutio
n
distilled water
A B
What is the purpose of setting up tube B ?Ans: To act as a
control.
iodine solution
starch solutio
n
distilled water
A B
elements: C, H, O, N, sometimes S, P
components : amino acidsforms dipeptides & polypeptides
Condensation: Amino acids –H2O Dipeptides –H2O Polypeptide
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
Proteins
Condensation of two amino acid to form a dipeptide
H2N C
R1
H
C
O
OH HN
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 Carbohydrates (Glycogen) which will be stored in Liver
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
Functions of Proteins
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
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
elements : C, H, O components of 1 lipid molecule: 1 glycerol + 3 fatty acids insoluble in water soluble in organic solvent
Lipids ( fats & oils )
Functions 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)
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
oilwater
shake and then allow to
stand
shaking
2 drops of
cooking oil
2 cm3 of distilled water
2 cm3 of distilled water
A
B
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
oilwater
shake and then allow to
stand
shaking
2 drops of
cooking oil
2 cm3 of distilled water
2 cm3 of distilled water
A
B
no energy value essential for small amount
to maintain good health water soluble vitamins
( B, C ) fat soluble vitamins
( A, D, E, K )
Vitamins
excessive of some vitamins may be harmful
Vitamin 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)
Vitamin C Destroyed after prolonged cooking
Necessary for wounds-healing
Vitamin D Formed in Skin from Ultraviolet Light Help to regulate Ca & P metabolism
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
DCPIP solution
Vitamin Sources Deficiency Disease
A
Egg yolk, milk, cheese, carrot, green vegetables
Night blindness
CFresh fruits &
green vegetables
Scurvy
DCod liver oil & egg yolk
Rickets
Food TestsSubstance
sTest
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 ClearMilky
emulsion
Vitamin C DCPIP BlueColourless
(decolourize)
Mineral 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
Mineral(s) Sources FunctionsDeficiency
Disease
Calcium & Phosphor
us
Cheese, milk, vegetables
Making bones & teethImportant for blood clotting & muscle contraction
Rickets
Iron
Liver, eggs, beef, green leafy vegetables
Structural component of Haemoglobin
Anaemia
Dietary 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
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
Balanced Diet
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)
Energy Contents in Food
Sex Age Occupation Physical Activities Stage of individual
(pregnancy, breast-feeding)
Factors affecting energy requirement
boiling tubewater
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.
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