Functions 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

Carbohydrates 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 surcose Maltose ( 2 glucose molecules ) Sucrose ( glucose + fructose) (non-reducing sugar) Lactose ( glucose + galactose)

Carbohydrates polysaccharides (NOT sugar) for energy storage starch (store in plants) glycogen (store in animals) Hydrolysis: Polysaccharide +H2O  Disaccharides +H2O  Monosaccharides

Functions of 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

Test for Reducing Sugars (Benedict’s Test) Investigation 5.1 Test for Reducing Sugars (Benedict’s Test)

Is there any colour change in tubes A and B ? glucose solution + Benedict’s solution distilled water + Benedict’s solution water bath Is there any colour change in tubes A and B ? Ans: Only the mixture in tube A has a colour change.

What is the sequence of change when there is a colour change ? B glucose 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.

Test for Starch (Iodine Test) Investigation 5.2 Test for Starch (Iodine Test)

What is the final colour in tube A ? iodine solution starch solution distilled water A B What is the final colour in tube A ? Ans: The solution in tube A changes from brown to blue black.

What is the purpose of setting up tube B ? iodine solution starch solution distilled water A B What is the purpose of setting up tube B ? Ans: To act as a control.

Proteins elements: C, H, O, N, sometimes S, P components : amino acids forms 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

An amino acid molecules R C COOH carboxyl group H2N amino group H

The condensation and hydrolysis of a polypeptide 4 1 2 5 3 condensation hydrolysis 1 2 3 4 5

Condensation of two amino acid to form a dipeptide H H C H2N C N C COOH OH H H R2 H2O R1 H O C H2N C---N C COOH H H R2

Proteins 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

Functions 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

Deficiency disease of proteins Kwashiorkor

Test for Proteins (Biuret Test) Investigation 5.3 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 mixture after addition of each drop Positive result: purple colour

What colour changes in tubes A and B ? copper sulphate solution egg white + sodium hydroxide solution water + sodium hydroxide solution A B 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.

Lipids ( fats & oils ) elements : C, H, O components of 1 lipid molecule: 1 glycerol + 3 fatty acids insoluble in water soluble in organic solvent

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)

Investigation 5.4 Spot Test for Fat

Which substance, oil or water, leaves a permanent translucent spot on the filter paper ? Ans: Oil.

Investigation 5.5 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 water after shaking to form a clear solution shake and then allow to stand emulsion oil water shaking A B Which test tube has an emulsion formed ? Ans: Test tube A.

What happens to the other tube ? 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 shaking A B What happens to the other tube ? Ans: The mixture separates into two layers because fats do not dissolve in water.

Vitamins 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

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 Vitamin D Destroyed after prolonged cooking Necessary for wounds-healing Vitamin D Formed in Skin from Ultraviolet Light Help to regulate Ca & P metabolism

Detection of Vitamin C in Lemon Juice by using DCPIP Investigation 5.6 Detection of Vitamin C in Lemon Juice by using DCPIP

What colour change has occurred ? syringe lemon juice DCPIP solution What colour change has occurred ? Ans: The blue DCPIP decolourizes.

What conclusion can you draw ? syringe lemon juice DCPIP solution What conclusion can you draw ? Ans: Lemon juice contains vitamin C which decolourizes blue DCPIP.

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

Colourless (decolourize) Food Tests Substances Test Original Colour Positive Result Reducing Sugar Benedict’s Blue Orange ppt Starch Iodine Brown Blue-black Protein Biuret Violet Fats/Oils Spot --- Translucent spot Emulsion Clear Milky emulsion Vitamin C DCPIP Colourless (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 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

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

Balanced 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

Energy 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)

Factors affecting energy requirement Sex Age Occupation Physical Activities Stage of individual (pregnancy, breast-feeding)

Measure the Energy Value of Food Investigation 5.8 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 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

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