1.3.1 Function of Food Why do we need food?

Food is needed for: 1.Energy 2.Growth of new cells and Repair of existing cells, tissues, organs, etc. 2

Food also supplies: the materials and energy for the processes of: Metabolism 3

Learning check Why do we need food? Energy Growth of new cells and Repair of existing cells, tissues, organs, etc. What is metabolism? Metabolism is the chemical reactions that occur in the cells of living organisms What is continuity? Continuity of life is the ability of an organism to exist from generation to the next 4

1.3.2 Chemical Elements Elements in Food

What is Food made up of? Food is made up of: Six chemical elements C, H, O, N, P, S Salts of Na, Mg, Cl, K, Ca Three trace elements Fe, Cu, Zn 6

Chemical Elements and their Symbols CalciumCaNitrogenN CarbonCOxygenO ChlorineClPhosphorusP CopperCuPotassiumK HydrogenHSodiumNa IronFeSulphurS MagnesiumMgZincZn 7

Types of Food The elements combine in different ratios to form different food components (biomolecules) Food is made up of six different components WaterProteins Lipids Carbohydrates Vitamins Minerals 8

Learning check What are the six different food components? WaterProteins Lipids Carbohydrates Vitamins Minerals 9

Food Food is any substance used by living organisms to provide energy, materials for repair and maintenance or to control metabolism

Humans are mainly made up of Water! 11

Biomolecules Biomolecules are complex molecules made up of different elements. There are 4 main types of bio-molecules: Carbohydrates Lipids Proteins Vitamins

Carbohydrates Carbohydrates contain the elements CarbonHydrogenOxygen The general formula for a carbohydrate is C x (H 2 O) y Ratio Hydrogen:Oxygen 2: 1 13

A common carbohydrate General formula = C x (H 2 O) y When x = y = 6 We get the formula C 6 H 12 O 6 What is the name of this monosaccharide carbohydrate? Glucose 14

Learning check Name the three elements that make up carbohydrates CarbonHydrogenOxygen What is the general formula for a carbohydrate? C x (H 2 O) y 15

Carbohydrates Carbohydrates contain the elements Carbon Hydrogen Oxygen Usually in the ratio of 1C:2H:1O They have twice as many hydrogen molecules as oxygen molecules 16

3 Types of Carbohydrate Monosaccharides Disaccharides Polysaccharides 17

Monosaccharides These are single sugar molecules simple sugars soluble in water sweet to taste smallest carbohydrate unit Examples:glucose, fructose Found in:fruit 18 O CC C C C C

Disaccharides These are two monosaccharide sugar units joined together – known as double sugar molecules soluble in water sweet to taste Examples: sucrose, lactose, maltose Found in:table sugar, milk 19

Polysaccharides These are Many monosaccharide sugar molecules joined together Not soluble in water Do not taste sweet Example:starch, cellulose Found in:bread, pasta, cereals 20

Learning check Name the three types of carbohydrate Monosaccharides Disaccharides Polysaccharides 21

Lipids Lipids are a diverse group of substances which include fats (solid at room temp.) oils (liquid at room temp.) 22

Structure of Lipids They are made up of the elements carbon hydrogen oxygen But not have the same ratios as carbohydrates. They are made up of two main types of molecules Fatty acids and Glycerol 23

Learning check Give examples and sources of: 24 ExamplesSources Monosaccharides Disaccharides Polysaccharides Glucose Fructose fruit Sucrose Lactose Table sugar Milk Starch Cellulose Bread, Pasta, Cereals

Types of Lipid Two of the main types of lipids are Triglycerides Phospholipids 25

Triglyceride It is made up of 3 fatty acid molecules and 1 glycerol molecule 26 This is the smallest lipid

Phospholipids If one fatty acid of a lipid molecule is replaced by a phosphate group then a phospholipid is formed 27

Sources of Lipids Fat – in and on meat Butter (80% fat) Cooking oils 28

Learning check The two main types of molecules that make up lipids are: Fatty acids and Glycerol The two main types of lipids are: Triglycerides Phospholipids 29

Proteins Proteins contain the elements Carbon Hydrogen Oxygen Nitrogen Some may also contain sulphur, phosphorous or iron Proteins are found in lean meat, fish, pulses, soya and eggs 30

Structure of Proteins Proteins are made up of long chains of amino acids Amino acids are joined together by peptide bonds This results in the formation of polypeptide chains 31

Learning check Name the elements in proteins Carbon Hydrogen Oxygen Nitrogen Sometimes they contain sulphur, phosphorous or iron Proteins are made up of long chains of amino acids 32

Need to know What is a vitamin? Name one water soluble vitamin. Name one water in-soluble vitamin (fat- soluble) List the sources of these vitamins 33

Vitamins Vitamins are complex organic chemicals that must be taken in the diet. Needed in small amounts, cannot be produced in the body Must be supplied continuously in diet and in sufficient quantities 34

Vitamins We need Vitamins A, B, C, D, E and K in our diets to keep us healthy Vitamins can be water soluble or fat soluble Vitamins B and C are water soluble Vitamins A, D, E and K are fat soluble 35

Sources of Vitamins VitaminSource A Green leafy vegetables, Eggs, Cheese, Carrots B Lean Meat, Cereals, Nuts C Citrus Fruits, Green vegetables, Turnips D Milk and Milk products, Sunlight E Vegetable oils, fish, nuts K Green leafy vegetables 36

Learning check What is a vitamin? A vitamin is a complex organic chemical that must be taken in the diet. What vitamins dissolve in water? B & C What vitamins are fat-soluble? A, D, E and K 37

Minerals Minerals are inorganic chemicals necessary in tiny amounts in the diet.

Plant MineralSourceFunctionDeficiency PhosphateSoilPart of nucleic acids Poor root growth MagnesiumSoilPart of chlorophyll Lack of chlorophyll Animal Minerals IronLiver, meatPart of haemoglobin Low red blood cell count CalciumMilk cheeseBonesWeak bones

To Test for Reducing Sugars Procedure (pg 2 & 77) 1.Label test tubes A-F 2.Place 2cm glucose solution in test tube A 3.Place 2cm water (control) in test tube B 4.Place 2cm of each of the other foods in C-F 5.Add 2cm Benedicts Solution to each test tube. 6. Place test tubes in a water bath for 5- 10min 40

To test for Reducing Sugars pg. 2 & Swirl the test tubes and note any colour change. 8. Record your results in the table. Colour Change after heating test tube Blue -> brick red means reducing sugar present 41

To Test Food Samples for Starch pg. 4 & 78 Procedure 1.Label the wells in a spotting tile A-F 2.Add 1cm starch solution to well A 3.Add 1cm water (control) to well B 4.Add 1cm iodine solution to each well 5.Add 1cm other foods to well C-F and 1cm iodine solution 6.Record results in table 42

To test foods for Starch Colour Change Iodine solution should turn blue/black in colour if starch is present in the food. 43

To test a variety of foods for Fat Procedure (pg 6 & 79) 1.Label six pieces of brown paper A-F 2.Place one drop of oil on A and leave to dry. 3.Place one drop of water on B and leave to dry. 4.Repeat steps 2 with other food samples 5.Record results when brown paper dries. 44

To test a variety of foods for Fat A translucent spot (see through spot) from the food sample will be visible on the dry brown paper if fat is present in the food 45

To Test a variety of foods for Protein using Biuret Test Procedure (pg 8 & 80) 1.Label spotting tile A-F 2.Place 1cm milk in well A 3.Add 1cm water (control) to well B 4.Add 1cm of Sodium hydroxide to well A and 2 drops of Copper sulphate. 5.Observe result 6.Repeat step 4-5 for other foods. 46

To test a variety of foods for protein using the Biuret Test The blue solution will turn purple/lilac if protein is present in the food. 47

Results Table FoodColour ChangePresence/Absence A. B. C. D. E. F G. 48