Chapter 5 - Nutrition (food)

Chapte r 5

Food 1

Contents You will learn... 

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the chemical elements that make up carbohydrates, fats and proteins. tests for starch, reducing sugar, proteins and fats. the sources of carbohydrates, fats, proteins, fibre, vitamins, mineral salts and water. the dietary importance of the seven classes of nutrients. the deficiency symptoms for vitamins and mineral salts. 2

Nutrients Importance of Nutrients Carbohydrates, proteins, fats, vitamins and minerals are essential nutrients that are needed by the body for   

Growth Repair Maintenance

Nutrients in canned foods are listed on labels

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s Sugars fruits, vegetables and milk

Sugars: Either monosaccharides (simple sugars) Carbohydrate: Compound composed of carbon, hydrogen and oxygen in the ratio of 1:2:1

disaccharides (complex sugars).

polysaccharides Eg. Starch (C6H10O5)n

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Carbohydrates

Test for reducing sugar

Add a small amount of Benedict’s solution to the sample. Boil the mixture Benedict’s solution remains clear blue sugar is absent.

The presence of sugar is indicated by the formation of a precipitate from green, through to yellow and orange, to brick red.

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Carbohydrates

Iodine test for starch

This starch test is performed by adding a few drops iodine solution to the sample.

Starch present

Starch absent

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Fats are compounds that contain carbon, hydrogen and oxygen.

Different kinds of fats  different fatty acids attached to glycerol.

Fats

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Fats

Oils fats which are liquid at room temperature. Waxes  fats which are solid at room temperature. 8

Fats • Fats provide more than twice the energy as carbohydrates • Excess food is stored as fats under the skin and around organs • The layer of fats beneath the skin serves as an insulating layer • It helps to protect organs from physical injuries • Stored fat is used as a reserve supply of energy • Fats act as a medium for the intake of fat-soluble vitamins such as vitamins A, D, E and K

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Fats

Types of Fats

Unsaturated fatty acid  contains < max amount of H possible. Very unsaturated fatty acids  polyunsaturates.

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Fats Types of Fats

• Fats that are solid at room temperature tend to be high in saturated fats.

Healthy artery

• Saturated fats increase the level of cholesterol in the blood. • Diets rich in cholesterol and saturated fats increases the risk of heart disease.

Damaged artery 11

Fats

Emulsion test for fats Dissolve the sample liquid in ethanol. Water is then added to the mixture. Emulsion formed  Fat is present.

water

one drop of sample

2cm3 of ethanol 12

Proteins Proteins are compounds that contain carbon, hydrogen, oxygen and nitrogen.

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Proteins Proteins  made up of basic units (amino acids) Essential amino acids necessary to keep the body healthy. There are about 20 different amino acids. 9 of them are essential. different types of amino acids

peptide links

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Proteins

Biuret test for proteins

Add sodium hydroxide to protein sample. Then, copper sulphate is added drop by drop.

2cm3 of sodium hydroxide

1% copper sulphate solution added drop by drop

2cm3 of protein sample

Purple solution formed  Protein is present 15

Fibre 

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A carbohydrate consisting largely of cellulose and lignin from plant foods. Cannot be digested by the human body. It helps by adding bulk to the undigested waste  stimulates muscles of the large intestine to contract and move the waste along. Prevents constipation.

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Dietary Fibre / Roughage 

Organic nutrients

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Part of food we cannot digest e.g. cellulose & lignin from plant foods.

Best source: fruits, vegetables, wholemeal bread & wholegrain cereals such as oats, brown rice & wheat

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Dietary Importance of Fibre Provide bulk to intestinal contents - thus stimulate the muscle of the large intestine to contract & move the indigestible matter along.

Vitamins

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Organic nutrients needed in small amounts for good health. Fat-soluble vitamins stored in the body. Water-soluble vitamins cannot be stored in the body 

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Excess will be excreted.

Insufficient in the diet  deficiency diseases.

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Water-soluble vitamins Vitamins Thiamine (B1) Riboflavin (B2) Niacin B6 B12 C

Major sources Beans, peanuts, meat (especially pork), whole grains, eggs Dairy products, eggs, green leafy vegetables, yeast Meat, poultry, fish, peanuts Meat, poultry, fish, potatoes, sweet potatoes Meat, poultry, fish, eggs, dairy products Fruits (especially citrus fruits) and vegetables, strawberries, tomatoes, green leafy vegetables20

Fat-soluble vitamins Vitamin

Major sources

A

Dark yellow vegetables (such as carrots), green leafy vegetables, liver, eggs

D

Sunlight, fish liver oil, fortified milk

E

Vegetable oils, seeds, whole grains

K

Green leafy vegetables, cabbage, pork liver, intestinal bacteria

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Vitamin C (Ascorbic Acid) Deficiency Symptoms

Importance 

Essential for keeping the epithelia healthy

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Keeps teeth firm in gums

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Helps healing of wounds

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Aids iron absorption

Bleeding gums Loose teeth Bleeding under the skin Weakness Slow healing wounds

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Vitamin D (Calciferol) Importance 

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Helps in the absorption of phosphorus and calcium from the intestine Builds and maintains bones and teeth

Deficiency Symptoms 

Causes rickets. It is a disease found mainly in children when bones fail to harden properly leading to bowlegs and beaded ribs.

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Mineral

•Inorganic chemical elements •Essential to the body’s functions. •Regulate body processes. •Are quickly used or lost as waste products. •Examples include calcium, phosphorus and magnesium and iodine, iron and zinc.

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Calcium

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Importance For development of strong bones and teeth

Deficiency Symptoms   

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For blood clotting

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For muscle contraction

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Soft bones Osteoporosis (adults) Rickets (children) Slow blood clotting Weakness Slow healing wounds

For nerve and heart activity 25

Iron

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Importance Forms haemoglobin in red blood cells Transports oxygen as oxyhaemoglobin

Deficiency Symptoms  Anaemia 

Paleness of skin

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Fatigue

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Water 

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Enables nutrients to dissolve and be carried to the parts of the body where they are needed. Is needed for all the body’s functions  digestion of food  removal of excretory waste, maintenance of body temperature at 37°C  cushioning sensitive parts of the body such as the brain. 27

(Inorganic nutrient) 

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Acts as a medium for chemical reactions to occur. Acts as solvent and transport agent for: digested food, wastes, hormones etc. An essential/major components of: lubricant found in joints, digestive juices & blood. Helps to regulate body temperature (e.g. sweating)

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Water

Sources: milk, juices and soup. •Is lost during urination, perspiration and even breathing. •If not replaced, will lead to dehydration, causing muscle cramps and weakness.

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