Class 6 Science

Components of Food

Learning Goals

The main components of foods are carbohydrates, protein, fats, vitamins and minerals. These are called nutrients.

Carbohydrates

Carbohydrates are also called energy giving food. It is the main sources of energy. It is made up of carbon, hydrogen, and oxygen. There are three types of carbohydrates.

Test for carbohydrate

You can test for presence of carbohydrate in a food by using the iodine test. This test is based on the concept that iodine makes a dark blue complex with starch.

Carbohydrate is stored in the form of starch in plants. So, when a drop of iodine is poured on mashed potato, the colour of mashed potato turns dark blue. This shows the presence of starch in potato.

Protein

Protein helps in body growth and repairs the tissues so it is also called body building food. We get protein from milk, eggs, meat, fish and all kinds of pulse. Protein molecule is made of a large number of smaller molecules called amino acid. The daily requirement of protein for adults is 1 gram per kilogram of the body weight. When the body is building new tissue, more proteins are required, so growing children and pregnant lady need more protein.

Test for protein

Soak dal (lentil) for about 4 hours in water and make a paste of soaked dal. Take this paste in a test tube and add 5 mL sodium hydroxide in it. After that, add about 5 drops of copper sulphate solution to the test tube and shake well. The colour of the mixture turns violet. This shows the presence of protein in dal.

Fat

Fats are made up of carbon, hydrogen and oxygen. Butter, ghee, milk, egg-yolk, nuts and cooking oils are the major sources of fat in our food. An adult needs about 35 g fat everyday. Our body stores the excess energy in the form of fat. This stored fat is used by the body for producing energy as and when required so fat is considered as energy bank in our body. Fats are essential for the absorption of vitamins A, D, E and K in the body. Fat in our body also prevents heat loss from the body surface.

Test for fat

This is a simple test. Wrap potato chips in tissue paper and crush them. After that unwrap the tissue paper and look at it against light. The tissue paper would appear translucent. This confirms the presence of fat in potato chips.

Vitamins

Vitamins are complex organic compounds which are essential for the growth and maintenance of our body. It does not provide energy. Our body requires vitamins A, C, D, E, K and B-complex. Our body can make only two vitamins, Vitamins D and K so other vitamins must be present in our food. The B complex vitamin is a mixture of several water- soluble vitamins. The important vitamins of this group are the vitamin B1, B2, B3, B4, B6, B9 and B12.

Minerals

Minerals are required by our body in very small quantities. Iron, Iodine, calcium, phosphorus, sodium and potassium are common minerals. The sources of these animals are plants and animals.

Deficiency Diseases

A disease which happens because of deficiency of a particular nutrient is called deficiency disease. Following table shows deficiency diseases because of deficiency of various nutrients.

Vitmains/MineralsDeficiency DiseasesSymptoms
Vitamin ANight blindnessPoor vision, loss of vision in darkness
Vitamin B1BeriberiWeak muscles, fatigue
Vitamin CScurvyBleeding gums
Vitmain DRicketsBent bones
CalciumOsteomalaciaWeak bones, tooth decay
IodineGoitreSwelling in neck
IronAnaemiaGeneral weakness, fatigue

Dietary fiber

The fibrous indigestible material present in any food is termed as dietary fibre or roughage. It helps in preventing constipation. It adds bulk to the food and gives a sense of fullness after the meal. Salad, vegetables, sprouted grains and fruits are the sources of roughages.

Balanced Diet

The diet which contains all the essential nutrients in the right proportion is called a balanced diet. The food we eat must have all the nutrients. It should provide the required energy. Deficiency of one or more nutrients in our food for a long time may cause certain diseases or disorders.