Complete Notes on Food for CTET / TET - Part I || Sources and Components of Food || Nutrition in Plants || NCERT Based
This article summarizes the important contents on Food topic based on NCERT. This highlights important points which may be useful for competitive exams such as TET / CTET.
This article covers topics like Sources of Foods, Components of Food, Test for Carbohydrates, Proteins and Fats, Nutrition in Plants. To read about Nutrition in Animals (including Human), refer below link:
Sources and Components Of Food
The main sources of our food are plants and animals. Some plants have two or more edible (eatable) parts. E.g. Seeds of mustard plants give us oil and the leaves are used as a vegetable. Even Banana and Pumpkin plants have more than two edible plant parts.
- Animals which eat only plants are called herbivores .
- Animals which eat only animals are called carnivores .
- Animals which eat both plants as well as other animals are called omnivores .
Food Components:
The major nutrients (components) in our food are carbohydrates, proteins, fats, vitamins and minerals. In addition, food also contains dietary fibres and water.
The main carbohydrates found in our food are in the form of starch and sugars. Carbohydrates mainly provide energy to our body. Fats also give us energy. In fact, fats give much more energy as compared to the same amount of carbohydrates.
Foods containing fats and carbohydrates are also called ‘energy giving foods’ .
Sources of CarboHydrate: Potato, sweet potato, sugarcane, rice, Bajra, Papaya, mango, Maize, Melon, Wheat.
Sources of Fat: Nuts (Almonds, Cashew, etc), Groundnut, Til, Sunflower oil, Coconut oil, Mustard Oil, Soybean oil, Milk, Ghee, Butter, Cream, Meat, Fish, Egg
Proteins are needed for the growth and repair of our body. Food containing proteins are often called ‘body building foods' .
Sources of Proteins: Gram, Moong, Dal, Beans, Soyabeans, Peas, Milk, Paneer, Fish, meat, egg.
Vitamins help in protecting our body against diseases. Vitamins also help in keeping our eyes, bones, teeth and gums. Some of these are Vitamin A, Vitamin C, Vitamin D, Vitamin E and K. There is also a group of vitamins called Vitamin B-complex.
Vitamin A keeps our skin and eyes healthy. Vitamin C helps body to fight against many diseases. Vitamin D helps our body to use calcium for bones and teeth.
- Sources of Vitamin A: Milk, Fish oil, Papaya , Carrot, Mango
- Sources of Vitamin B: Liver, Whole grains (brown rice, barley, millet)
- Some sources of Vitamin C: Orange, Tomato, Guava, Lemon, Amla, Chili
- Some sources of Vitamin D: Liver, Milk, Butter, Fish, Egg. Our body also prepares Vitamin D in the presence of Sunlight
Minerals are needed by our body in small amounts. Each one is essential for proper growth of body and to maintain good health.
- sources of iodine: Fish, salt, ginger, spinach
- sources of phosphorous: Milk, Banana, Chili, Whole grains (brown rice, barley, millet)
- sources of iron: liver, spinach, apple
- sources of calcium: milk, egg
Roughage does not provide any nutrient to our body, but is an essential component of our food and adds to its bulk. This helps our body get rid of undigested food.
Water helps our body to absorb nutrients from food. It also helps in throwing out some wastes from body as urine and sweat. Normally, we get most of the water that our body needs from the liquids we drink — such as water, milk and tea.
Effect of Unbalanced diet:
It can be very harmful for us to eat too much of fat rich foods and we may end up suffering from a condition called obesity.
A person may be getting enough food to eat, but sometimes the food may not contain a particular nutrient. If this continues over a long period of time, the person may suffer from its deficiency. Deficiency of one or more nutrients can cause diseases or disorders in our body. Diseases that occur due to lack of nutrients over a long period are called deficiency diseases .
E.g. Vitamin A deficiency: Loss of Vision, Vitamin B deficiency: Beriberi, Vitamin C deficiency: Scurvy, Vitamin D deficiency: Rickets, Iodine deficiency: Goiter, Iron deficiency: Anaemia etc.
If a person does not get enough proteins in his/her food for a long time, he/she is likely to have stunted growth, swelling of face, discoloration of hair, skin diseases and diarrhea.
If the diet is deficient in both carbohydrates and proteins for a long period of time, the growth may stop completely. Such a person becomes very lean and thin and so weak that he/she may not even be able to move.
All deficiency diseases can be prevented by taking a balanced diet.
Test for presence of Carbohydrates, Fats and Proteins:
The tests for presence of carbohydrates, proteins and fats are simpler to do as compared to the tests for other nutrients. For carrying out these tests, we will need solutions of iodine, copper sulphate and caustic soda.
- Copper sulphate solution can be prepared by dissolving 2 gram (g) of copper sulphate in 100 milliliter (mL) of water.
- 10 g of caustic soda dissolved in 100 mL of water makes the required solution of caustic soda.
Test for Starch: Put 2-3 drops of iodine solution on small quantity of food item or raw ingredients. Observe if there is any change in the colour of the food item. A blue-black colour indicates that it contains starch.
Test for Protein: Add two drops of solution of copper sulphate and ten drops of solution of caustic soda on the powdered food item solution or paste. A violet colour indicates presence of proteins in the food item.
Test for Fats: Take a small quantity of a food item. Wrap it in a piece of paper and crush it. An oily patch on paper shows that the food item contains fat.
Nutrition in Plants:
Nutrition is the mode of taking food by an organism and its utilisation by the body.
The mode of nutrition in which organisms make food themselves from simple substances is called autotrophic nutrition (auto = self; trophos = nourishment). Therefore, plants are called autotrophs.
Animals and most other organisms take in ready made food prepared by the plants. They are called heterotrophs (heteros = other).
Photosynthesis — Food Making Process in Plants:
Leaves are the food factories of plants, The synthesis of food in plants occurs in leaves. Therefore, all the raw materials must reach there. Water and minerals present in the soil are absorbed by roots. Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves. These pores are surrounded by ‘guard cells’. Such pores are called stomata .
Water and minerals are transported to the leaves by the vessels which run like pipes throughout the root, the stem, the branches and the leaves. They form a continuous path or passage for the nutrients to reach the leaf.
The leaves have a green pigment called chlorophyll. It helps leaves to capture the energy of the sunlight. This energy is used to synthesise (prepare) food from carbon dioxide and water. Since the synthesis of food occurs in the presence of sunlight, it is called photosynthesis (Photo: light; synthesis : to combine). Light is so important to plants that their leaves grow in many patterns so as to catch the most sunlight.
It is a unique process on the earth. The solar energy is captured by the leaves and stored in the plant in the form of food. Thus, sun is the ultimate source of energy for all living organisms .
Oxygen which is essential for the survival of all living organisms is produced during photosynthesis.
Besides leaves, photosynthesis also takes place in other green parts of the plant — in green stems and green branches. The desert plants have scale- or spine-like leaves to reduce loss of water by transpiration. These plants have green stems which carry out photosynthesis.
During photosynthesis, chlorophyll containing cells of leaves, in the presence of sunlight, use carbon dioxide and water to synthesise carbohydrates. The process can be represented as an equation:
Carbon dioxide + water (In presence of chlorophyll and sunlight) --> Carbohydrate + oxygen
. During the process oxygen is released. The carbohydrates ultimately get converted into starch. The presence of starch in leaves indicates the occurrence of photosynthesis. The starch is also a carbohydrate.The leaves other than green also have chlorophyll. The large amount of red, brown and other pigments mask the green colour. Photosynthesis takes place in these leaves also.
Synthesis of plant food other than carbohydrates:
Plants synthesise carbohydrates through the process of photosynthesis. The carbohydrates are made of carbon, hydrogen and oxygen. These are used to synthesise other components of food such as proteins and fats. But proteins are nitrogenous substances which contain nitrogen. From where do the plants obtain nitrogen?
Nitrogen is present in abundance in gaseous form in the air. However, plants cannot absorb nitrogen in this form. Soil has certain bacteria that convert gaseous nitrogen into a usable form and release it into the soil. These soluble forms are absorbed by the plants along with water. Also, usually farmers adds fertilisers rich in nitrogen to the soil. In this way the plants fulfil their requirements of nitrogen along with the other constituents. Plants can then synthesise components of food other than carbohydrates such as proteins and fats.
Other modes of nutrition in plants:
There are some plants which do not have chlorophyll. They cannot synthesise their food. How do they survive and from where do they derive nutrition?
Like humans and animals such plants depend on the food produced by other plants. They use the heterotrophic mode of nutrition.
There is a plant called Cuscuta (Amarbel). It does not have chlorophyll. It takes ready made food from the plant on which it is climbing. The plant on which it climbs is called a host . Since it deprives the host of valuable nutrients, it is called a parasite . Mosquitoes, bed bugs, lice and leeches that suck our blood are also parasites.
There are a few plants which can trap insects and digest them. Such plants may be green or of some other colour. The pitcher-like structure of these plant is the modified part of the leaf. The apex of the leaf forms a lid which can open and close the mouth of the pitcher. Inside the pitcher there are hair which are directed downwards. When an insect lands in the pitcher, the lid closes and the trapped insect gets entangled into the hair. The insect is digested by the digestive juices secreted in the pitcher. Such insect-eating plants are called insectivorous plants . Insectivorous plants are partial heterotrophs.
You may have also seen fluffy umbrella-like patches growing on rotting wood during the rainy season.These organisms are called fungi. They have a different mode of nutrition. They secrete digestive juices on the dead and decaying matter and convert it into a solution. Then they absorb the nutrients from it. This mode of nutrition in which organisms take in nutrients in solution form from dead and decaying matter is called saprotrophic nutrition .
Plants which use saprotrophic mode of nutrition are called saprotrophs. Fungi also grow on pickles, leather, clothes and other articles that are left in hot and humid weather for long time. E.g. Mushroom. They do not have mouths like animals do. They are not like green plants as they lack chlorophyll and cannot make food by photosyntehsis.Many fungi like yeast and mushrooms are useful, but some fungi cause diseases in plants, animals and humans. Some fungi are also used in medicines. The fungal spores are generally present in the air. When they land on wet and warm things they germinate and grow.
Some organisms live together and share shelter and nutrients. This is called symbiotic relationship. For example, certain fungi live in the roots of trees. The tree provides nutrients to the fungus and, in return, receives help from it to take up water and nutrients from the soil. This association is very important for the tree.
In organisms called lichens, a chlorophyll-containing partner, which is an alga, and a fungus live together. The fungus provides shelter, water and minerals to the alga and, in return, the alga provides food which it prepares by photosynthesis.
Usually crops require a lot of nitrogen to make proteins. After the harvest, the soil becomes deficient in nitrogen. We Know that though nitrogen gas is available in plenty in the air, plants cannot use it in the manner they can use carbon dioxide. They need nitrogen in a soluble form. The bacterium called Rhizobium can take atmospheric nitrogen and convert it into a soluble form. But Rhizobium cannot make its own food. So it lives in the roots of gram, peas, moong, beans and other legumes and provides them with nitrogen. Most of the pulses (dals) are obtained from leguminous plants. In return, the plants provide food and shelter to the bacteria. Thus they have a symbiotic relationship.
This association is of great significance for the farmers. They do not need to add nitrogen fertiliser to the soil in which leguminous plants are grown.
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