June 12, 2021


5 min read





In this article, we shall discuss nutrition and the components of human food.





The process in which food is obtained or manufactured, digested, absorbed, and converted into bodybuilding for proper functioning as well as for growth and energy is called nutrition. There are two categories of organisms depending upon nutrition e.g. autotrophic and heterotrophic organisms.

Autotrophic Organisms: Organisms obtain water, carbon dioxide, and minerals from their surrounding and manufacture their own food which is then utilized for growth and energy are called autotrophic organisms. e.g all plants and algae.

Heterotrophic Organisms: Those organisms that obtain their food from other living things and use it for growth and energy are generally termed heterotrophic organisms. e.g. all animals.

Nutrients: Components of food that an organism obtains and uses for energy or for the synthesis of new substances for normal growth are called nutrients. Regarding plants there two kinds of nutrients, (1) macronutrients (2) micronutrients. The nutrients which are needed in larger quantities,  known as macronutrients e.g. carbon, hydrogen, oxygen, nitrogen, magnesium, potassium, etc.  Similarly, the nutrients,  which are needed in smaller quantities known as micronutrients e.g. iron,  molybdenum, boron, zinc, chlorine, etc. . If any single nutrient is not available to plant, they do not grow normally and exhibit abnormalities.

Both micro and macronutrients play very important roles in plant life.  Some roles of both types of nutrient for plants are described below;

Macronutrients                     Role in plant’s life:

Phosphorus                          Component of ATP, DNA and RNA, Coenzymes and necessary for seed germination.   

Sulfur                                 Component of enzymes and vitamins.

Calcium                                 Regulates many enzymes,  a structural component of the cell wall, and helps in water movement in cells.

Potassium controls the opening and closing of stomata and reduces water loss from the leaves.

Nitrogen is a primary macronutrient and necessary for the development of plants.

Magnesium                             An essential element of the core of chlorophyll, so therefore important for photosynthesis.





Micronutrients                          Role in plant’s  life:

Zinc                                              Essential for enzymes in greater quantity.

Nickel                                          Takes part in nitrogen metabolism.

Iron                                               Helps In photosynthesis.

Copper                                          Component of several enzymes.

Chlorine                                         Involved in osmosis of water.

Manganese                                  Involved in photosynthesis, respiration, and nitrogen metabolism.

Boron                                             Necessary for flowering, fruiting crop reproduction, and formation of the cell wall.

Molybdenum                             Component of enzymes and important in the building of amino acids



                                   Components of Food

The nutritional requirements of humans and other higher animals are relatively more complex as compared to plants. Like other animals, the nutrients used by humans include lipids, proteins, vitamins, carbohydrates, nucleic acids as well as minerals. Besides these nutrients they also need water. Here we discuss the role of only 4 components of food.

  1. Proteins

Proteins are basically composed of amino acids. They are essential components of cytoplasm, membranes, and organelles. They are also the major part of muscles, ligaments, and tendons. They are present in the nails and hairs of animals including humans. So proteins are directly involved in the growth of humans and other animals. Many proteins are enzymes, so play roles to speed chemical reactions (metabolism) occurring in living things. One gram of protein contains 4 kilocalories of energy. Dietary sources of proteins are meat, eggs, grains, legumes, and dairy products such as milk butter, and cheese.


  1. Carbohydrates

Carbohydrates are the basic source of energy for all animals. Glucose is the most often used carbohydrate for energy. About half to 2/3 of the total calories every animal utilizes daily from carbohydrates. Besides glucose which is the basic carbohydrate, other useful carbohydrates are maltose, lactose, starch, and sucrose. One gram of carbohydrates contains 4 kilocalories of energy. Sources of carbohydrates are bread, pasta, beans, potatoes, bran, rice, and cereals.


  1. Lipids

The lipids present in food are composed of fatty acids bonded to glycerol. The fatty acids of lipids may be saturated or unsaturated.

Saturated fatty acids have their carbon atoms bonded to hydrogen atoms, while unsaturated fatty acids have some of their carbon atoms double-bonded in place of the hydrogen atoms. Actually, the lipids consisting of saturated fatty acids are solids at room temperature. The lipids containing unsaturated fatty acids are liquids at room temperature. The most common example of saturated fatty acids is the ‘butter’ which contains about 70% saturated and 30% unsaturated fatty acids.  On the other hand, sunflower oil contains nearly 75% unsaturated fatty acids. Lipids are used to form membranes, the sheath covering neurons, and some important hormones. Among all the components of the food of humans, lipids contain a larger quantity of energy. One gram of lipids contains 9 kilocalories of energy. Major sources of lipids are milk, butter, cheese, fish, mutton, mustard oil, coconut, and other dry fruits. Proteins and lipids are vital building components for the body but they can also be used for energy.

Some bad effects of lipids: Saturated fatty acids can increase the cholesterol level of a person. An increased cholesterol level however results in the clogging of arteries which ultimately resulting in heart diseases.

  1. Vitamins

Vitamins are chemical compounds that are needed in low quantity but are very important for normal growth and metabolism. They are of two types: fat-soluble vitamins (vitamins A, D, E, and K) and water-soluble vitamins (vitamins B complex and vitamin C). Fat-soluble vitamins are much less eliminated from the body as compared to water-soluble vitamins. It means that the level of water-soluble vitamins in the body decreases very quickly, which leads to vitamin deficiency.

Identification of Vitamin A: Vitamin A is the fat-soluble vitamin, identified in 1913. In rod cells of the retina of the eye, it combines with a protein known as opsin to form rhodopsin. When vitamin A is insufficient in the retina, the lack of rhodopsin makes it difficult to see in dim light.

Role of vitamin A: It takes part in cell differentiation, a process through which embryonic cells transform into mature cells with specific functions. It also involves bone growth and immune functions.



Vitamin C: It is also called Ascorbic acid. Actually, vitamin C is a water-soluble vitamin. It is needed to form collagen that gives support to connective tissues. Collagen is a fibrous protein needed for the healing of wounds. In the white blood cells, vitamin C enables the immune system to perform its function normally.

Sources: General sources of vitamin C are citrus fruits, (oranges, lemons, and grapes) leafy green vegetables and beef liver, etc.


Deficiency: The disease known as scurvy results from the lack of vitamin C. In this condition, the synthesized collagen does not work properly and remains unstable. Symptoms of scurvy involved muscle and joint pain, slow wound healing, and dry skin.             


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