✍️ Concept of Nutrition and its importance
The process of food intake by animals is known as Nutrition . The nutritive elements present in food provide energy for various bio-chemical reactions and leads to physical growth of the body. This process of obtaining the food necessary for growth and healthy functioning of the body is known as nutrition.
Nutrients are the food substances which provide energy to living beings and synthesize new cellular substances.
All living beings require food and the nutritive elements present therein, to perform various complex chemical reactions of the body. The nutritive elements present in the food make possible the growth of living organisms, repair of the damage, development, protection from various diseases, control of various activities reproduction etc. If food is not made available all the physical processes and functions of the body will cease.
Body of living beings is like an engine of a vehicle. Like the engine, even body needs fuel. Even the body requires continuous input of fuel to perform various activities.
As soon as, sufficient fuel is not made available, even the body, like an engine will stop functioning. The reason behind it is the fact that the engine needs power to run, which is provided to it by the fuel.
Similarly our body also needs energy which is provided by the food and nutritive substances. Food and nutritive substances are needed to maintain the body temperature and also to sustain the continuous growth taking place in the body.
✍️ Types of Nutrition
On the basis of the mode of nutrition living beings can be divided into two main divisions (a) Autotrophs (b) Heterotrophs
Green plants contain a substance named chlorophyll. Hence, they prepare their own food using carbon-di-oxide, water and solar energy obtained from their environment. They are known as the autotrophs.
Some bacteria like sulphur bacteria, nitrifying bacteria, iron bacteria are also autotrophs. They obtain the energy required to prepare their food by oxidising sulphur, nitrogen and iron compounds. They are known as the chemoautotrophic.
Organism which a r e not able to synthesise their own food and depend on other living beings for their food, are known as the heterotrophs. Heterotrophic nutrition can be of the following types:
(a) Holozoic Nutrition : It is a type of nutrition in which the organism ingest other living beings or the carbonic substances made by them. Such type of organisms are known as holozoic living beings. They have been classified, on the basis of the source of their food, as under :
(i) Herbivores : Herbivors are the animals which depend on plants, directly, for their food. Examples: goat, cow, deer etc.
(ii) Carnivores : Animals which consume other animals, as their food are known as carnivores. Examples : Lion, tiger etc. Some plants are insectivorous for example : Pitcher plant, Utricularia, Drosera etc.
(iii) The Omnivores : The animals which consume both, plants and animals in the form of their food are known as omnivores. Examples : Rat, Pig, Human beings etc.
(b) Parasites : The organisms which reside inside or on the body of plants and animals and obtain their food from these plants and animals are known as parasites. These parasites may be of two types :
* Ectoparasite : Parasites which obtain their nourishment by attaching themselves to the host skin/surface, are known as ectoparasites. Example : Lice, Mosquito, Bedbug (animals); Cuscuta (plant).
* Endoparasite : Parasites which obtain their food by entering into the bodyorgans, like intestine, body cavity, liver, blood etc of their host are known as the endoparasites. Examples : Liver fluke, tape worm, plasmodium etc.
(c) Symbionts : The organisms which obtain their nourishment by living together are known as the symbionts. In symbiosis type of nourishment, different species live together and benefit each other. The two species living together does not cause any harm to each other. Examples : Algae and fungi together form lichen. They spend their entire life with each other.
(d) Saprobic Nutrition : Some organisms obtain their nourishment from the dead and decaying organisms. They are known as saprophytes and their mode of nourishment is of saprobic type. Examples : Microbes, fungi, some protozoa etc.
✍️ Nutrition in Plants
All living beings need food to remain alive. Energy is obtained from food. The body conducts various vital activities with this energy. If the body does not get food, all the activities and functions of our body will stop. In plants the prominent method of food formation is photosynthesis.
Photosynthesis in plants is an important activity from the perspective of environmental balance. During this activity the plant synthesize food in the presence of chlorophyll and sunlight using carbon-di-oxide and water present in the atmosphere and soil respectively and in return makes available the vital gas – oxygen. There is a vast difference in method of obtaining energy in plants and animals.
Animals cannot synthesize their own food and obtain it from green plants. On the other hand, green plants use solar energy and converts it into chemical energy. The energy is stored in the form of Adenosine – triphosphate (ATP) and reduced Nicotinamide adenine-di-phosphate (NADPH).
Plants use this energy for reduction of carbon-di-oxide. The entire process leads to the synthesis of carbohydrates, from which the animals obtain their food. The process of absorption of solar energy by green plants and converting it into chemical energy is known as photosynthesis.
(2) Photosynthetic Pigments
All photosynthetic organisms obtain light energy and converts it into chemical energy. This work is performed by the pigments. These pigments remain arranged in specific organelles which lie scattered in the cytoplasm.
Haeckel coined the term ‘plastid’ for these organelles. They are present in all plants except the fungi and prokaryotes like bacteria and blue green algae. Chloroplasts : These are green coloured plastids. Their green colour is because of the chlorophyll pigment present in them.
The plants and leaves appear green because of their presence. Their function is to perform food by photosynthesis. There are two distinct regions in chloroplasts – Stroma and Grana.
(i) Stroma : It forms the matrix of chloroplasts. The ribosomes which synthesize proteins, remain scattered in it. The dark reaction of photosynthesis takes place in this part of the chloroplast.
(ii) Grana : The light reaction of photosynthesis occurs in this part of the chloroplast. There are 40-60 grana in each chloroplast. In the granum region are present numerous plate-like or disc like structures, arranged like a stack of coins. These structures are known as the thyllakoid.
In higher plants four types of chloroplast pigments are present. The two green pigments are the chlorophyll a and b and the orange and yellow coloured pigments which are known as t he carotene and xanthophyll respectively.
(3) Mechanism of Photosynthesis
Carbon-di-oxide and water are the two major raw materials of photosynthesis. Chlorophyll and other pigments absorb light energy and transform it into chemical energy.
The process of photosynthesis, basically, completes in two steps : (i) Light reaction (ii) Dark reaction
(i) Light Reaction : During this process the radiant energy of the sun is converted into chemical energy. Following are the main processes of this step of photosynthesis :
(1) Absorption of light of definite wavelength by chlorophyll
(2) Excitation of chlorophyll
(3) Photolysis of water takes place.
(4) Oxygen is evolved
(5) Conversion into chemical energy: The ATP formed stores the energy and the reducing power NADPH is synthesized. This step is light-dependent, hence is known as the light reaction or the photo-chemical reaction. This process takes place in thyllakoid membrane present in the chloroplast.
(ii) Dark Reaction : During this step of photosynthesis ‘synthesis’ occurs. Here Carbohydrates are formed from carbondi-oxide. This process does require light, hence is known as the dark reaction. It takes place in the stroma of the chloroplast.In this process, there is fixation and reduction of carbon-di-oxide. The first stable product of this reaction process is PGA (phosphoglyceric acid), which is a three carbon molecule. Hence this cycle is also known as the C3 cycle or the Calvin cycle.
(4) Factors affecting photosynthesis
The factors affecting photosynthesis can be divided into two main types : External factors and Internal factors. I. External factors : This involves sunlight, carbon-di-oxide concentration, oxygen, temperature and water. II. Internal factors : Chlorophyll is a major factor under this category.
(5) Bacterial photosynthesis
Bacterial photosynthesis is a special type of photosynthetic process which takes place in some major types of bacteria. During this process too carbon-di-oxide is reduced by using solar energy – example : Cyanobacteria, Purple bacteria.
✍️ Major Components of Food
The complex chemical substances present in food, which are essential in proper amount, to accomplish different types of reactions in the body and to keep it healthy, are known as the components of food or Nutrients. Nutrients have been classified into the following six types :
- Fat Protein
- Mineral salts
Although water does not provide for any nourishment as such, but since it is essential for different physical processes, it has also been included among the nutrients.
There is one more substance which is not nutritive but must be a part of our food : Roughage or food fiber. In the animal food it is majorly the indigestable plant cell-wall part. It is helpful in removal of the residue, left after food digestion, from the body.
✍️ Nutrition in Animals
The vegetation obtains carbon-di-oxide from the atmosphere and converts it into carbohydrates by the process of photosynthesis. Animals consume these vegetation or other animals which in turn eat plants to obtain their energy.