Nutrition

On a daily basis, we engage ourselves in lots of activities that require a huge amount of energy. Now, from where does this energy come? It comes from the food we consume. Food is vital for living organisms as it is required for the body to carry out lots of functions like growth, repair etc. all this is covered under the topic of nutrition. 

Let us now see the topic in detail. 

What is Nutrition? 

The process by which food is utilized by an organism is called nutrition.

Significance of Nutrition

• Nutrients supply the energy required by the organisms to perform various activities
• Nutrients provide raw materials required by the organisms for growth and repair

Constituents of Nutrition

• Macronutrients: They are required in large quantities such as carbohydrates, proteins, and fats
• Micronutrients: They are required in small quantities such as minerals and vitamins

Intake mode of Nutrition

• Autotrophic Nutrition: It is a mode of nutrition by which a few creatures, known as Autotrophs, utilize basic food material obtained from inorganic sources such as carbon dioxide and water, for instance, green plants and certain autotrophic microscopic organisms
• Heterotrophic Nutrition: It is a method of nutrition by which other living beings known as heterotrophs rely on autotrophs for their survival, for instance, animals and fungi

Heterotrophs utilize complex substances which are broken down into simpler ones using catalysts called enzymes.

Autotrophic Nutrition

Energy requirements of autotrophic organisms are fulfilled through the process of photosynthesis. It is the process by which autotrophs take in substances in the form of carbon dioxide and water and convert them into carbohydrates (Glucose) in the presence of sunlight and chlorophyll. 

• Carbohydrates prepared in photosynthesis serve as energy for green plants
• The carbohydrates which are not used immediately are stored in the form of starch in plant parts, which later serves as the internal energy reserve for the plant and is used when the need arises in future
• Similarly, excess energy derived is stored in the human body in the form of glycogen

Various events during Photosynthesis:

• Light energy is absorbed by chlorophyll
• Light energy is converted to chemical energy, which is used to split water molecules into hydrogen and oxygen
• Reduction of carbon dioxide to carbohydrates

These steps need not take place one after the other immediately in a sequence. For example, Desert plants store up carbon dioxide during the night and then convert it to an intermediate which is later on acted upon by the energy absorbed by the chlorophyll during the day.

Stomata

These are tiny pores present on the surface of the leaves. Large amounts of gaseous exchange take place in the leaves through these pores destined specifically for the purpose of photosynthesis. The exchange of gasses occurs all across the surface of stems, roots and leaves as well.

Opening and Closing of the Stomata

• It is a function of the guard cells
• The guard cells swell due to the inflow of water into them, thereby causing the stomatal pore to open
• In contrast, the pore closes when the guard cells shrink
• To avoid water loss, the plant closes these pores when it does not need carbon dioxide for photosynthesis

Heterotrophic Nutrition

The mode of nutrition where one organism obtains food from another organism is called heterotrophic nutrition. Organisms, other than green plants and blue-green algae which cannot make food for themselves follow the heterotrophic mode of nutrition. 

Nutritive Strategies

• The type of nutrition differs and relies upon the kind and accessibility of food material and the intake method of the organisms
• A few organisms break down the food outside their bodies and afterwards retain it, for instance, parasites like bread moulds, yeast, and mushrooms
• Others take in entire food material and separate it inside their bodies. the best example of this is us, humans
• Some different organisms get nutrition from plants or animals simultaneously, without killing them
• This parasitic nutritive procedure is used by a wide variety of natural substances like Cuscuta (Amar bel), ticks, lice, bloodsuckers, and tapeworms

Nutrition in various organisms

• In organisms with single cells, food may be ingested by the entire surface, for example, Amoeba

• It consumes food by its temporary finger-like projections from the cell surface which fuse the food particle forming a food vacuole
• Inside the food vacuole, complex substances are broken down into simpler ones which later on diffuse into the cytoplasm 
• The leftover undigested particles are moved towards the outer layer of the cell and afterwards thrown out

• In Paramecium, which is also a single-celled organism, the cell has a definite shape and food is ingested at a specific spot
• Food is moved to this spot by the movement of cilia which lines the entire surface of the cell
• As the complexity of the organism increases, different parts of the organism become specialized to perform different functions, for example, humans

Conclusion 

In this article, we have covered the significance, constituents, the various modes of intake of nutrition and their explanation. Nutrition is the sum total of the processes by which the organisms obtain food and utilize it for carrying out their activities such as maintenance and growth. Under autotrophic nutrition, simple organic matters such as water and carbon dioxide are used by the organisms to synthesize food. Whereas, under heterotrophic nutrition, the organism is not able to prepare food on its own and depends on others for its nutrition. Heterotrophs are classified into three categories, namely parasites, holozoic, and saprophytes.