Autotrophic and Heterotrophic Nutrition: Introduction, Types of Autotrophic Nutrition (For CBSE, ICSE, IAS, NET, NRA 2022)

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Introduction to Autotrophic Nutrition

  • Autotrophic means self-nutrition.
  • This is a process in which an organism prepares its own food from simple inorganic material like water, mineral salts, and carbon dioxide in the presence of sunlight.
  • Some examples of autotrophic nutrition are blue-green algae and cyanobacteria.
  • Food or source of energy is synthesized using the energy from the sunlight.
  • Chlorophyll a green pigment is essential as it entraps the energy from sunlight.
  • This mode of nutrition is shown by all green plants and bacteria.

Types of Autotrophic Nutrition

  • Photo-autotrophic nutrition (Sunlight is the energy source)
  • Chemo-autotrophic nutrition (Chemicals are the energy source)


  • This is the process by which plants prepare their own food in the presence of sunlight.
  • This process mostly occurs in the leaves of the plants.
  • The solar energy is transformed into chemical energy to produce starch.
  • This process helps plants produce glucose to be able to produce energy for the transportation of water and minerals.
  • Factors that encourage or inhibit photosynthesis:
    • Light
    • Oxygen
    • Temperature
    • CO2
  • The process of photosynthesis is represented in the equation form

Steps in Photosynthesis

Steps in Photosynthesis


  • These are the food factories of the plant.
  • The process of photosynthesis occurs in the mesophyll layer of the leaf.


This is present in the lower epidermis of the leaf which uses carbon dioxide from the air.


These are responsible for absorbing minerals and water from the soil and carry it to the different parts of the plant.

Light Reaction and Dark Reaction

Light Reaction and Dark Reaction
Light ReactionDark reaction
A light dependent reaction.No light is needed.
Required to generate molecules like ATP.No such molecules are generated.
Reaction occurs in the thylakoid membrane of the chloroplast.Reaction occurs in stroma present in the chloroplast.

Chemo-Autotrophic Nutrition (Chemicals Are the Energy Source)

  • Here chemical energy is used by the organism to make their own food.
  • Sunlight is not needed.
  • Chemo-autotrophic nutrition is possible only during nighttime.
  • For e. g. Nitrosomonas

Sources for Chemoautotrophic Nutrition

Sources for Chemoautotrophic Nutrition

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