Carbon and energy requirements of autotrophic organisms are fulfilled by:

Autotrophic organisms, such as green plants, algae, and certain bacteria, fulfill their carbon and energy requirements through the process of photosynthesis [3]. During this process, autotrophs take in inorganic substances like carbon dioxide and water from the environment and convert them into organic molecules like carbohydrates (glucose) using sunlight and chlorophyll [2]. Carbon dioxide serves as the primary carbon source, which is fixed into organic compounds via pathways like the Calvin cycle [6]. The energy from sunlight is captured and stored in the form of chemical energy within these carbohydrates [5]. While the immediate energy needs are met by utilizing these carbohydrates, any excess is stored as starch for future use [1]. Other processes like gluconeogenesis and glycogenesis are metabolic pathways related to glucose synthesis from non-carbohydrates and glycogen formation, respectively, rather than the primary mode of autotrophic nutrition.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > 5.2.1 Autotrophic Nutrition > p. 81
2. [3] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 1: Ecology > a) Primary producers - Autotrophs (self-nourishing) > p. 6
3. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 10: Life Processes in Plants > In a Nutshell > p. 150
4. [6] https://pmc.ncbi.nlm.nih.gov/articles/PMC3067309/
5. [5] https://www.sciencedirect.com/topics/medicine-and-dentistry/carbon-dioxide-fixation