Carbon source (biology)

This article is about a concept in biology. For the concept in climate change science, see greenhouse gas emissions.

Cycle between autotrophs and heterotrophs. Autotrophs use light, carbon dioxide (CO₂), and water to form oxygen and complex organic compounds, mainly through the process of photosynthesis (green arrow). Both types of organisms use such compounds via cellular respiration to both generate ATP and again form CO₂ and water (two red arrows).

The molecules that an organism uses as its carbon source for generating biomass are referred to as "carbon sources" in biology. It is possible for organic or inorganic sources of carbon. Heterotrophs must use organic molecules as both are a source of carbon and energy, in contrast to autotrophs, which can use inorganic materials as both a source of carbon and an abiotic source of energy, such as, for instance, inorganic chemical energy or light (photoautotrophs) (chemolithotrophs).

The carbon cycle, which begins with a carbon source that is inorganic, such as carbon dioxide and progresses through the carbon fixation process, includes the biological use of carbon as one of its components.^[1]

Types of organism by carbon source

Heterotrophs

This section is an excerpt from Heterotroph.[edit]

A heterotroph (/ˈhɛtərəˌtroʊf, -ˌtrɒf/; from Ancient Greek ἕτερος (héteros) 'other' and τροφή (trophḗ) 'nutrition') is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but not producers. Living organisms that are heterotrophic include all animals and fungi, some bacteria and protists, and many parasitic plants. The term heterotroph arose in microbiology in 1946 as part of a classification of microorganisms based on their type of nutrition. The term is now used in many fields, such as ecology, in describing the food chain.

Autotrophs

This section is an excerpt from Autotroph.[edit]

An autotroph is an organism that can convert abiotic sources of energy into energy stored in organic compounds, which can be used by other organisms. Autotrophs produce complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide, generally using energy from light or inorganic chemical reactions. Autotrophs do not need a living source of carbon or energy and are the producers in a food chain, such as plants on land or algae in water. Autotrophs can reduce carbon dioxide to make organic compounds for biosynthesis and as stored chemical fuel. Most autotrophs use water as the reducing agent, but some can use other hydrogen compounds such as hydrogen sulfide.