Difference Between Phototrophs and Chemotrophs

Edited by Diffzy | Updated on: April 30, 2023


Difference Between Phototrophs and Chemotrophs

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Phototrophs and chemotrophs are two organisms about whom we’ll be discussing in this article. Both organisms are well-known because they have been studied. Some people are capable of preparing their own food, while others are not. They obtain their food from a different source. Phototrophs and chemotrophs are two different types of organisms. The energy source differs from one another.

Let’s look at their differences a bit in detail and enhance our knowledge about them.

Phototrophs vs Chemotrophs

The major distinction between Phototrophs and Chemotrophs is that Phototrophs use sunlight as a source of energy for photosynthesis, whereas Chemotrophs obtain energy through chemical processes and chemosynthesis. Chemosynthesis is not carried out by chemotrophs using sunlight. Chemotrophs get their energy by oxidising carbon molecules. Phototrophs are organisms that consume sunlight and convert it to chemical energy (Difference Between Phototrophs and Chemotrophs (With Table), n.d.).

Difference Between Phototrophs and Chemotrophs in Tabular Form

Parameters of Comparison Phototrophs Chemotrophs
Energy used The energy of light. Energy is obtained by oxidizing electron donors.
Process Photosynthesis Chemosynthesis
Sunlight required Yes No
Source used Sunlight Chemical compounds
Examples Green plants Nitrosomonas

What are Phototrophs?

Phototrophs are species that use photon capture to generate complex organic compounds (such as carbohydrates) and obtain energy. They employ light energy to perform a range of cell metabolic functions. It's a prevalent misperception that phototrophs must be photosynthetic to survive. Many phototrophs, but not all, photosynthesize, transforming carbon dioxide into organic material which can be used physically, functionally, or as a source for future catabolic processes.

Autotrophs and heterotrophs are two types of phototrophs. Photoautotrophs use light as a source of energy to repair carbon into simple sugars. Green plants, algae, and cyanobacteria are examples of photoautotrophs. Holographs are creatures that repair carbon dioxide in the atmosphere. Oxygenic photosynthetic organisms are phototrophs that employ chlorophyll to harvest light energy and divide water to generate oxygons.

So basically, the majority of well-known phototrophs are autotrophic, often known as photoautotrophs, and have the power to fix carbon. Now, Chemotrophs, on the other hand, get their energy through the oxidation of electron donors in their environment. Also,  Photoautotrophs use light as an energy source to synthesize their own food from inorganic chemicals. Photoautotrophs include green plants as well as photosynthetic microorganisms.

Holophytic organisms are photoautotrophic creatures that are photoautotrophic. These organisms use light to generate energy for food synthesis and can use carbon dioxide as their primary carbon source.

Chlorophyll is used by oxygenic photosynthetic organisms to collect light energy and oxidise water, dividing it into molecular oxygen. Anoxygenic photosynthetic bacteria, on the other hand, use a material called bacteriochlorophyll to capture light energy, thrive in watery conditions, and use light to oxidise chemical compounds like hydrogen sulphide rather than water.

Also, Phototrophs are frequently the food source for nearby heterotrophic life in an ecological environment. Plus, Plants are the most common phototrophic organisms in terrestrial areas, while algae (e.g., kelp), other protists (e.g., euglena), phytoplankton, and bacteria are found in aquatic environments (such as cyanobacteria). Moreover, the photic zone is the depth to which sunshine or artificial light can penetrate into water to allow photosynthesis to take place.

Furthermore, Cyanobacteria are prokaryotic organisms that perform oxygenic photosynthesis and can be found in a variety of environments, including fresh water, oceans, soil, and lichen. Because the organelle in plants that performs photosynthesis is derived from an endosymbiotic cyanobacterium, cyanobacteria do plant-like photosynthesis.  This bacterium can execute CO2 reduction processes using water as an electron supply. The capacity of cyanobacteria to thrive in oxygenic conditions, which are harmful to most anaerobic bacteria, may have provided the bacteria with an evolutionary advantage that allowed them to populate more effectively.

An autotrophic organism that employs light energy, an inorganic electron donor (e.g., H2O, H2, H2S), and CO2 as its carbon supply is known as a photolithoautotroph. Plants are one example (Phototroph, n.d.).

Photoheterotrophs are heterotrophic phototrophs, meaning they use light for energy but are unable to utilise carbon dioxide as their main carbon source. As a result, they rely on organic substances from the environment to meet their carbon needs, such as carbs, fatty acids, and alcohols. Purple non-sulfur bacteria, green non-sulfur bacteria, and heliobacteria are examples of photoheterotrophic organisms. According to recent studies, the oriental hornet and some aphids may be able to supplement their energy source by using light (Photoheterotroph, n.d.).


"Photo" stands for "light," and "tropism" stands for "turning." The phenomena of phototropism occurs when a plant bends towards the direction of light. Plants require light to stimulate the process of photosynthesis, which produces energy.

Auxins, a hormone found in plants' cells, react to photosynthesis by producing more protein and generating energy for the plant.

Photosynthesis is used by almost all plants to obtain more nourishment and energy. Positive phototropism causes the stem and shoots to turn towards the sunshine, whereas negative phototropism causes the roots to turn away from the light source. Gravitropism or geotropism is important in their development.

Now, in 1880, Charles Darwin studied phototropism in canary grass and oat coleoptiles with the help of his son, and published his findings in the book 'The Power of Movement in Plants.' They also noticed seedlings bending towards the light.

Moreover, they showed this by covering the tops of the oat coleoptiles, preventing photosynthesis. Likewise, they became phototropic once they coated the lower section of these coleoptiles. Furthermore, from this and other trials, he also discovered that the grass's tip (called coleoptiles) has a strong and firm perception of light and bends toward that, but the middle section activates protons, lowering the pH in the cells. So basically, this action causes the entire wall to become acidic, which activates an enzyme called expansions, which breaks down the structure and makes it less stiff.

The following is the mechanism of phototropism:

  • The plant is illuminated by light with a wavelength of 450 nanometers.
  • The photoreceptor receives light, reacts to it, and responds to it.
  • The proteins that accept blue light during phototropism are known as phototropins.
  • When exposed to light, auxin shifts to a darker side of the stem.
  • Auxin promotes a reduction in pH by releasing hydrogen ions in the shadowed part of the stem. As the pH drops, expansin is activated, causing the cells to enlarge and forcing the stem to bend towards the light.

What are Chemotrophs?

Chemotrophs are creatures that get their energy from oxidising electron donors in their surroundings. These molecules might be organic (chemoorganotrophs) or inorganic (inorganic chemoorganotrophs) (chemolithotrophs). Phototrophs, on the other hand, use solar energy and are referred to as chemotrophs. Chemotrophs are autotrophic or heterotrophic organisms. Chemotrophs live on the ocean floor, where sunlight can't reach them. Or it could be above ground, as in the case of iron bacteria.

Chemoorganotrophs, which oxidize organic chemicals for energy, and chemolithotrophs, which oxidise inorganic compounds for energy, are the two types of chemotrophs. Inorganic chemical sources such as hydrogen sulfide, ammonium ions, ferrous ions, and elemental sulfur provide electrons to chemolithotrophs. Acid thiobacillus ferrooxidans, Nitrosomonas, Nitrobacter, and Algae are examples of chemolithotrophs.

Chemoautotrophs generate all essential organic components from carbon dioxide, in addition to deriving energy through chemical processes. Inorganic electron sources such as hydrogen sulfide, elemental sulfur, ferrous iron, molecular hydrogen, and ammonia, as well as organic sources, are available to chemoautotrophs. Extremophiles, bacteria, or archaea that live in adverse settings (such as deep-sea vents) and are the principal producers in such ecosystems, make up the majority of chemoautotrophs.

Methanogens, sulfur oxidizers and reducers, nitrifiers, anammox bacteria, and thermoacidophiles are all examples of chemoautotrophs. Sulfolobus is an example of one of these prokaryotes. Chemolithotrophic growth can be extremely rapid, such as in the case of Hydrogenovibrio crunogenus, which doubles in under an hour.

Wilhelm Pfeffer created the term "chemosynthesis" in 1897 to describe the energy production by oxidation of inorganic compounds in conjunction with autotrophy—what is now known as chemolithoautotrophy. Later, the name was expanded to encompass chemoorganoautotrophy, making it a synonym for chemoautotrophy.


Chemoheterotrophs (also known as chemotrophic heterotrophs) are unable to fix carbon and produce organic molecules on their own. Chemoheterotrophs can be chemolithoheterotrophs, which use inorganic electron sources like sulfur, or chemoorganoheterotrophs, which use organic electron sources like carbohydrates, lipids, and proteins, which are considerably more frequent. Chemoheterotrophs are animals and fungi that get the majority of their energy from oxygen.  Chemoheterotrophs are halophiles (Chemotroph, n.d.).

Chemoautotrophs- What do they mean to us?

Chemoautotrophs are cells that utilize their energy to prepare them for usage. They don't get their energy from other molecules or substances; instead, they generate and form their own. Chemical reactions within the cells provide them with the energy they require.

Chemolithoautotrophs, which rely on inorganic energy sources, are among the most basic chemoautotrophs identified to date. All known chemoautotrophs are bacteria or Archaea at this time. These organisms are prokaryotic.


It indicates self-producing because the term has auto as a prefix. They don't get their energy from other species; instead, they manufacture food by performing chemical reactions. Chemoautotrophic nutrition refers to food that is created by chemical reactions.

The focus of the research is on inorganic chemicals that are utilized to synthesise various organic molecules with carbon content. As a result, after the final utilization of energy created by chemical reactions occurring within a cell, carbon dioxide will be formed.

Some Essential Information

To support its survival, an organism may devour other organisms or prepare its energy diet. Bacteria (prokaryotes) are common examples of organisms that do not rely on others for food and energy. Chemoautotrophs are organisms that require both organic and inorganic chemicals to carry out chemical reactions. They may also feed on other organisms in order to survive.

These species are important in maintaining a food chain in the ecosystem. There are food producers in the Biology food pyramid. These organisms convert energy into food for other organisms. Chemoheterotrophs, on the other hand, will be found as we progress up the pyramid. To make a living, these animals eat the lower-level producers. As a result, all animals and other living species, such as herbivores, carnivores, and omnivores, are chemoheterotrophs, meaning they are dependent on producers. When it comes to Chemoautrophs' core functions, life can only exist in environments where sunlight is not a primary source of energy (Chemotrophs, n.d.).

Main Differences Between Phototrophs and Chemotrophs In Points

Let’s study the differences between phototrophs and chemotrophs in detail.

  • Phototrophs are creatures that capture protons for the purpose of obtaining energy.
  • Chemotrophs are creatures that derive their energy by oxidizing electron sources.
  • Phototrophs get their energy primarily from sunlight.
  • Chemotrophs: Chemotrophs obtain their energy from the oxidising energy of chemical molecules.
  • Photoautotrophs and photoheterotrophs are two types of phototrophs.
  • Chemotrophs are divided into two types: chemoorganotrophs and chemolithotrophs.
  • Photoautotrophs include plants, algae, and cyanobacteria, while photoheterotrophs include purple non-sulfur bacteria, green non-sulfur bacteria, and heliobacteria.
  • Chemotrophs include bacteria such as Acid thiobacillus ferrooxidans, Nitrosomonas, Nitrobacter, and Algae (Difference Between Phototrophs and Chemotrophs, 2017).


Phototrophs and chemotrophs are two dietary classes that can be found in nature. Both autotrophic and heterotrophic types can be identified. As a result, their autotrophs make their own food, whilst their heterotrophs eat the food of other creatures. They can also be found in the food chain's primary and secondary levels. Phototrophs and chemotrophs differ mostly in their energy source.

Phototrophs and chemotrophs are two major types of organisms classified according to their nutritional needs. Phototrophs use sunshine to generate energy for their biological functions (solar energy). Solar energy is unavailable to chemotrophs. As a result, they are reliant on the energy generated via chemosynthesis. Chemotrophs oxidise chemicals to generate energy for their biological operations. Creatures that manufacture their own food and species that rely on foods produced by other organisms are included in both classes. Chemotrophs are the most common species on the planet. Many ecosystems rely on phototrophs to function properly. Photoautotrophs absorb carbon dioxide from the air and release oxygen back into it. Photoautotrophs are essential for the survival of other heterotrophic species. The distinction between phototrophs and chemotrophs is this.


  • Chemotroph. (n.d.). Retrieved from WIKIPEDIA: https://en.wikipedia.org/wiki/Chemotroph
  • Photoheterotroph. (n.d.). Retrieved from WIKIPEDIA: https://en.wikipedia.org/wiki/Photoheterotroph
  • Phototroph. (n.d.). Retrieved from WIKIPEDIA: https://en.wikipedia.org/wiki/Phototroph


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"Difference Between Phototrophs and Chemotrophs." Diffzy.com, 2024. Wed. 21 Feb. 2024. <https://www.diffzy.com/article/difference-between-phototrophs-and-chemotrophs-459>.

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