An organism deriving energy by ingesting intermediates or building blocks that it is incapable of creating on its own
Supplement
Chemotrophs are organisms that obtain energy through chemical process called chemosynthesis rather than by photosynthesis. Chemosynthesis is carried out by chemotrophs through the oxidation of electron donors in the environment. Chemotrophs may be chemoautotroph or chemoheterotroph.
Chemoheterotrophs are chemotrophs that are heterotrophic organisms. They are not capable of fixing carbon to form their own organic compounds. They may be further classified as chemolithoheterotrophs or chemoorganoheterotrophs. Chemolithoheterotrophs are those that utilize inorganic energy sources whereas chemoorganoheterotrophs are those using organic energy sources. Chemoorganoheterotrophs may be further grouped based on the kind of organic substrate and compound they use. Decomposers obtain these substrates and compounds from dead organic matter. Herbivores and carnivores derive theirs from living organic matter.
Most chemoheterotrophs obtain energy by ingesting organic molecules like glucose. In contrast, chemoautotrophs are autotrophs that use chemical energy to produce carbohydrates. They utilize inorganic compounds such as hydrogen sulfide, sulfur, ammonium, and ferrous iron as reducing agents, and synthesize organic compounds from carbon dioxide.
It may surprise you to learn this, but you are actually a chemoheterotroph!
“Chemoheterotroph” is the term for an organism which derives its energy from chemicals, and needs to consume other organisms in order to live. That means you: your body gets its energy from food, and you must consume other organisms such as plants and animals in order to survive.
All organisms must solve two problems in order to survive: they must be able to obtain energy, and they must be able to obtain cellular “building materials” such as proteins, lipids, and carbohydrates.
Most organisms that consume organic material use it for both energy and building materials. Animals and fungi both, for example, obtain energy by breaking down our food, and also get the building materials for our own cells from the food we eat.
A few rare organisms, however, use inorganic chemicals for energy, and yet cannot make their own building materials. These organisms – almost always bacteria – require both inorganic chemical energy sources, and other organisms whose organic materials they can consume, in order to survive.
All animals are chemoheterotrophs. So are fungi – although fungi may look like plants, they don’t perform photosynthesis, but rather derive their energy by breaking down organic material in soil.
Many bacteria are also chemoheterotrophs, including many bacteria that live inside the human body, many infectious bacteria, and some sulfur bacteria.
The chart below may be useful for determining whether a given organism is a chemoheterotroph:
Function of Chemoheterotrophs
Chemoheterotrophs play a big role in most ecosystems.
While “producers” at the bottom of an ecosystem’s energy pyramid make energy and organic materials from scratch, the upper levels of the pyramid are usually chemoheterotrophs who feed on those producers. Herbivores, carnivores, scavengers, and decomposers are all chemoheterotrophs.
Chemoheterotrophs take materials from plants and chemoautotrophs and recycle them in a complex web of life, where materials are used over and over again.
Types of Chemoheterotrophs
Chemoorganoheterotrophs – Eaters of Living Things
“Chemoorganoheterotroph” is a mouthful. But we’ve seen what “chemotroph” and “chemoheterotroph” mean.
“Chemoorganoheterotroph” just adds the term “organo,” for “organic” molecules. Organic molecules are carbon-containing molecules such as proteins, lipids, sugars, etc. that are usually associated with life.
Chemoorganoheterotrophs, then, are eaters of organic molecules – and where do you find organic molecules? Inside of living or dead organisms.
Chemoorganoheterotrophs, then, include herbivores, carnivores, scavengers, and decomposers. They include all fungi and animals.
Chemolithoheterotrophs – Stone Eaters
Just as “organo” is the Greek root word for organic materials, “litho” is the Greek word root for “stone.”
Chemolithoheterotrophs are organisms that derive their energy from inorganic minerals or other geological processes. Food sources for chemolithotrophs can include elemental sulfur and elemental gas.
Chemolithoheterotrophs are generally bacteria. Because deriving energy from inorganic minerals is not as efficient is digesting sugars using cellular respiration, organisms that use this energy source are generally small and simple.
Chemolithoheterotrophs can be found in places such as the sea floor or underground water sources, where both their chemical food sources and organic materials are found.
They may obtain their organic compounds be feeding on other bacteria, or on dead material that settles in sea floors and river beds from other organisms.
Examples of Chemoheterotrophs
Humans
It is easy to see how humans are chemoheterotrophs! We eat food every day. That food is made from animals, plants, and other organisms. We break down the organic chemicals from their cells to both obtain our own energy, and building materials for our own bodies.
Mushrooms
Mushrooms and other fungi may look like plants, but they are actually more like animals than like plants.
Fungi derive their energy from breaking down organic material. Often it’s organic material that is already dead, or is not well-defended by its host immune system.
Mushrooms can commonly be found growing in rich soil – which is made rich by the breakdown of the bodies of dead plants and animals – or on dead trees, old fruits, and other sources of organic material that do not have an immune system to fight the fungus off.
Some fungi can even attack living animals and infect them despite the immune response, though these are fairly rare. The Ophiocordyceps fungus, for example, attacks and digests living insects. Very rarely – usually in people whose immune systems are not healthy and strong – fungi can even attack healthy humans and cause dangerous infections.
Lithotrophic Bacteria
Almost all chemolithotrophs are autotrophs that do not need to consume other organisms to survive.
Likewise, almost all heterotrophs are organochemotrophs, organisms which obtain energy and organic compounds from the same source.
But a few species of bacteria that derive their energy from minerals have also developed the ability to use organic materials made by other organisms instead of making their own.
A few may even have lost the ability to make their own organic materials, meaning that they now require the presence of other organisms as well as their mineral energy source in order to survive.
Related Biology Terms
Chemotroph – Any organism that obtains its energy from chemicals. This includes chemoautotrophs such as sulfur bacteria, and chemoheterotrophs such as animals and fungi.
Energy pyramid – A diagram which shows how energy flows through different types of organisms within an ecosystem.
Heterotroph – Any organism which must eat other organisms in order to survive. This includes animals and fungi, and some bacteria.
Chemotrophs are a class of organisms that obtain their energy through the oxidation of inorganic molecules, such as iron and magnesium. The most common type of chemotrophic organisms are prokaryotic and include both bacteria and fungi. All of these organisms require carbon to survive and reproduce. The ability of chemotrophs to produce their own organic or carbon-containing molecules differentiates these organisms into two different classifications–chemoautotrophs and chemoheterotrophs.
Figure: Organismal and environmental interactions in a wetland: sources of energy and carbon for each trophic level.
Chemoautotrophs
Chemoautotrophs are able to synthesize their own organic molecules from the fixation of carbon dioxide. These organisms are able to produce their own source of food, or energy. The energy required for this process comes from the oxidation of inorganic molecules such as iron, sulfur or magnesium. Chemoautotrophs are able to thrive in very harsh environments, such as deep sea vents, due to their lack of dependence on outside sources of carbon other than carbon dioxide. Chemoautotrophs include nitrogen fixing bacteria located in the soil, iron oxidizing bacteria located in the lava beds, and sulfur oxidizing bacteria located in deep sea thermal vents.
Chemoheterotrophs
Chemoheterotrophs, unlike chemoautotrophs, are unable to synthesize their own organic molecules. Instead, these organisms must ingest preformed carbon molecules, such as carbohydrates and lipids, synthesized by other organisms. They do, however, still obtain energy from the oxidation of inorganic molecules like the chemoautotrophs. Chemoheterotrophs are only able to thrive in environments that are capable of sustaining other forms of life due to their dependence on these organisms for carbon sources. Chemoheterotrophs are the most abundant type of chemotrophic organisms and include most bacteria, fungi and protozoa.
Key Points
Chemotrophs are organisms that obtain energy by the oxidation of electron donors in their environment.
Chemoautotrophs use inorganic energy sources to synthesize organic compounds from carbon dioxide.
Chemoheterotrophs are unable to utilize carbon dioxide to form their own organic compounds. Their carbon source is rather derived from sulfur, carbohydrates, lipids, and proteins
Photoautotrophs are microbes get their energy from light and their carbon for inorganic compounds. Chemoautotrophs are microbes that get their energy from chemicals and get their carbon from inorganic compounds. Photoheterotrphs are microbes that get their energy from light and carbon from organic compounds. Chemoheterotrophs get their energy from chemicals and carbon from organic compounds
Types of Metabolism
Photoautotrophs and Photoheterotrophs
Photoautotrophs and photoheterotrophs are organisms that rely on light as their source of energy to carry out cellular processes.
LEARNING OBJECTIVES
Differentiate photoautotrophs from photoheterotrophs
KEY TAKEAWAYS
Key Points
Phototrophs are organisms that carry out photon capture to acquire energy.
Photoautotrophs convert inorganic materials into organic materials for use in cellular functions such as biosynthesis and respiration and provide nutrition for many other forms of life.
Photoheterotrophs depend on light for their source of energy and mostly organic compounds from the environment for their source of carbon.
Key Terms
ATP synthase: an important enzyme that catalyzes the conversion of adenosine diphosphate into adenosine triphosphate.
photosynthesis: The process by which plants and other photoautotrophs generate carbohydrates and oxygen from carbon dioxide, water, and light energy in chloroplasts.
Phototrophs are organisms that use light as their source of energy to produce ATP and carry out various cellular processes. Not all phototrophs are photosynthetic but they all constitute a food source for heterotrophic organisms. All phototrophs either use electron transport chain or direct proton pumping to establish an electro-chemical gradient utilized by ATP synthase to provide molecular energy for the cell. Phototrophs can be of two types based on their metabolism.
Types of microbial metabolism: Flowchart summarizing the types of microbial metabolism.
Photoautotrophs
An autotroph is an organism able to make its own food. Photoautotrophs are organisms that carry out photosynthesis. Using energy from sunlight, carbon dioxide and water are converted into organic materials to be used in cellular functions such as biosynthesis and respiration. In an ecological context, they provide nutrition for all other forms of life (besides other autotrophs such as chemotrophs ). In terrestrial environments plants are the predominant variety, while aquatic environments include a range of phototrophic organisms such as algae, protists, and bacteria. In photosynthetic bacteria and cyanobacteria that build up carbon dioxide and water into organic cell materials using energy from sunlight, starch is produced as final product. This process is an essential storage form of carbon, which can be used when light conditions are too poor to satisfy the immediate needs of the organism.
Photoheterotrophs
A heterotroph is an organism that depends on organic matter already produced by other organisms for its nourishment. Photoheterotrophs obtain their energy from sunlight and carbon from organic material and not carbon dioxide. Most of the well-recognized phototrophs are autotrophs, also known as photoautotrophs, and can fix carbon. They can be contrasted with chemotrophs that obtain their energy by the oxidation of electron donors in their environments. Photoheterotrophs produce ATP through photophosphorylation but use environmentally obtained organic compounds to build structures and other bio-molecules. Photoautotrophic organisms are sometimes referred to as holophytic.
Chemoautotrophs and Chemoheterotrophs
Chemoautotrophs and chemoheterotrophs make their food using chemical energy rather than solar energy.
LEARNING OBJECTIVES
Compare chemoautotrophs and chemoheterotrophs
KEY TAKEAWAYS
Key Points
Chemotrophs are organisms that obtain energy by the oxidation of electron donors in their environment.
Chemoautotrophs use inorganic energy sources to synthesize organic compounds from carbon dioxide.
Chemoheterotrophs are unable to utilize carbon dioxide to form their own organic compounds. Their carbon source is rather derived from sulfur, carbohydrates, lipids, and proteins.
Key Terms
inorganic molecule: lacks carbon and hydrogen atoms.
Chemotrophs are a class of organisms that obtain their energy through the oxidation of inorganic molecules, such as iron and magnesium. The most common type of chemotrophic organisms are prokaryotic and include both bacteria and fungi. All of these organisms require carbon to survive and reproduce. The ability of chemotrophs to produce their own organic or carbon-containing molecules differentiates these organisms into two different classifications–chemoautotrophs and chemoheterotrophs.
Organismal and environmental interactions in a wetland: sources of energy and carbon for each trophic level.
Chemoautotrophs
Chemoautotrophs are able to synthesize their own organic molecules from the fixation of carbon dioxide. These organisms are able to produce their own source of food, or energy. The energy required for this process comes from the oxidation of inorganic molecules such as iron, sulfur or magnesium. Chemoautotrophs are able to thrive in very harsh environments, such as deep sea vents, due to their lack of dependence on outside sources of carbon other than carbon dioxide. Chemoautotrophs include nitrogen fixing bacteria located in the soil, iron oxidizing bacteria located in the lava beds, and sulfur oxidizing bacteria located in deep sea thermal vents.
Chemoheterotrophs
Chemoheterotrophs, unlike chemoautotrophs, are unable to synthesize their own organic molecules. Instead, these organisms must ingest preformed carbon molecules, such as carbohydrates and lipids, synthesized by other organisms. They do, however, still obtain energy from the oxidation of inorganic molecules like the chemoautotrophs. Chemoheterotrophs are only able to thrive in environments that are capable of sustaining other forms of life due to their dependence on these organisms for carbon sources. Chemoheterotrophs are the most abundant type of chemotrophic organisms and include most bacteria, fungi and protozoa.
LICENSES AND ATTRIBUTIONS
Chemoheterotroph
(both chemotrophic and heterotrophic → chemoheterotrophic)
Organic compounds also serve as our source of organic carbon from which our bodies are assembled, that is, the carbon structures making up proteins, nucleic acids, lipids, and carbohydrates (heterotrophic acquisition of organic carbon).
Note that the organic compounds that chemoheterotrophs consume are breakdown products of other organisms, that is, ecologically chemoheterotrophs are consumers.
