22.3 Prokaryotic Metabolism

Prokaryotes are diverse.

The metabolism of a prokaryote is a reflection of its genome, since the pathways and genes that make up the metabolism are the same as those that make up the genes.
There are many different environments on Earth with different energy and carbon sources.
Prokaryotes have been able to live in every environment by using whatever energy and carbon sources are available.
There are many niches on Earth for prokaryotes, including involvement in nitrogen and carbon cycles, production of oxygen, decomposition of dead organisms, and thriving inside multicellular organisms, including humans.
The wide range of environments that prokaryotes occupy is possible because they have diverse metabolisms.

There is a wide range of conditions on Earth in terms of temperature, acidity, salinity, oxygen availability, and energy sources.

Prokaryotes are well-equipped to live in a wide range of environmental conditions.
Prokaryotes need a source of energy, a source of carbon, and some additional nutrition to live.

Cells are made of macromolecules and water.

Macromolecules are produced by the polymerization of smaller units.
When prokaryotes grow in nature, they need to get their nutrition from the environment.
Micronutrients are required in smaller or trace amounts, whereas macronutrients are required in large amounts.
Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur are just a few elements.

They are components of organic compounds.

All macromolecules have carbon as the major element.
Nitrogen is only 12 percent of the dry weight of a cell.
Nitrogen is a component of cells.

Most of the nitrogen available in nature is atmospheric nitrogen.

Nitrogen can be converted into an organic form by certain organisms.
Oxygen and hydrogen are part of water.
All organisms need a certain amount of Phosphorus to synthesise.
Sulfur is part of the structure of some of the vitamins and coenzymes.
K, magnesium, calcium, and Na are important macronutrients.
The structure and function of the prokaryotic cell are dependent on these elements.

Prokaryotes require metallic elements in small amounts.

These are referred to as trace elements.
Iron is needed for the function of the cytochromes.
Some prokaryotes require other elements as co-factors.

The way in which prokaryotes obtain energy and carbon source are both classified.

Table 22.3 summarizes these categories.
Different sources of energy can be used by prokaryotes.
Phototrophs trap the light's energy through the use of chlorophylls or the bacterium rhodopsin.

Chemotrophs can use organic compounds as energy sources.

Sulfur or iron compounds can be used as energy sources.

bacteria and Archaea are important in the carbon and nitrogen cycles due to the fact that they lived on Earth for nearly a billion years before photosynthesis produced significant amounts of oxygen for aerobic respiration

Different sources of energy and carbon compounds can be used by prokaryotes.

The prokaryotes are able to synthesise organic molecule from carbon dioxide.
Heterotrophic prokaryotes get carbon from organic compounds.
The terms that describe how prokaryotes obtain energy and carbon can be combined to make the picture more complex.
Photoautotrophs use energy from sunlight and carbon from carbon dioxide and water, while chemoheterotrophs use both energy and carbon from an organic chemical source.
Chemolitho autotrophs get their energy from compounds other than carbon dioxide.
The prokaryotes that get their energy from light are called photoheterotrophs.
The table below summarizes carbon and energy sources.

There is no niche in which prokaryotes are not present.

In the environments they occupy, prokaryotes play many roles.
They play a vital role in the carbon and nitrogen cycles.

The carbon cycle traces the movement of carbon from inorganic to organic compounds and back again, and carbon is one of the most important macronutrients.

Earth's major sources of carbon are land, the atmosphere, aquatic environments, and rocks.
The "four elements" first proposed by Empedocles are fire, water, earth, and air.
Carbon dioxide is removed from the atmosphere by land plants and then returned to the atmosphere via the respiration of other organisms.
Carbon is not readily available in rocks and sediments.

Producers, consumers, and decomposers of organic carbon compounds make up the majority of participants in the carbon cycle.

Plants andbacteria are the primary producers of organic carbon compounds.
A large amount of carbon is found in plants.
humus is a mixture of organic materials from dead plants that have resisted decomposition.
Consumers such as animals and other Heterotrophs use organic compounds generated by producers and release carbon dioxide to the atmosphere.
The majority of carbon dioxide in the atmosphere comes from the respiration of dead animals, plants, and humus.

There is a carbon cycle taking place in the environment.

The cycle is based on one-carbon compounds.
Methane is produced by prokaryotes, mostly archaea.
This methane moves into the zone above the sediment, which is richer in oxygen and supportsbacteria called methane oxidizers that oxidize methane to carbon dioxide, which then returns to the atmosphere.

Carbon is continuously moving through the biosphere.

Nitrogen is important for life because it is a major component of genes.

The largest pool of nitrogen in the air is not usable by plants, which are the primary producers.

Azotobacter and the ubiquitous cyanobacteria are found in soil.
Nitrogen fixingbacteria, like Rhizobium, live in the roots of the plant.
nitrification is a process in which different species ofbacteria oxidize the ammonium ion.
The process of nitrification begins with the conversion of ammonium to nitrite.
The genera Nitrosomas, Nitrobacter, and Nitrospira carry out nitrification in soils.
Nitrogen is found in the form of ammonia or nitrate.
Plants can use ammonia and nitrate.

Ammonia makes up 15 percent of the total nitrogen released, but the rest is N2 and N2O.

N2 is the final product of the catabolization of ammonia.
Denitrifyingbacteria reverse the process of nitrification, reducing the nitrate from soils to gaseous compounds such as N2O, NO, and N2.

The nitrogen cycle is influenced by prokaryotes.

2 are converted to NH4