Nutrition is the
biochemical and
physiological process by which an
organism
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
uses
food to support its
life
Life is a quality that distinguishes matter that has biological processes, such as Cell signaling, signaling and self-sustaining processes, from that which does not, and is defined by the capacity for Cell growth, growth, reaction to Stimu ...
. It provides organisms with
nutrients
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excre ...
, which can be
metabolized
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
to create energy and chemical structures. Failure to obtain sufficient nutrients causes
malnutrition
Malnutrition occurs when an organism gets too few or too many nutrients, resulting in health problems. Specifically, it is "a deficiency, excess, or imbalance of energy, protein and other nutrients" which adversely affects the body's tissues ...
.
Nutritional science
Nutritional science (also nutrition science, sometimes short ''nutrition'', dated trophology) is the science that studies the physiological process of nutrition (primarily human nutrition), interpreting the nutrients and other substances in food ...
is the study of nutrition, though it typically emphasizes
human nutrition
Human nutrition deals with the provision of essential nutrients in food that are necessary to support human life and good health. Poor nutrition is a chronic problem often linked to poverty, food security, or a poor understanding of nutritiona ...
.
The type of organism determines what nutrients it needs and how it obtains them. Organisms obtain nutrients by consuming
organic matter, consuming inorganic matter, absorbing light, or some combination of these. Some can produce nutrients internally by consuming basic elements, while some must consume other organisms to obtain preexisting nutrients. All forms of life require
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
,
energy
In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...
, and
water
Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
as well as various other molecules. Animals require complex nutrients such as
carbohydrate
In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or m ...
s,
lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids includ ...
s, and
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
s, obtaining them by consuming other organisms. Humans have developed
agriculture
Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people t ...
and
cooking to replace
foraging
Foraging is searching for wild food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce. Foraging theory is a branch of behavioral ecology that studies the foraging behavi ...
and advance human nutrition. Plants acquire nutrients through
soil
Soil, also commonly referred to as earth or dirt
Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty.
Common types of dirt include:
* Debri ...
and the atmosphere. Fungi absorb nutrients around them by breaking them down and absorbing them through the
mycelium
Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrates. A typical single spore germinates ...
.
Study
Scientific analysis of food and nutrients began during the
chemical revolution
The chemical revolution, also called the ''first chemical revolution'', was the early modern reformulation of chemistry that culminated in the law of conservation of mass and the oxygen theory of combustion.
During the 19th and 20th century, this ...
in the late-18th century. Chemists in the 18th and 19th centuries experimented with different elements and food sources to develop theories of nutrition. Modern nutrition science began in the 1910s as individual micronutrients began to be identified. The first vitamin to be chemically identified was
thiamine
Thiamine, also known as thiamin and vitamin B1, is a vitamin, an essential micronutrient, that cannot be made in the body. It is found in food and commercially synthesized to be a dietary supplement or medication. Phosphorylated forms of thi ...
in 1926, and the role of vitamins in nutrition was studied in the following decades. The first recommended dietary allowances for humans were developed during the
Great Depression and
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
. Due to its importance in human health, the study of nutrition has heavily emphasized human nutrition and agriculture, while
ecology
Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overl ...
is a secondary concern.
Nutrients
Nutrients are substances that provide energy and physical components to the organism, allowing it to survive, grow, and reproduce. Nutrients can be basic elements or complex
macromolecules. Approximately 30 elements are found in
organic matter, with
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
,
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
, and
phosphorus
Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
being the most important.
Macronutrient
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excre ...
s are the primary substances required by an organism, and
micronutrients are substances required by an organism in trace amounts. Organic micronutrients are classified as
vitamin
A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrie ...
s, and inorganic micronutrients are classified as
minerals
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed ...
.
Nutrients are absorbed by the cells and used in metabolic biochemical reactions. These include fueling reactions that create precursor
metabolites and energy, biosynthetic reactions that convert precursor metabolites into building block molecules,
polymerization
In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many fo ...
s that combine these molecules into macromolecule
polymer
A polymer (; Greek '' poly-'', "many" + ''-mer'', "part")
is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
s, and assembly reactions that use these polymers to construct cellular structures.
Nutritional groups
Organisms can be classified by how they obtain carbon and energy.
Heterotroph
A heterotroph (; ) 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 ...
s are organisms that obtain nutrients by consuming the carbon of other organisms, while
autotroph
An autotroph or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide,Morris, J. et al. (2019). "Biology: How Life Wo ...
s are organisms that produce their own nutrients from the carbon of inorganic substances like
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
.
Mixotroph A mixotroph is an organism that can use a mix of different sources of energy and carbon, instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other. It is estimated that mixotrophs comp ...
s are organisms that can be heterotrophs and autotrophs, including some
plankton
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
and
carnivorous plant
Carnivorous plants are plants that derive some or most of their nutrients from trapping and consuming animals or protozoans
Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryot ...
s.
Phototroph
Phototrophs () are organisms that carry out photon capture to produce complex organic compounds (e.g. carbohydrates) and acquire energy. They use the energy from light to carry out various cellular metabolic processes. It is a common misconcep ...
s obtain energy from light, while
chemotroph
A Chemotroph is an organism that obtains energy by the oxidation of electron donors in their environments. These molecules can be organic ( chemoorganotrophs) or inorganic (chemolithotrophs). The chemotroph designation is in contrast to phototro ...
s obtain energy by consuming chemical energy from matter.
Organotroph
An organotroph is an organism that obtains hydrogen or electrons from organic substrates. This term is used in microbiology to classify and describe organisms based on how they obtain electrons for their respiration processes. Some organotrophs su ...
s consume other organisms to obtain electrons, while
lithotroph
Lithotrophs are a diverse group of organisms using an inorganic substrate (usually of mineral origin) to obtain reducing equivalents for use in biosynthesis (e.g., carbon dioxide fixation) or energy conservation (i.e., ATP production) via aerobic ...
s obtain electrons from inorganic substances, such as
water
Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
,
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
,
dihydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, and ...
,
iron(II)
In chemistry, iron(II) refers to the element iron in its +2 oxidation state. In ionic compounds (salts), such an atom may occur as a separate cation (positive ion) denoted by Fe2+.
The adjective ferrous or the prefix ferro- is often used to spe ...
,
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
, or
ammonium
The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary a ...
. Prototrophs can create essential nutrients from other compounds, while
auxotroph
Auxotrophy ( grc, αὐξάνω "to increase"; ''τροφή'' "nourishment") is the inability of an organism to synthesize a particular organic compound required for its growth (as defined by IUPAC). An auxotroph is an organism that displays this ...
s must consume preexisting nutrients.
Diet
In nutrition, the
diet
Diet may refer to:
Food
* Diet (nutrition), the sum of the food consumed by an organism or group
* Dieting, the deliberate selection of food to control body weight or nutrient intake
** Diet food, foods that aid in creating a diet for weight loss ...
of an organism is the sum of foods it eats.
Nutrient cycle
A
nutrient cycle
A nutrient cycle (or ecological recycling) is the movement and exchange of inorganic and organic matter back into the production of matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of mineral nutrients is cycli ...
is a
biogeochemical cycle
A biogeochemical cycle (or more generally a cycle of matter) is the pathway by which a chemical substance cycles (is turned over or moves through) the biotic and the abiotic compartments of Earth. The biotic compartment is the biosphere and the ...
involving the movement of inorganic matter through a combination of soil, organisms, air or water, where they are exchanged in organic matter.
[ ] Energy flow is a unidirectional and noncyclic pathway, whereas the movement of
mineral nutrients
In the context of nutrition, a mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life. However, the four major structural elements in the human body by weight (oxygen, hydrogen, carbon, ...
is cyclic. Mineral cycles include the
carbon cycle
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and Earth's atmosphere, atmosphere of the Earth. Carbon is the main component of biological compounds as well as ...
,
sulfur cycle
The sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element ( CHNOPS), being a const ...
,
nitrogen cycle
The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biologi ...
,
water cycle
The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly cons ...
,
phosphorus cycle
The phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the Earth's atmosphere, atmosphere does not play a significan ...
,
oxygen cycle
Oxygen cycle refers to the movement of oxygen through the atmosphere (air), biosphere (plants and animals) and the lithosphere (the Earth’s crust). The oxygen cycle demonstrates how free oxygen is made available in each of these regions, as wel ...
, among others that continually recycle along with other mineral nutrients into
productive
Productivity is the efficiency of production of goods or services expressed by some measure. Measurements of productivity are often expressed as a ratio of an aggregate output to a single input or an aggregate input used in a production proces ...
ecological nutrition.
Biogeochemical cycles
A biogeochemical cycle (or more generally a cycle of matter) is the pathway by which a chemical substance cycles (is turned over or moves through) the biotic and the abiotic compartments of Earth. The biotic compartment is the biosphere and the ...
that are performed by living organisms and natural processes are
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
,
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
,
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
,
phosphorus
Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
, and
sulfur cycles.
Foraging
![BonoboFishing04](https://upload.wikimedia.org/wikipedia/commons/3/3b/BonoboFishing04.jpeg)
Foraging is the process of seeking out nutrients in the environment. It may also be defined to include the subsequent use of the resources. Some organisms, such as animals and bacteria, can navigate to find nutrients, while others, such as plants and fungi, extend outward to find nutrients. Foraging may be random, in which the organism seeks nutrients without method, or it may be systematic, in which the organism can go directly to a food source. Organisms are able to detect nutrients through
taste
The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ...
or other forms of
nutrient sensing Nutrient sensing is a cell's ability to recognize and respond to fuel substrates such as glucose. Each type of fuel used by the cell requires an alternate pathway of utilization and accessory molecules. In order to conserve resources a cell will o ...
, allowing them to regulate nutrient intake.
Optimal foraging theory
Optimal foraging theory (OFT) is a behavioral ecology model that helps predict how an animal behaves when searching for food. Although obtaining food provides the animal with energy, searching for and capturing the food require both energy and t ...
is a model that explains foraging behavior as a
cost–benefit analysis
Cost–benefit analysis (CBA), sometimes also called benefit–cost analysis, is a systematic approach to estimating the strengths and weaknesses of alternatives. It is used to determine options which provide the best approach to achieving benefits ...
in which an animal must maximize the gain of nutrients while minimizing the amount of time and energy spent foraging. It was created to analyze the foraging habits of animals, but it can also be extended to other organisms. Some organisms are specialists that are adapted to forage for a single food source, while others are generalists that can consume a variety of food sources.
Nutrient deficiency
Nutrient deficiencies, known as
malnutrition
Malnutrition occurs when an organism gets too few or too many nutrients, resulting in health problems. Specifically, it is "a deficiency, excess, or imbalance of energy, protein and other nutrients" which adversely affects the body's tissues ...
, occur when an organism does not have the nutrients that it needs. This may be caused by absorbing insufficient nutrients or by suddenly losing nutrients. When this occurs, an organism will adapt by reducing energy consumption and expenditure to prolong the use of stored nutrients. It will use stored energy reserves until they are depleted, and it will then break down its own body mass for additional energy.
In organisms
Animal
![Kingfisher eating a tadpole](https://upload.wikimedia.org/wikipedia/commons/b/b3/Kingfisher_eating_a_tadpole.jpg)
Animals are heterotrophs that consume other organisms to obtain nutrients.
Herbivore
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
s are animals that eat plants,
carnivore
A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...
s are animals that eat other animals, and
omnivore
An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutr ...
s are animals that eat both plants and other animals. Many herbivores rely on bacterial fermentation to create digestible nutrients from indigestible plant cellulose, while obligate carnivores must eat animal meats to obtain certain vitamins or nutrients their bodies cannot otherwise synthesize. Animals generally have a higher requirement of energy in comparison to plants. The macronutrients essential to animal life are carbohydrates,
amino acids
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...
, and
fatty acids
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...
.
All macronutrients except water are required by the body for energy, however, this is not their sole physiological function. The energy provided by macronutrients in food is measured in kilocalories, usually called Calories, where 1 Calorie is the amount of energy required to raise 1 kilogram of water by 1 degree Celsius.
Carbohydrates are molecules that store significant amounts of energy. Animals digest and metabolize carbohydrates to obtain this energy. Carbohydrates are typically synthesized by plants during metabolism, and animals have to obtain most carbohydrates from nature, as they have only a limited ability to generate them. They include
sugar
Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double ...
s,
oligosaccharide
An oligosaccharide (/ˌɑlɪgoʊˈsækəˌɹaɪd/; from the Greek ὀλίγος ''olígos'', "a few", and σάκχαρ ''sácchar'', "sugar") is a saccharide polymer containing a small number (typically two to ten) of monosaccharides (simple sugar ...
s, and
polysaccharide
Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wa ...
s.
Glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
is the simplest form of carbohydrate. Carbohydrates are broken down to produce glucose and
short-chain fatty acid Short-chain fatty acids (SCFAs) are fatty acids with fewer than six carbon atoms. Derived from intestinal microbial fermentation of indigestible foods, SCFAs are the main energy source of colonocytes, making them crucial to gastrointestinal health. ...
s, and they are the most abundant nutrients for herbivorous land animals.
Lipids provide animals with fats and oils. They are not soluble in water, and they can store energy for an extended period of time. They can be obtained from many different plant and animal sources. Most dietary lipids are
triglyceride
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as w ...
s, composed of
glycerol
Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
and fatty acids.
Phospholipid
Phospholipids, are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typ ...
s and
sterol
Sterol is an organic compound with formula , whose molecule is derived from that of gonane by replacement of a hydrogen atom in position 3 by a hydroxyl group. It is therefore an alcohol of gonane. More generally, any compounds that contain the go ...
s are found in smaller amounts. An animal's body will reduce the amount of fatty acids it produces as dietary fat intake increases, while it increases the amount of fatty acids it produces as carbohydrate intake increases.
Protein consumed by animals is broken down to amino acids, which would be later used to synthesize new proteins. Protein is used to form cellular structures, fluids, and
enzymes
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...
(biological
catalysts
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
). Enzymes are essential to most
metabolic
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
processes, as well as
DNA replication
In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all living organisms acting as the most essential part for biological inheritanc ...
,
repair
The technical meaning of maintenance involves functional checks, servicing, repairing or replacing of necessary devices, equipment, machinery, building infrastructure, and supporting utilities in industrial, business, and residential installa ...
, and
transcription
Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including:
Genetics
* Transcription (biology), the copying of DNA into RNA, the fir ...
.
Much of
animal behavior
Ethology is the scientific study of animal behaviour, usually with a focus on behaviour under natural conditions, and viewing behaviour as an evolutionarily adaptive trait. Behaviourism as a term also describes the scientific and objective ...
is governed by nutrition.
Migration patterns and
seasonal breeding take place in conjunction with food availability, and
courtship display
A courtship display is a set of display behaviors in which an animal, usually a male, attempts to attract a mate; the mate exercises choice, so sexual selection acts on the display. These behaviors often include ritualized movement ("dances"), ...
s are used to display an animal's health. Animals develop positive and negative associations with foods that affect their health, and they can instinctively avoid foods that have caused
toxic injury
A toxic injury is a type of injury caused by toxin. Toxic injuries can cause teratogenic effects, respiratory effects, gastrointestinal effects, cardiovascular effects, hepatic effects, renal effects and neurological effects. They can also lead to ...
or nutritional imbalances through a
conditioned food aversion
Poison shyness, also called conditioned food aversion, refers to the avoidance of a toxic substance by an animal that has previously ingested that substance. Animals learn an association between stimulus characteristics, usually the taste or odor, ...
. Some animals, such as rats, do not seek out new types of foods unless they have a nutrient deficiency.
Human
![Brazilian Gourmet, Fitzrovia, London (5990236962)](https://upload.wikimedia.org/wikipedia/commons/a/a6/Brazilian_Gourmet%2C_Fitzrovia%2C_London_%285990236962%29.jpg)
Early human nutrition consisted of foraging for nutrients similar to that of other animals, but it diverged at the beginning of the
Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...
with the
Neolithic Revolution
The Neolithic Revolution, or the (First) Agricultural Revolution, was the wide-scale transition of many human cultures during the Neolithic period from a lifestyle of hunting and gathering to one of agriculture and settlement, making an incre ...
, in which humans developed agriculture to produce food. The Chemical Revolution in the 18th century allowed humans to study the nutrients in foods and develop more advanced methods of
food preparation
Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is inge ...
. Major advances in economics and technology during the 20th century allowed
mass production
Mass production, also known as flow production or continuous production, is the production of substantial amounts of standardized products in a constant flow, including and especially on assembly lines. Together with job production and batch ...
and
food fortification
Food fortification or enrichment is the process of adding micronutrients (essential trace elements and vitamins) to food. It can be carried out by food manufacturers, or by governments as a public health policy which aims to reduce the number of p ...
to better meet the nutritional needs of humans.
Human behavior
Human behavior is the potential and expressed capacity ( mentally, physically, and socially) of human individuals or groups to respond to internal and external stimuli throughout their life. Kagan, Jerome, Marc H. Bornstein, and Richard M. L ...
is closely related to human nutrition, making it a subject of
social science
Social science is one of the branches of science, devoted to the study of societies and the relationships among individuals within those societies. The term was formerly used to refer to the field of sociology, the original "science of soc ...
in addition to biology. Nutrition in humans is balanced with eating for pleasure, and optimal diet may vary depending on the demographics and health concerns of each person.
Humans are omnivores that eat a variety of foods. Cultivation of
cereal
A cereal is any Poaceae, grass cultivated for the edible components of its grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, Cereal germ, germ, and bran. Cereal Grain, grain crops are grown in greater quantit ...
s and production of
bread
Bread is a staple food prepared from a dough of flour (usually wheat) and water, usually by baking. Throughout recorded history and around the world, it has been an important part of many cultures' diet. It is one of the oldest human-made f ...
has made up a key component of human nutrition since the beginning of agriculture. Early humans hunted animals for meat, and modern humans domesticate animals to consume their meat and eggs. The development of
animal husbandry
Animal husbandry is the branch of agriculture concerned with animals that are raised for meat, fibre, milk, or other products. It includes day-to-day care, selective breeding, and the raising of livestock. Husbandry has a long history, starti ...
has also allowed humans in some cultures to consume the
milk
Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digestion, digest solid food. Immune factors and immune ...
of other animals and produce it into foods such as
cheese
Cheese is a dairy product produced in wide ranges of flavors, textures, and forms by coagulation of the milk protein casein. It comprises proteins and fat from milk, usually the milk of cows, buffalo, goats, or sheep. During production, ...
. Other foods eaten by humans include nuts, seeds, fruits, and vegetables. Access to domesticated animals as well as
vegetable oil
Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. Like animal fats, vegetable fats are ''mixtures'' of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or fat ...
s has caused a significant increase in human intake of fats and oils. Humans have developed advanced methods of
food processing
Food processing is the transformation of agricultural products into food, or of one form of food into other forms. Food processing includes many forms of processing foods, from grinding grain to make raw flour to home cooking to complex industr ...
that prevents contamination of pathogenic microorganisms and simplify the production of food. These include drying, freezing, heating, milling, pressing, packaging, refrigeration, and irradiation. Most cultures add
herb
In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables and other plants consumed for macronutrients, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal ...
s and
spice
A spice is a seed, fruit, root, bark, or other plant substance primarily used for flavoring or coloring food. Spices are distinguished from herbs, which are the leaves, flowers, or stems of plants used for flavoring or as a garnish. Spices a ...
s to foods before eating to add flavor, though most do not significantly affect nutrition. Other additives are also used to improve the safety, quality, flavor, and nutritional content of food.
Humans obtain most carbohydrates as starch from cereals, though sugar has grown in importance. Lipids can be found in
animal fat
Animal fats and oils are lipids derived from animals: oils are liquid at room temperature, and fats are solid. Chemically, both fats and oils are composed of triglycerides. Although many animal parts and secretions may yield oil, in commercial p ...
,
butterfat
Butterfat or milkfat is the fatty portion of milk. Milk and cream are often sold according to the amount of butterfat they contain.
Composition
Butterfat is mainly composed of triglycerides. Each triglyceride contains three fatty acids. Butt ...
, vegetable oil, and
leaf vegetable
Leaf vegetables, also called leafy greens, pot herbs, vegetable greens, or simply greens, are plant leaves eaten as a vegetable, sometimes accompanied by tender petioles and shoots. Leaf vegetables eaten raw in a salad can be called salad gre ...
s, and they are also used to increase flavor in foods. Protein can be found in virtually all foods, as it makes up cellular material, though certain methods of food processing may reduce the amount of protein in a food. Humans can also obtain energy from
ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
, which is both a food and a drug, but it provides relatively few essential nutrients and is associated with nutritional deficiencies and other health risks.
In humans, poor nutrition can cause deficiency-related diseases such as
blindness
Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment ...
,
anemia
Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen due to a lower than normal number of red blood cells, or a reduction in the amount of hemoglobin. When anemia comes on slowly, th ...
,
scurvy
Scurvy is a disease resulting from a lack of vitamin C (ascorbic acid). Early symptoms of deficiency include weakness, feeling tired and sore arms and legs. Without treatment, decreased red blood cells, gum disease, changes to hair, and bleeding ...
,
preterm birth
Preterm birth, also known as premature birth, is the Childbirth, birth of a baby at fewer than 37 weeks Gestational age (obstetrics), gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 we ...
,
stillbirth
Stillbirth is typically defined as fetal death at or after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without signs of life. A stillbirth can result in the feeling of guilt or grief in the mother. The term ...
and
cretinism
Congenital iodine deficiency syndrome is a medical condition present at birth marked by impaired physical and mental development, due to insufficient thyroid hormone (hypothyroidism) often caused by insufficient dietary iodine during pregnancy. It ...
,
or nutrient excess health-threatening conditions such as
obesity
Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's we ...
and
metabolic syndrome
Metabolic syndrome is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL).
Metabolic syndrome ...
; and such common chronic systemic diseases as
cardiovascular disease
Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, h ...
,
diabetes
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
, and
osteoporosis
Osteoporosis is a systemic skeletal disorder characterized by low bone mass, micro-architectural deterioration of bone tissue leading to bone fragility, and consequent increase in fracture risk. It is the most common reason for a broken bone ...
. Undernutrition can lead to
wasting
In medicine, wasting, also known as wasting syndrome, refers to the process by which a debilitating disease causes muscle and fat tissue to "waste" away. Wasting is sometimes referred to as "acute malnutrition" because it is believed that episo ...
in acute cases, and
stunting of
marasmus
Marasmus is a form of severe malnutrition characterized by energy deficiency. It can occur in anyone with severe malnutrition but usually occurs in children. Body weight is reduced to less than 62% of the normal (expected) body weight for the a ...
in chronic cases of malnutrition.
Domesticated animal
In
domesticated animals
This page gives a list of domesticated animals, also including a list of animals which are or may be currently undergoing the process of domestication and animals that have an extensive relationship with humans beyond simple predation. This includ ...
, such as
pets
A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive appearances, intelligence, ...
,
livestock
Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to animals ...
, and
working animals
A working animal is an animal, usually domesticated, that is kept by humans and trained to perform tasks instead of being slaughtered to harvest animal products. Some are used for their physical strength (e.g. oxen and draft horses) or for tr ...
, as well as other
animals in captivity
Animals that are held by humans and prevented from escaping are said to be in captivity. The term is usually applied to wild animals that are held in confinement, but may also be used generally to describe the keeping of domesticated animals suc ...
, nutrition is managed by humans through
animal feed
Animal feed is food given to domestic animals, especially livestock, in the course of animal husbandry. There are two basic types: fodder and forage. Used alone, the word ''feed'' more often refers to fodder. Animal feed is an important input to ...
.
Fodder
Fodder (), also called provender (), is any agriculture, agricultural foodstuff used specifically to feed domesticated livestock, such as cattle, domestic rabbit, rabbits, sheep, horses, chickens and pigs. "Fodder" refers particularly to food g ...
and
forage
Forage is a plant material (mainly plant leaves and stems) eaten by grazing livestock. Historically, the term ''forage'' has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used m ...
are provided to livestock. Specialized
pet food
Pet food is animal feed intended for consumption by pets. Typically sold in pet stores and supermarkets, it is usually specific to the type of animal, such as dog food or cat food. Most meat used for animals is a byproduct of the human food indu ...
has been manufactured since 1860, and subsequent research and development have addressed the nutritional needs of pets.
Dog food
Dog food is food specifically formulated and intended for consumption by dogs and other related canines. Dogs are considered to be omnivores with a carnivorous bias. They have the sharp, pointed teeth and shorter gastrointestinal tracts of ca ...
and
cat food in particular are heavily studied and typically include all essential nutrients for these animals. Cats are sensitive to some common nutrients, such as
taurine
Taurine (), or 2-aminoethanesulfonic acid, is an organic compound that is widely distributed in animal tissues. It is a major constituent of bile and can be found in the large intestine, and accounts for up to 0.1% of total human body weight. It ...
, and require additional nutrients derived from meat. Large-breed puppies are susceptible to overnutrition, as small-breed dog food is more energy dense than they can absorb.
Plant
![Photosynthesis_en](https://upload.wikimedia.org/wikipedia/commons/5/55/Photosynthesis_en.svg)
Most plants obtain nutrients through inorganic substances
absorbed from the soil or the atmosphere. Carbon, hydrogen, oxygen, nitrogen, and sulfur are essential nutrients that make up organic material in a plant and allow enzymic processes. These are absorbed ions in the soil, such as
bicarbonate
In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula .
Bicarbonate serves a crucial biochemic ...
,
nitrate
Nitrate is a polyatomic ion
A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
,
ammonium
The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary a ...
, and
sulfate
The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ar ...
, or they are absorbed as gases, such as carbon dioxide, water, oxygen gas, and
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
. Phosphorus, boron, and silicon are used for
esterification
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...
. They are obtained through the soil as
phosphate
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid .
The phosphate or orthophosphate ion is derived from phospho ...
s,
boric acid
Boric acid, more specifically orthoboric acid, is a compound of boron, oxygen, and hydrogen with formula . It may also be called hydrogen borate or boracic acid. It is usually encountered as colorless crystals or a white powder, that dissolves ...
, and
silicic acid
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...
, respectively. Other nutrients used by plants are potassium, sodium, calcium, magnesium, manganese, chlorine, iron, copper, zinc, and molybdenum.
Plants uptake essential elements from the soil through their
root
In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the sur ...
s and from the air (consisting of mainly nitrogen and oxygen) through their
leaves
A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
. Nutrient uptake in the soil is achieved by
cation exchange
Ion exchange is a reversible interchange of one kind of ion present in an insoluble solid with another of like charge present in a solution surrounding the solid with the reaction being used especially for softening or making water demineralised, ...
, wherein
root hair
Root hair, or absorbent hairs, are outgrowths of epidermal cells, specialized cells at the tip of a plant root. They are lateral extensions of a single cell and are only rarely branched. They are found in the region of maturation, of the root. Root ...
s pump
hydrogen ion
A hydrogen ion is created when a hydrogen atom loses or gains an electron. A positively charged hydrogen ion (or proton) can readily combine with other particles and therefore is only seen isolated when it is in a gaseous state or a nearly particle ...
s (H
+) into the soil through
proton pump
A proton pump is an integral membrane protein pump that builds up a proton gradient across a biological membrane. Proton pumps catalyze the following reaction:
: n one side of a biological membrane/sub> + energy n the other side of the membr ...
s. These hydrogen ions displace
cation
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
s attached to negatively charged soil particles so that the cations are available for uptake by the root. In the leaves,
stomata
In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...
open to take in carbon dioxide and expel
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
. Although
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
is plentiful in the Earth's atmosphere, very few plants can use this directly. Most plants, therefore, require nitrogen compounds to be present in the soil in which they grow. This is made possible by the fact that largely inert atmospheric nitrogen is changed in a
nitrogen fixation
Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmo ...
process to biologically usable forms in the soil by bacteria.
As these nutrients do not provide the plant with energy, they must obtain energy by other means.
Green plants absorb energy from
sunlight
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...
with
chloroplasts
A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, ...
and convert it to usable energy through
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
.
Fungus
Fungi are chemoheterotrophs that consume external matter for energy. Most fungi absorb matter through the root-like mycelium, which grows through the organism's source of nutrients and can extend indefinitely. The fungus excretes
extracellular enzymes
Extracellular enzymes or exoenzymes are synthesized inside the cell and then secreted outside the cell, where their function is to break down complex macromolecules into smaller units to be taken up by the cell for growth and assimilation. These ...
to break down surrounding matter and then absorbs the nutrients through the cell wall. Fungi can be parasitic, saprophytic, or symbiotic. Parasitic fungi attach and feed on living hosts, such as animals, plants, or other fungi. Saprophytic fungi feed on dead and decomposing organisms. Symbiotic fungi grow around other organisms and exchange nutrients with them.
Protist
Protists
A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the excl ...
include all
eukaryotes
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
that are not animals, plants, or fungi, resulting in great diversity between them.
Algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
are photosynthetic protists that can produce energy from light. Several types of protists use mycelium similar to those of fungi.
Protozoa
Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...
are heterotrophic protists, and different protozoa seek nutrients in different ways.
Flagellate
A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and their ...
protozoa use a
flagellum
A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates.
A microorganism may have f ...
to assist in hunting for food, and some protozoa travel via infectious spores to act as parasites. Many protists are mixotrophic, having both phototrophic and heterotrophic characteristics. Mixotrophic protists will typically depend on one source of nutrients while using the other as a supplemental source or a temporary alternative when its primary source is unavailable.
Prokaryote
Prokaryote
A prokaryote () is a single-celled organism that lacks a nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Greek πρό (, 'before') and κάρυον (, 'nut' or 'kernel').Campbell, N. "Biology:Concepts & Connec ...
s, including
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
and
archaea
Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...
, vary greatly in how they obtain nutrients across nutritional groups. Prokaryotes can only transport soluble compounds across their cell envelopes, but they can break down chemical components around them. Some lithotrophic prokaryotes are
extremophile
An extremophile (from Latin ' meaning "extreme" and Greek ' () meaning "love") is an organism that is able to live (or in some cases thrive) in extreme environments, i.e. environments that make survival challenging such as due to extreme temper ...
s that can survive in nutrient-deprived environments by breaking down inorganic matter. Phototrophic prokaryotes, such as
cyanobacteria
Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...
and
Chloroflexia
The Chloroflexia are a class of bacteria in the phylum
In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of p ...
, can engage in photosynthesis to obtain energy from sunlight. This is common among bacteria that form in mats atop geothermal springs. Phototrophic prokaryotes typically obtain carbon from assimilating carbon dioxide through the
Calvin cycle
The Calvin cycle, light-independent reactions, bio synthetic phase, dark reactions, or photosynthetic carbon reduction (PCR) cycle of photosynthesis is a series of chemical reactions that convert carbon dioxide and hydrogen-carrier compounds into ...
.
Some prokaryotes, such as ''
Bdellovibrio'' and
''Ensifer'', are predatory and feed on other single-celled organisms. Predatory prokaryotes seek out other organisms through
chemotaxis
Chemotaxis (from '' chemo-'' + ''taxis'') is the movement of an organism or entity in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemica ...
or random collision, merge with the organism, degrade it, and absorb the released nutrients. Predatory strategies of prokaryotes include attaching to the outer surface of the organism and degrading it externally, entering the cytoplasm of the organism, or by entering the
periplasmic space
The periplasm is a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the ''periplasmic space'' in gram-negative bacteria. Using cryo-electron microscopy it has been found that ...
of the organism. Groups of predatory prokaryotes may forgo attachment by collectively producing
hydrolytic
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysi ...
enzymes.
See also
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References
Bibliography
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External links
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