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Biochemistry or biological chemistry, is the study of
chemical process In a scientific Science () is a systematic enterprise that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe."... modern science is a discovery as well ...
es within and relating to living
organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological me ...

organism
s. A sub-discipline of both
chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during a with other . ...

chemistry
and
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Development ...

biology
, biochemistry may be divided into three fields: structural biology,
enzymology Enzymes () are protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme ...
and
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities that have biological processes, such as Cell signaling, signaling and self-sustaining ...

metabolism
. Over the last decades of the 20th century, biochemistry has become successful at explaining living processes through these three disciplines. Almost all areas of the life sciences are being uncovered and developed through biochemical methodology and research.
VoetVoet is the surname of: *Alexander Voet the Elder (1608-1689), Flemish printmaker and publisher *Alexander Voet the Younger (1637–1693/1705), Flemish printmaker and publisher *Donald Voet, American biochemist and textbook author *Gijsbert Voet (15 ...
(2005), p. 3.
Biochemistry focuses on understanding the chemical basis which allows biological molecules to give rise to the processes that occur within living
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious recluse lives * Prison cell, a room used to hold peopl ...
and between cells,
Karp Karp may refer to: Places * Karp, Podlaskie Voivodeship, in north-east Poland * Karp, Lublin Voivodeship, in east Poland People * Karp (surname) * Karp Khachvankyan (1923–1998), Armenian actor and director Other uses * KARP-FM, a radio station ...
(2009), p. 2.
in turn relating greatly to the understanding of tissues and
organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly categorized as parenchyma Parenchyma () is the bulk of functional ...
, as well as organism structure and function.
Miller A miller is a person who operates a mill Mill may refer to: Science and technology * Mill (grinding) * Milling (machining) * List of types of mill * Mill, the arithmetic unit of the Analytical Engine early computer * Textile manufacturing, Texti ...
(2012). p. 62.
Biochemistry is closely related to
molecular biology Molecular biology is the branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, molecular synthesis, modification, mechanisms, and interaction ...
which is the study of the
molecular A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atom An atom is the smallest unit of ordinary matter In ...

molecular
mechanisms of biological phenomena.
AstburyAstbury is a surname. Notable people with the surname include: * Andrew Astbury, English swimmer *Ian Astbury Ian Robert Astbury (born 14 May 1962) is a British singer and songwriter. He is best known as a founding member and lead vocalist for t ...
(1961), p. 1124.
Much of biochemistry deals with the structures, functions, and interactions of biological
macromolecule macromolecule A macromolecule is a very large molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neu ...
s, such as
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
s,
nucleic acid Nucleic acids are biopolymers, macromolecules, essential to all Organism, known forms of life. They are composed of nucleotides, which are the monomers made of three components: a pentose, 5-carbon sugar, a phosphate group and a nitrogenous base. ...

nucleic acid
s,
carbohydrate is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are simple sugars soluble in water. Three common ex ...
s, and
lipid In and , a lipid is a macro that is soluble in solvents. are typically s used to dissolve other naturally occurring hydrocarbon lipid s that do not (or do not easily) dissolve in water, including s, es, s, fat-soluble s (such as vitamins A, ...
s. They provide the structure of cells and perform many of the functions associated with life.
Eldra ''Eldra'' is a 2003 British drama film directed by Timothy Lyn. It was selected as the British entry for the Academy Award for Best Foreign Language Film, Best Foreign Language Film at the 75th Academy Awards, but it was not nominated. Cast * Io ...
(2007), p. 45.
The chemistry of the cell also depends upon the reactions of small
molecule A molecule is an electrically Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position In physics, motion is the phenomenon ...

molecule
s and
ion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ...
s. These can be
inorganic In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they under ...
(for example,
water Water (chemical formula H2O) 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 li ...

water
and
metal A metal (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appro ...

metal
ions) or
organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or ...
(for example, the
amino acid Amino acids are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, a ...

amino acid
s, which are used to synthesize proteins).
Marks Marks may refer to: Business * Mark's, a Canadian retail chain * Marks & Spencer, a British retail chain * Collective trade marks, trademarks owned by an organisation for the benefit of its members * Marks & Co, the inspiration for the novel ''8 ...
(2012), Chapter 14.
The mechanisms used by cells to harness energy from their environment via
chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and t ...

chemical reaction
s are known as
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities that have biological processes, such as Cell signaling, signaling and self-sustaining ...

metabolism
. The findings of biochemistry are applied primarily in
medicine Medicine is the science Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity, awareness, or understanding of someone or something, such as facts ( descriptive knowledge), skills (proced ...

medicine
,
nutrition Nutrition is the biochemical Biochemistry or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: st ...
and
agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise trends, Increases in sedentary behaviors su ...

agriculture
. In medicine, biochemists investigate the causes and cures of
disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interactin ...
s. Nutrition studies how to maintain health and wellness and also the effects of
nutritional deficiencies Malnutrition is a condition that results from eating a diet which does not supply a healthy amount of one or more nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient in ...
.
UNICEF UNICEF, also known as the United Nations Children's Fund, is a United Nations The United Nations (UN) is an intergovernmental organization that aims to maintain international peace and international security, security, develop friendly ...
(2010), pp. 61, 75.
In agriculture, biochemists investigate
soil Soil is a mixture In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, comp ...

soil
and
fertilizer A fertilizer (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American E ...

fertilizer
s. Improving crop cultivation, crop storage, and
pest control Pest control is the regulation or management of a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often def ...
are also goals.


History

At its most comprehensive definition, biochemistry can be seen as a study of the components and composition of living things and how they come together to become life. In this sense, the history of biochemistry may therefore go back as far as the
ancient Greeks Ancient Greece ( el, Ἑλλάς, Hellás) was a civilization belonging to a period of History of Greece, Greek history from the Greek Dark Ages of the 12th–9th centuries BC to the end of Classical Antiquity, antiquity ( AD 600). This era was ...
. Helvoort (2000), p. 81. However, biochemistry as a specific
scientific discipline The branches of science, also referred to as science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes knowledge in the form of Tes ...
began sometime in the 19th century, or a little earlier, depending on which aspect of biochemistry is being focused on. Some argued that the beginning of biochemistry may have been the discovery of the first
enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates in ...

enzyme
,
diastase A diastase (; from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxim ...
(now called
amylase An amylase () is an enzyme Enzymes () are protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions within organisms, including , , , providing and , and from one lo ...
), in 1833 by
Anselme Payen Anselme Payen (; 6 January 1795 – 12 May 1871) was a French chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a scientist A scientist is a person who conducts Scientific m ...

Anselme Payen
, while others considered
Eduard Buchner Eduard Buchner (20 May 1860 – 13 August 1917) was a German chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a scientist A scientist is a person who conducts Scientific meth ...
's first demonstration of a complex biochemical process
alcoholic fermentation
alcoholic fermentation
in cell-free extracts in 1897 to be the birth of biochemistry. Some might also point as its beginning to the influential 1842 work by
Justus von Liebig Justus Freiherr (; male, abbreviated as ), (; his wife, abbreviated as , literally "free lord" or "free lady") and (, his unmarried daughters and maiden aunts) are designations used as titles of nobility Traditional rank amongst Euro ...

Justus von Liebig
, ''Animal chemistry, or, Organic chemistry in its applications to physiology and pathology'', which presented a chemical theory of metabolism, or even earlier to the 18th century studies on
fermentation Fermentation is a metabolism, metabolic process that produces chemical changes in organic Substrate (chemistry), substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in ...

fermentation
and
respiration Respiration may refer to: Biology * Cellular respiration, the process in which nutrients are converted into useful energy in a cell ** Anaerobic respiration, cellular respiration without oxygen ** Maintenance respiration, the amount of cellular ...

respiration
by
Antoine Lavoisier Antoine-Laurent de Lavoisier ( , ,; 26 August 17438 May 1794), When reduced without charcoal, it gave off an air which supported respiration and combustion in an enhanced way. He concluded that this was just a pure form of common air and th ...

Antoine Lavoisier
. Many other pioneers in the field who helped to uncover the layers of complexity of biochemistry have been proclaimed founders of modern biochemistry.
Emil Fischer Hermann Emil Louis Fischer FRS FRSE FCS (c; ; 9 October 185215 July 1919) was a German chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a scientist A scientist is a person ...

Emil Fischer
, who studied the chemistry of proteins, and , who studied enzymes and the dynamic nature of biochemistry, represent two examples of early biochemists. The term "biochemistry" itself is derived from a combination of
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Development ...

biology
and
chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during a with other . ...

chemistry
. In 1877,
Felix Hoppe-Seyler Ernst Felix Immanuel Hoppe-Seyler (''né'' Felix Hoppe; 26 December 1825 – 10 August 1895) was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ...

Felix Hoppe-Seyler
used the term (''biochemie'' in German) as a synonym for
physiological chemistry Biochemistry or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...
in the foreword to the first issue of '' Zeitschrift für Physiologische Chemie'' (Journal of Physiological Chemistry) where he argued for the setting up of institutes dedicated to this field of study. The German
chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin Medieval Latin was the form of Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European l ...

chemist
Carl Neuberg Carl Alexander Neuberg (29 July 1877 – 30 May 1956) was an early pioneer in biochemistry Biochemistry or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry an ...

Carl Neuberg
however is often cited to have coined the word in 1903, Ben-Menahem (2009), p. 2982. while some credited it to
Franz Hofmeister Franz Hofmeister (30 August 1850, Prague – 26 July 1922, Würzburg Würzburg (; Main-Franconian: ; bar, Wiazbuag or ) is a List of cities and towns in Germany, city in the traditional region of Franconia in the north of the Germany, German s ...
. It was once generally believed that life and its materials had some essential property or substance (often referred to as the "
vital principle Vitalism is the belief that "living organisms are fundamentally different from non-living entities because they contain some non-physical element or are governed by different principles than are inanimate things". Where vitalism explicitly invoke ...
") distinct from any found in non-living matter, and it was thought that only living beings could produce the molecules of life. Then, in 1828,
Friedrich Wöhler Friedrich Wöhler () FRS(For) HFRSE Fellowship of the Royal Society of Edinburgh (FRSE) is an award granted to individuals that the Royal Society of Edinburgh, Scotland's national academy of science and Literature, letters, judged to be "em ...

Friedrich Wöhler
published a paper on the synthesis of
urea Urea, also known as carbamide, is an organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the prop ...

urea
, proving that
organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or ...
compounds can be created artificially. Kauffman (2001), pp. 121–133. Since then, biochemistry has advanced, especially since the mid-20th century, with the development of new techniques such as
chromatography In chemical analysis, chromatography is a laboratory technique for the Separation process, separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it ...

chromatography
,
X-ray diffraction X-ray crystallography (XRC) is the experimental science determining the atomic and molecular structure of a crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a ...
,
dual polarisation interferometry Dual-polarization interferometry (DPI) is an analytical technique that probes molecular layers adsorbed to the surface of a waveguide using the evanescent wave of a laser beam. It is used to measure the conformational change in proteins, or othe ...
,
NMR spectroscopy Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a technique to observe local magnetic fields around . The sample is placed in a magnetic field and the NMR signal is pr ...
, radioisotopic labeling,
electron microscopy An electron microscope is a microscope A microscope (from grc, μικρός ''mikrós'' 'small' and ''skopeîn'' 'to look (at); examine, inspect') is a laboratory instrument used to examine objects that are too small to be seen by the na ...

electron microscopy
and molecular dynamics simulations. These techniques allowed for the discovery and detailed analysis of many molecules and
metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell (biology), cell. The reactants, products, and intermediates of an enzymatic reaction are known as metabolites, which are modified by a sequence ...
s of the cell, such as
glycolysis Glycolysis is the metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of on ...

glycolysis
and the
Krebs cycle The citric acid cycle (CAC) – also known as the TCA cycle (tricarboxylic acid cycle) or the Krebs cycle – is a series of chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transfor ...
(citric acid cycle), and led to an understanding of biochemistry on a molecular level. Another significant historic event in biochemistry is the discovery of the
gene In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mecha ...

gene
, and its role in the transfer of information in the cell. In the 1950s, James D. Watson,
Francis Crick Francis Harry Compton Crick (8 June 1916 – 28 July 2004) was a British molecular biologist, biophysicist, and neuroscientist A neuroscientist (or neurobiologist) is a scientist A scientist is a person who conducts Scientific method, scie ...

Francis Crick
,
Rosalind Franklin Rosalind Elsie Franklin (25 July 192016 April 1958) was an English chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin Medieval Latin was the form of Latin Latin (, or , ) is a classica ...

Rosalind Franklin
and
Maurice Wilkins Maurice Hugh Frederick Wilkins (15 December 1916 – 5 October 2004) was a New Zealand-born and whose research spanned multiple areas of physics and biophysics, contributing to the scientific understanding of , , and , and to the developme ...
were instrumental in solving DNA structure and suggesting its relationship with the genetic transfer of information. In 1958,
George Beadle George Wells Beadle (October 22, 1903 – June 9, 1989) was an American geneticist. In 1958 he shared one-half of the Nobel Prize in Physiology or Medicine with Edward Tatum for their discovery of the role of genes in regulating biochemical event ...
and
Edward Tatum Edward Lawrie Tatum (December 14, 1909 – November 5, 1975) was an American genetics, geneticist. He shared half of the Nobel Prize in Physiology or Medicine in 1958 with George Beadle for showing that genes control individual steps in metaboli ...
received the
Nobel Prize The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel Alfred Bernhard Nobel ( , ; 21 October 1833 – 10 December 1896) was a Swedish chemist, engineer, inventor, busines ...
for work in fungi showing that one gene produces one enzyme. Krebs (2012), p. 32. In 1988,
Colin Pitchfork Colin Pitchfork (born 23 March 1960) is a British convicted murderer and rapist. He was the first person convicted of murder based on DNA fingerprinting evidence, and the first to be caught as a result of mass DNA screening. Pitchfork rape ...
was the first person convicted of murder with
DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral gro ...

DNA
evidence, which led to the growth of
forensic science Forensic science, also known as criminalistics, is the application of to and , mainly—on the criminal side—during , as governed by the legal standards of and . Forensic scientists collect, preserve, and analyze scientific during the c ...
.
Butler A butler is a person who works in a house serving and is a domestic worker A domestic worker is a person who works within the scope of a residence. The term "domestic service" applies to the equivalent occupational category. In traditional Engl ...
(2009), p. 5.
More recently, Andrew Z. Fire and Craig C. Mello received the 2006 Nobel Prize for discovering the role of
RNA interference RNA interference (RNAi) is a biological process in which RNA Ribonucleic acid (RNA) is a polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substance or material consisting o ...
(
RNAi RNA interference (RNAi) is a biological process in which molecules are involved in sequence-specific suppression of gene expression by double-stranded RNA, through translational or transcriptional repression. Historically, RNAi was known by othe ...

RNAi
), in the silencing of
gene expression Gene expression is the process by which information from a gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance#History, Mendelian units of heredity..." (Greek language, ...

gene expression
. Chandan (2007), pp. 193–194.


Starting materials: the chemical elements of life

Around two dozen chemical elements are essential to various kinds of life, biological life. Most rare elements on Earth are not needed by life (exceptions being selenium and iodine), while a few common ones (aluminum and titanium) are not used. Most organisms share element needs, but there are a few differences between plants and animals. For example, ocean algae use bromine, but land plants and animals seem to need none. All animals require sodium, but some plants do not. Plants need boron and silicon, but animals may not (or may need ultra-small amounts). Just six elements—carbon, hydrogen, nitrogen, oxygen, calcium and phosphorus—make up almost 99% of the mass of living cells, including those in the human body (see composition of the human body for a complete list). In addition to the six major elements that compose most of the human body, humans require smaller amounts of possibly 18 more.


Biomolecules

The four main classes of molecules in biochemistry (often called biomolecules) are
carbohydrate is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are simple sugars soluble in water. Three common ex ...
s,
lipid In and , a lipid is a macro that is soluble in solvents. are typically s used to dissolve other naturally occurring hydrocarbon lipid s that do not (or do not easily) dissolve in water, including s, es, s, fat-soluble s (such as vitamins A, ...
s,
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
s, and
nucleic acid Nucleic acids are biopolymers, macromolecules, essential to all Organism, known forms of life. They are composed of nucleotides, which are the monomers made of three components: a pentose, 5-carbon sugar, a phosphate group and a nitrogenous base. ...

nucleic acid
s.#Slabaugh, Slabaugh (2007), pp. 3–6. Many biological molecules are polymers: in this terminology, monomers are relatively small macromolecules that are linked together to create large
macromolecule macromolecule A macromolecule is a very large molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neu ...
s known as polymers. When monomers are linked together to synthesize a Biopolymer, biological polymer, they undergo a process called Dehydration reaction, dehydration synthesis. Different macromolecules can assemble in larger complexes, often needed for biological activity.


Carbohydrates

Two of the main functions of carbohydrates are energy storage and providing structure. One of the common sugars known as glucose is carbohydrate, but not all carbohydrates are sugars. There are more carbohydrates on Earth than any other known type of biomolecule; they are used to store energy and genetic information, as well as play important roles in cell to Cell–cell interaction, cell interactions and Cell signaling, communications. The simplest type of carbohydrate is a monosaccharide, which among other properties contains carbon, hydrogen, and oxygen, mostly in a ratio of 1:2:1 (generalized formula C''n''H2''n''O''n'', where ''n'' is at least 3). Glucose (C6H12O6) is one of the most important carbohydrates; others include fructose (C6H12O6), the sugar commonly associated with the sweet taste of fruits,#Whiting, Whiting (1970), pp. 1–31. and deoxyribose (C5H10O4), a component of
DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral gro ...

DNA
. A monosaccharide can switch between Open-chain compound, acyclic (open-chain) form and a cyclic compound, cyclic form. The open-chain form can be turned into a ring of carbon atoms bridged by an oxygen atom created from the carbonyl group of one end and the hydroxyl group of another. The cyclic molecule has a hemiacetal or hemiketal group, depending on whether the linear form was an aldose or a ketose. In these cyclic forms, the ring usually has 5 or 6 atoms. These forms are called furanoses and pyranoses, respectively—by analogy with furan and pyran, the simplest compounds with the same carbon-oxygen ring (although they lack the carbon-carbon double bonds of these two molecules). For example, the aldohexose glucose may form a hemiacetal linkage between the hydroxyl on carbon 1 and the oxygen on carbon 4, yielding a molecule with a 5-membered ring, called glucofuranose. The same reaction can take place between carbons 1 and 5 to form a molecule with a 6-membered ring, called glucopyranose. Cyclic forms with a 7-atom ring called heptoses are rare. Two monosaccharides can be joined together by a Glycosidic bond, glycosidic or ether bond into a ''disaccharide'' through a dehydration reaction during which a molecule of water is released. The reverse reaction in which the glycosidic bond of a disaccharide is broken into two monosaccharides is termed ''hydrolysis''. The best-known disaccharide is sucrose or ordinary sugar, which consists of a glucose molecule and a fructose molecule joined together. Another important disaccharide is lactose found in milk, consisting of a glucose molecule and a galactose molecule. Lactose may be hydrolysed by lactase, and deficiency in this enzyme results in lactose intolerance. When a few (around three to six) monosaccharides are joined, it is called an ''oligosaccharide'' (''oligo-'' meaning "few"). These molecules tend to be used as markers and Cell signaling, signals, as well as having some other uses.#Varki, Varki (1999), p. 17. Many monosaccharides joined together form a polysaccharide. They can be joined together in one long linear chain, or they may be Branching (polymer chemistry), branched. Two of the most common polysaccharides are cellulose and glycogen, both consisting of repeating glucose monomers. ''Cellulose'' is an important structural component of plant's cell walls and ''glycogen'' is used as a form of energy storage in animals. Sugar can be characterized by having Reducing sugar, reducing or non-reducing ends. A reducing end of a carbohydrate is a carbon atom that can be in equilibrium with the open-chain aldehyde (aldose) or keto form (ketose). If the joining of monomers takes place at such a carbon atom, the free hydroxy group of the pyranose or furanose form is exchanged with an OH-side-chain of another sugar, yielding a full acetal. This prevents opening of the chain to the aldehyde or keto form and renders the modified residue non-reducing. Lactose contains a reducing end at its glucose moiety, whereas the galactose moiety forms a full acetal with the C4-OH group of glucose. Saccharose does not have a reducing end because of full acetal formation between the aldehyde carbon of glucose (C1) and the keto carbon of fructose (C2).


Lipids

Lipid, Lipids comprise a diverse range of molecules and to some extent is a catchall for relatively water-insoluble or nonpolar compounds of biological origin, including waxes, fatty acids, fatty-acid derived phospholipids, sphingolipids, glycolipids, and terpenoids (e.g., retinoids and steroids). Some lipids are linear, open-chain aliphatic molecules, while others have ring structures. Some are aromatic (with a cyclic [ring] and planar [flat] structure) while others are not. Some are flexible, while others are rigid. Lipids are usually made from one molecule of glycerol combined with other molecules. In triglycerides, the main group of bulk lipids, there is one molecule of glycerol and three fatty acids. Fatty acids are considered the monomer in that case, and may be Saturated and unsaturated compounds, saturated (no double bonds in the carbon chain) or unsaturated (one or more double bonds in the carbon chain). Most lipids have some Polar molecule, polar character in addition to being largely nonpolar. In general, the bulk of their structure is nonpolar or hydrophobic ("water-fearing"), meaning that it does not interact well with polar solvents like water. Another part of their structure is polar or hydrophilic ("water-loving") and will tend to associate with polar solvents like water. This makes them amphiphilic molecules (having both hydrophobic and hydrophilic portions). In the case of cholesterol, the polar group is a mere –OH (hydroxyl or alcohol). In the case of phospholipids, the polar groups are considerably larger and more polar, as described below. Lipids are an integral part of our daily diet. Most oils and milk products that we use for cooking and eating like butter, cheese, ghee etc., are composed of fats. Vegetable oils are rich in various polyunsaturated fatty acids (PUFA). Lipid-containing foods undergo digestion within the body and are broken into fatty acids and glycerol, which are the final degradation products of fats and lipids. Lipids, especially phospholipids, are also used in various pharmaceutical products, either as co-solubilisers (e.g., in parenteral infusions) or else as drug carrier components (e.g., in a liposome or transfersome).


Proteins

Proteins are very large molecules—macro-biopolymers—made from monomers called
amino acid Amino acids are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, a ...

amino acid
s. An amino acid consists of an alpha carbon atom attached to an amino group, –NH2, a carboxylic acid group, –COOH (although these exist as –NH3+ and –COO under physiologic conditions), a simple hydrogen atom, and a side chain commonly denoted as "–R". The side chain "R" is different for each amino acid of which there are 20 proteinogenic amino acid, standard ones. It is this "R" group that made each amino acid different, and the properties of the side-chains greatly influence the overall Protein tertiary structure, three-dimensional conformation of a protein. Some amino acids have functions by themselves or in a modified form; for instance, glutamate functions as an important neurotransmitter. Amino acids can be joined via a peptide bond. In this Dehydration reaction, dehydration synthesis, a water molecule is removed and the peptide bond connects the nitrogen of one amino acid's amino group to the carbon of the other's carboxylic acid group. The resulting molecule is called a ''dipeptide'', and short stretches of amino acids (usually, fewer than thirty) are called ''peptides'' or polypeptides. Longer stretches merit the title ''proteins''. As an example, the important blood blood plasma, serum protein human serum albumin, albumin contains 585 amino acid residues.#Metzler, Metzler (2001), p. 58. Proteins can have structural and/or functional roles. For instance, movements of the proteins actin and myosin ultimately are responsible for the contraction of skeletal muscle. One property many proteins have is that they specifically bind to a certain molecule or class of molecules—they may be ''extremely'' selective in what they bind. Antibody, Antibodies are an example of proteins that attach to one specific type of molecule. Antibodies are composed of heavy and light chains. Two heavy chains would be linked to two light chains through disulfide linkages between their amino acids. Antibodies are specific through variation based on differences in the N-terminal domain. The enzyme-linked immunosorbent assay (ELISA), which uses antibodies, is one of the most sensitive tests modern medicine uses to detect various biomolecules. Probably the most important proteins, however, are the
enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates in ...

enzyme
s. Virtually every reaction in a living cell requires an enzyme to lower the activation energy of the reaction. These molecules recognize specific reactant molecules called ''substrate (biochemistry), substrates''; they then Catalysis, catalyze the reaction between them. By lowering the activation energy, the enzyme speeds up that reaction by a rate of 1011 or more; a reaction that would normally take over 3,000 years to complete spontaneously might take less than a second with an enzyme. The enzyme itself is not used up in the process and is free to catalyze the same reaction with a new set of substrates. Using various modifiers, the activity of the enzyme can be regulated, enabling control of the biochemistry of the cell as a whole. The structure of proteins is traditionally described in a hierarchy of four levels. The primary structure of a protein consists of its linear sequence of amino acids; for instance, "alanine-glycine-tryptophan-serine-glutamate-asparagine-glycine-lysine-…". Secondary structure is concerned with local morphology (morphology being the study of structure). Some combinations of amino acids will tend to curl up in a coil called an alpha helix, α-helix or into a sheet called a Beta sheet, β-sheet; some α-helixes can be seen in the hemoglobin schematic above. Tertiary structure is the entire three-dimensional shape of the protein. This shape is determined by the sequence of amino acids. In fact, a single change can change the entire structure. The alpha chain of hemoglobin contains 146 amino acid residues; substitution of the glutamate residue at position 6 with a valine residue changes the behavior of hemoglobin so much that it results in sickle-cell disease. Finally, quaternary structure is concerned with the structure of a protein with multiple peptide subunits, like hemoglobin with its four subunits. Not all proteins have more than one subunit. Ingested proteins are usually broken up into single amino acids or dipeptides in the small intestine and then absorbed. They can then be joined to form new proteins. Intermediate products of glycolysis, the citric acid cycle, and the pentose phosphate pathway can be used to form all twenty amino acids, and most bacteria and plants possess all the necessary enzymes to synthesize them. Humans and other mammals, however, can synthesize only half of them. They cannot synthesize isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Because they must be ingested, these are the essential amino acids. Mammals do possess the enzymes to synthesize alanine, asparagine, aspartate, cysteine, glutamate, glutamine, glycine, proline, serine, and tyrosine, the nonessential amino acids. While they can synthesize arginine and histidine, they cannot produce it in sufficient amounts for young, growing animals, and so these are often considered essential amino acids. If the amino group is removed from an amino acid, it leaves behind a carbon skeleton called an α-keto acid. Enzymes called transaminases can easily transfer the amino group from one amino acid (making it an α-keto acid) to another α-keto acid (making it an amino acid). This is important in the biosynthesis of amino acids, as for many of the pathways, intermediates from other biochemical pathways are converted to the α-keto acid skeleton, and then an amino group is added, often via transamination. The amino acids may then be linked together to form a protein. A similar process is used to break down proteins. It is first hydrolyzed into its component amino acids. Free ammonia (NH3), existing as the ammonium ion (NH4+) in blood, is toxic to life forms. A suitable method for excreting it must therefore exist. Different tactics have evolved in different animals, depending on the animals' needs. Unicellular organisms simply release the ammonia into the environment. Likewise, Osteichthyes, bony fish can release the ammonia into the water where it is quickly diluted. In general, mammals convert the ammonia into urea, via the urea cycle. In order to determine whether two proteins are related, or in other words to decide whether they are homologous or not, scientists use sequence-comparison methods. Methods like sequence alignments and structural alignments are powerful tools that help scientists identify Sequence homology, homologies between related molecules. The relevance of finding homologies among proteins goes beyond forming an evolutionary pattern of Protein family, protein families. By finding how similar two protein sequences are, we acquire knowledge about their structure and therefore their function.


Nucleic acids

Nucleic acids, so-called because of their prevalence in cellular cell nucleus, nuclei, is the generic name of the family of biopolymers. They are complex, high-molecular-weight biochemical macromolecules that can convey genetic information in all living cells and viruses. The monomers are called nucleotides, and each consists of three components: a nitrogenous heterocyclic base (chemistry), base (either a purine or a pyrimidine), a pentose sugar, and a phosphate group. The most common nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The phosphate group and the sugar of each nucleotide bond with each other to form the backbone of the nucleic acid, while the sequence of nitrogenous bases stores the information. The most common nitrogenous bases are adenine, cytosine, guanine, thymine, and uracil. The nitrogenous bases of each strand of a nucleic acid will form hydrogen bonds with certain other nitrogenous bases in a complementary strand of nucleic acid (similar to a zipper). Adenine binds with thymine and uracil, thymine binds only with adenine, and cytosine and guanine can bind only with one another. Adenine and Thymine & Adenine and Uracil contains two hydrogen Bonds, while Hydrogen Bonds formed between cytosine and guanine are three in number. Aside from the genetic material of the cell, nucleic acids often play a role as second messengers, as well as forming the base molecule for adenosine triphosphate (ATP), the primary energy-carrier molecule found in all living organisms. Also, the nitrogenous bases possible in the two nucleic acids are different: adenine, cytosine, and guanine occur in both RNA and DNA, while thymine occurs only in DNA and uracil occurs in RNA.


Metabolism


Carbohydrates as energy source

Glucose is an energy source in most life forms. For instance, polysaccharides are broken down into their monomers by
enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates in ...

enzyme
s (glycogen phosphorylase removes glucose residues from glycogen, a polysaccharide). Disaccharides like lactose or sucrose are cleaved into their two component monosaccharides.


Glycolysis (anaerobic)

Glucose is mainly metabolized by a very important ten-step Metabolic pathway, pathway called
glycolysis Glycolysis is the metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of on ...

glycolysis
, the net result of which is to break down one molecule of glucose into two molecules of pyruvate. This also produces a net two molecules of Adenosine triphosphate, ATP, the energy currency of cells, along with two reducing equivalents of converting Nicotinamide adenine dinucleotide, NAD+ (nicotinamide adenine dinucleotide: oxidized form) to NADH (nicotinamide adenine dinucleotide: reduced form). This does not require oxygen; if no oxygen is available (or the cell cannot use oxygen), the NAD is restored by converting the pyruvate to lactic acid, lactate (lactic acid) (e.g., in humans) or to ethanol plus carbon dioxide (e.g., in yeast). Other monosaccharides like galactose and fructose can be converted into intermediates of the glycolytic pathway.


Aerobic

In aerobic glycolysis, aerobic cells with sufficient oxygen, as in most human cells, the pyruvate is further metabolized. It is irreversibly converted to acetyl-CoA, giving off one carbon atom as the waste product carbon dioxide, generating another reducing equivalent as NADH. The two molecules acetyl-CoA (from one molecule of glucose) then enter the citric acid cycle, producing two molecules of ATP, six more NADH molecules and two reduced (ubi)quinones (via FADH2, FADH2 as enzyme-bound cofactor), and releasing the remaining carbon atoms as carbon dioxide. The produced NADH and quinol molecules then feed into the enzyme complexes of the respiratory chain, an electron transport system transferring the electrons ultimately to oxygen and conserving the released energy in the form of a proton gradient over a membrane (inner mitochondrial membrane in eukaryotes). Thus, oxygen is reduced to water and the original electron acceptors NAD+ and quinone are regenerated. This is why humans breathe in oxygen and breathe out carbon dioxide. The energy released from transferring the electrons from high-energy states in NADH and quinol is conserved first as proton gradient and converted to ATP via ATP synthase. This generates an additional ''28'' molecules of ATP (24 from the 8 NADH + 4 from the 2 quinols), totaling to 32 molecules of ATP conserved per degraded glucose (two from glycolysis + two from the citrate cycle). It is clear that using oxygen to completely oxidize glucose provides an organism with far more energy than any oxygen-independent metabolic feature, and this is thought to be the reason why complex life appeared only after Earth's atmosphere accumulated large amounts of oxygen.


Gluconeogenesis

In vertebrates, vigorously contracting skeletal muscles (during weightlifting or sprinting, for example) do not receive enough oxygen to meet the energy demand, and so they shift to Fermentation (biochemistry), anaerobic metabolism, converting glucose to lactate. The combination of glucose from noncarbohydrates origin, such as fat and proteins. This only happens when glycogen supplies in the liver are worn out. The pathway is a crucial reversal of
glycolysis Glycolysis is the metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of on ...

glycolysis
from pyruvate to glucose and can utilize many sources like amino acids, glycerol and Krebs Cycle. Large scale protein and fat catabolism usually occur when those suffer from starvation or certain endocrine disorders. The liver regenerates the glucose, using a process called gluconeogenesis. This process is not quite the opposite of glycolysis, and actually requires three times the amount of energy gained from glycolysis (six molecules of ATP are used, compared to the two gained in glycolysis). Analogous to the above reactions, the glucose produced can then undergo glycolysis in tissues that need energy, be stored as glycogen (or starch in plants), or be converted to other monosaccharides or joined into di- or oligosaccharides. The combined pathways of glycolysis during exercise, lactate's crossing via the bloodstream to the liver, subsequent gluconeogenesis and release of glucose into the bloodstream is called the Cori cycle.


Relationship to other "molecular-scale" biological sciences

Researchers in biochemistry use specific techniques native to biochemistry, but increasingly combine these with techniques and ideas developed in the fields of genetics,
molecular biology Molecular biology is the branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, molecular synthesis, modification, mechanisms, and interaction ...
, and biophysics. There is not a defined line between these disciplines. Biochemistry studies the
chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during a with other . ...

chemistry
required for biological activity of molecules,
molecular biology Molecular biology is the branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, molecular synthesis, modification, mechanisms, and interaction ...
studies their biological activity, genetics studies their heredity, which happens to be carried by their genome. This is shown in the following schematic that depicts one possible view of the relationships between the fields: * ''Biochemistry'' is the study of the chemical substances and vital processes occurring in live
organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological me ...

organism
s. Biochemists focus heavily on the role, function, and structure of biomolecules. The study of the chemistry behind biological processes and the synthesis of biologically active molecules are applications of biochemistry. Biochemistry studies life at the atomic and molecular level. * ''Genetics'' is the study of the effect of genetic differences in organisms. This can often be inferred by the absence of a normal component (e.g. one
gene In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mecha ...

gene
). The study of "mutants" – organisms that lack one or more functional components with respect to the so-called "wild type" or normal phenotype. Genetic interactions (epistasis) can often confound simple interpretations of such "Gene knockout, knockout" studies. * ''Molecular biology'' is the study of molecular underpinnings of the biological phenomena, focusing on molecular synthesis, modification, mechanisms and interactions. The central dogma of molecular biology, where genetic material is transcribed into RNA and then translated into
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
, despite being oversimplified, still provides a good starting point for understanding the field. This concept has been revised in light of emerging novel roles for RNA. * 'Chemical biology' seeks to develop new tools based on small molecules that allow minimal perturbation of biological systems while providing detailed information about their function. Further, chemical biology employs biological systems to create non-natural hybrids between biomolecules and synthetic devices (for example emptied viral capsids that can deliver gene therapy or Pharmaceutical drug, drug molecules).


Extremophiles

Extremophiles are microorganisms that live in extreme conditions, some of which may provide some exceptions or variations on some of the natural laws cited above. For example, in July 2019, a scientific study of Kidd Mine in Canada discovered sulfur-breathing organisms that live 7900 feet below the surface and absorb sulfur instead of oxygen to facilitate cellular respiration. These organisms are also remarkable due to eating rocks such as pyrite as their regular food source.Strange life-forms found deep in a mine point to vast 'underground Galapagos'
By Corey S. Powell, Sept. 7, 2019, nbcnews.com.
The DNA polymerase of the thermophile bacteria ''Thermus aquaticus'', extracted in 1968 and named Taq polymerase, ''Taq'' polymerase, is a biochemical DNA replicator resistant to relative high temperatures (50-80 °C), which has allowed molecular biologists to ease complications in the Polymerase chain reaction, PCR (Polymerase Chain Reaction) method.


See also


Lists

* List of important publications in chemistry#Biochemistry, Important publications in biochemistry (chemistry) * List of biochemistry topics * List of biochemists * List of biomolecules


See also

* Astrobiology * Biochemistry (journal) * Biological Chemistry (journal) * Biophysics * Chemical ecology * Computational biomodeling * Dedicated bio-based chemical * Enzyme Commission number, EC number * Hypothetical types of biochemistry * International Union of Biochemistry and Molecular Biology * Metabolome * Metabolomics * Molecular biology * Molecular medicine * Plant biochemistry * Proteolysis * Small molecule * Structural biology * TCA cycle


Notes

a. Fructose is not the only sugar found in fruits. Glucose and sucrose are also found in varying quantities in various fruits, and sometimes exceed the fructose present. For example, 32% of the edible portion of a date (fruit), date is glucose, compared with 24% fructose and 8% sucrose. However, peaches contain more sucrose (6.66%) than they do fructose (0.93%) or glucose (1.47%).#Whiting, Whiting, G.C. (1970), p. 5.


References


Cited literature

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *


Further reading

* Fruton, Joseph S. ''Proteins, Enzymes, Genes: The Interplay of Chemistry and Biology''. Yale University Press: New Haven, 1999. * Keith Roberts, Martin Raff, Bruce Alberts, Peter Walter, Julian Lewis and Alexander Johnson, ''Molecular Biology of the Cell'' ** 4th Edition, Routledge, March, 2002, hardcover, 1616 pp. ** 3rd Edition, Garland, 1994, ** 2nd Edition, Garland, 1989, * Kohler, Robert. ''From Medical Chemistry to Biochemistry: The Making of a Biomedical Discipline''. Cambridge University Press, 1982. *


External links

*
The Virtual Library of Biochemistry, Molecular Biology and Cell Biology

Biochemistry, 5th ed.
Full text of Berg, Tymoczko, and Stryer, courtesy of National Center for Biotechnology Information, NCBI.
SystemsX.ch – The Swiss Initiative in Systems Biology

Full text of Biochemistry
by Kevin and Indira, an introductory biochemistry textbook. {{Authority control Biochemistry, Biotechnology Molecular biology