Biochemistry

For the journal, see Biochemistry (journal).Biological Chemistry redirects here. For the journalformerly named Biological Chemistry Hoppe-Seyler, seeBiological Chemistry (journal).

Biochemistry, sometimes called biological chemistry,is the study of chemical processes within and relatingto living organisms.[1] By controlling information owthrough biochemical signaling and the ow of chemicalenergy through metabolism, biochemical processes giverise to the complexity of life. Over the last 40 years,biochemistry has become so successful at explaining liv-ing processes that now almost all areas of the life sci-ences from botany to medicine are engaged in biochem-ical research.[2] Today, the main focus of pure biochem-istry is in understanding how biological molecules giverise to the processes that occur within living cells, whichin turn relates greatly to the study and understanding ofwhole organisms.Biochemistry is closely related to molecular biology, thestudy of the molecular mechanisms by which genetic in-formation encoded in DNA is able to result in the pro-cesses of life. Depending on the exact denition of theterms used, molecular biology can be thought of as abranch of biochemistry, or biochemistry as a tool withwhich to investigate and study molecular biology.Much of biochemistry deals with the structures, functionsand interactions of biological macromolecules, such asproteins, nucleic acids, carbohydrates and lipids, whichprovide the structure of cells and perform many of thefunctions associated with life. The chemistry of the cellalso depends on the reactions of smaller molecules andions. These can be inorganic, for example water andmetal ions, or organic, for example the amino acids whichare used to synthesize proteins. The mechanisms bywhich cells harness energy from their environment viachemical reactions are known as metabolism. The nd-ings of biochemistry are applied primarily in medicine,nutrition, and agriculture. In medicine, biochemists in-vestigate the causes and cures of disease. In nutrition,they study how to maintain health and study the eectsof nutritional deciencies. In agriculture, biochemists in-vestigate soil and fertilizers, and try to discover ways toimprove crop cultivation, crop storage and pest control.

1 HistoryMain article: History of biochemistryIt once was generally believed that life and its materi-

Gerty Cori and Carl Cori jointly won the Nobel Prize in 1947 fortheir discovery of the Cori cycle at RPMI.

als had some essential property or substance (often re-ferred to as the "vital principle") distinct from any foundin non-living matter, and it was thought that only livingbeings could produce the molecules of life.[3] Then, in1828, Friedrich Whler published a paper on the synthe-sis of urea, proving that organic compounds can be cre-ated articially.[4]

The beginning of biochemistrymay have been the discov-ery of the rst enzyme, diastase (today called amylase),in 1833 by Anselme Payen.[5] Eduard Buchner con-tributed the rst demonstration of a complex biochem-ical process outside a cell in 1896: alcoholic fermenta-tion in cell extracts of yeast.[6] Although the term bio-chemistry seems to have been rst used in 1882, itis generally accepted that the formal coinage of bio-chemistry occurred in 1903 by Carl Neuberg, a Germanchemist.[7] Since then, biochemistry has advanced, es-pecially since the mid-20th century, with the develop-ment of new techniques such as chromatography, X-ray

1

2 3 BIOMOLECULES

diraction, dual polarisation interferometry, NMR spec-troscopy, radioisotopic labeling, electron microscopy,and molecular dynamics simulations. These techniquesallowed for the discovery and detailed analysis of manymolecules and metabolic pathways of the cell, such asglycolysis and the Krebs cycle (citric acid cycle).Another signicant historic event in biochemistry is thediscovery of the gene and its role in the transfer of in-formation in the cell. This part of biochemistry is of-ten called molecular biology.[8] In the 1950s, James D.Watson, Francis Crick, Rosalind Franklin, and MauriceWilkins were instrumental in solving DNA structureand suggesting its relationship with genetic transfer ofinformation.[9] In 1958, George Beadle and EdwardTatum received the Nobel Prize for work in fungi show-ing that one gene produces one enzyme.[10] In 1988,Colin Pitchfork was the rst person convicted of mur-der with DNA evidence, which led to growth of forensicscience.[11] More recently, Andrew Z. Fire and Craig C.Mello received the 2006 Nobel Prize for discovering therole of RNA interference (RNAi), in the silencing of geneexpression.[12]

2 Starting materials: the chemicalelements of life

Main articles: Composition of the human body andDietary mineral

Around two dozen of the 92 naturally occurring chemicalelements are essential to various kinds of biological life.Most rare elements on Earth are not needed by life (ex-ceptions being selenium and iodine), while a few com-mon ones (aluminum and titanium) are not used. Mostorganisms share element needs, but there are a few dif-ferences between plants and animals. For example oceanalgae use bromine but land plants and animals seem toneed none. All animals require sodium, but some plantsdo not. Plants need boron and silicon, but animals maynot (or may need ultra-small amounts).Just six elementscarbon, hydrogen, nitrogen, oxygen,calcium, and phosphorusmake up almost 99% of themass of a human body (see composition of the humanbody for a complete list). In addition to the six majorelements that compose most of the human body, humansrequire smaller amounts of possibly 18 more.[13]

3 BiomoleculesThe four main classes of molecules in biochemistry(often called biomolecules) are carbohydrates, lipids,proteins, and nucleic acids. Many biological moleculesare polymers: in this terminology, monomers are rela-

tively small micromolecules that are linked together tocreate large macromolecules known as polymers. Whenmonomers are linked together to synthesize a biologicalpolymer, they undergo a process called dehydration syn-thesis. Dierent macromolecules can assemble in largercomplexes, often needed for biological activity.

3.1 Carbohydrates

Main articles: Carbohydrate, Monosaccharide,Disaccharide and PolysaccharideCarbohydrates are made from monomers called

A molecule of sucrose (glucose + fructose), a disaccharide.

monosaccharides. Some of these monosaccharidesinclude glucose (C6H12O6), fructose (C6H12O6), anddeoxyribose (C5H10O4). When two monosaccharidesundergo dehydration synthesis, water is produced, as twohydrogen atoms and one oxygen atom are lost from thetwo monosaccharides hydroxyl group.

3.2 Lipids

Main articles: Lipid, Glycerol and Fatty acidLipids are usually made from one molecule of glycerol

A triglyceride with a glycerol molecule on the left and three fattyacids coming o it.

combinedwith othermolecules. In triglycerides, themaingroup of bulk lipids, there is one molecule of glycerol andthree fatty acids. Fatty acids are considered the monomerin that case, and may be saturated (no double bonds in thecarbon chain) or unsaturated (one or more double bondsin the carbon chain).Lipids, especially phospholipids, are also used in variouspharmaceutical products, either as co-solubilisers (e.g., in

3parenteral infusions) or else as drug carrier components(e.g., in a liposome or transfersome).

3.3 Proteins

Main articles: Proteins and Amino AcidsProteins are very large molecules macro-biopolymers

The general structure of an -amino acid, with the amino groupon the left and the carboxyl group on the right.

made frommonomers called amino acids. There are 20standard amino acids, each containing a carboxyl group,an amino group, and a side-chain (known as an Rgroup). The R group is what makes each amino aciddierent, and the properties of the side-chains greatly in-uence the overall three-dimensional conformation of aprotein. When amino acids combine, they form a specialbond called a peptide bond through dehydration synthe-sis, and become a polypeptide, or protein.In order to determine whether two proteins are related, orin other words to decide whether they are homologous ornot, scientists use sequence-comparison methods. Meth-ods like Sequence Alignments and Structural Alignmentsare powerful tools that help scientists identify homologiesbetween related molecules.[14]

The relevance of nding homologies among proteins goesbeyond forming an evolutionary pattern of protein fam-ilies. By nding how similar two protein sequences are,we acquire knowledge about their structure and thereforetheir function.

3.4 Nucleic acids

Main articles: Nucleic acid, DNA, RNA and Nucleotides

Nucleic acids are the molecules that make up DNA, anextremely important substance that all cellular organ-isms use to store their genetic information. The mostcommon nucleic acids are deoxyribonucleic acid (DNA)and ribonucleic acid (RNA). Their monomers are callednucleotides. A nucleotide consists of a phosphate group,

Phosphate-deoxyribosebackbone

Adenine

CytosineGuanine

Thymine

O

O

O

O O

O

O

O O

O O

O

O

O

O

O

O O

O

O

O

O O

O O

O

O O

O

O O

O O

O

O

O O

O

N

N N

N

N

N

N

N

N N

N N N

N

N

N N N

N N

O

O

O

O

O

O

O

O

O

O

P

P P

P

P

P

P

P

NH 2

OH

OH

NH

H 2 N

HN

NH 2

H 2 N

HN

H 2 N

NH

NH 2

3 end

5 end3 end

5 end

The structure of deoxyribonucleic acid (DNA), the picture showsthe monomers being put together.

a ribose sugar, and a nitrogenous base. The phosphategroup and the sugar of each nucleotide bond with eachother to form the backbone of the nucleic acid, whilethe sequence of nitrogenous bases stores the informa-tion. The most common nitrogenous bases are adenine,cytosine, guanine, thymine, and uracil. The nitrogenousbases of each strand of a nucleic acid will form hydrogenbonds with certain other nitrogenous bases in a comple-mentary strand of nucleic acid (similar to a zipper). Ade-nine binds with thymine and uracil; Thymine binds onlywith adenine; and cytosine and guanine can bind only withone another.

4 CarbohydratesMain article: Carbohydrate

The function of carbohydrates includes energy storageand providing structure. Sugars are carbohydrates, butnot all carbohydrates are sugars. There are more car-bohydrates on Earth than any other known type ofbiomolecule; they are used to store energy and geneticinformation, as well as play important roles in cell to cellinteractions and communications.

4.1 MonosaccharidesThe simplest type of carbohydrate is a monosaccharide,which between other properties contains carbon, hydro-gen, and oxygen, mostly in a ratio of 1:2:1 (generalizedformula CnHnOn, where n is at least 3). Glucose, one

4 4 CARBOHYDRATES

Glucose

of the most important carbohydrates, is an example ofa monosaccharide. So is fructose, the sugar commonlyassociated with the sweet taste of fruits.[15][a] Some car-bohydrates (especially after condensation to oligo- andpolysaccharides) contain less carbon relative to H and O,which still are present in 2:1 (H:O) ratio. Monosaccha-rides can be grouped into aldoses (having an aldehydegroup at the end of the chain, e.g. glucose) and ketoses(having a keto group in their chain; e.g. fructose). Bothaldoses and ketoses occur in an equilibrium (starting withchain lengths of C4) cyclic forms. These are generated bybond formation between one of the hydroxyl groups ofthe sugar chain with the carbon of the aldehyde or ketogroup to form a hemiacetal bond. This leads to saturatedve-membered (in furanoses) or six-membered (in pyra-noses) heterocyclic rings containing one O as heteroatom.

4.2 Disaccharides

O

OOH H

H

H

HH

H

H

HOHO

OH

OH

OH

CH OH2CH OH2

CH OH2

Sucrose: ordinary table sugar and probably the most familiarcarbohydrate.

Two monosaccharides can be joined using dehydrationsynthesis, in which a hydrogen atom is removed fromthe end of one molecule and a hydroxyl group (OH)is removed from the other; the remaining residues arethen attached at the sites from which the atoms wereremoved. The HOH or H2O is then released as amolecule of water, hence the term dehydration. The newmolecule, consisting of two monosaccharides, is called adisaccharide and is conjoined together by a glycosidic orether bond. The reverse reaction can also occur, using amolecule of water to split up a disaccharide and break theglycosidic bond; this is termed hydrolysis. The most well-known disaccharide is sucrose, ordinary sugar (in scien-

tic contexts, called table sugar or cane sugar to dieren-tiate it from other sugars). Sucrose consists of a glucosemolecule and a fructose molecule joined together. An-other important disaccharide is lactose, consisting of aglucose molecule and a galactose molecule. As most hu-mans age, the production of lactase, the enzyme that hy-drolyzes lactose back into glucose and galactose, typicallydecreases. This results in lactase deciency, also calledlactose intolerance.Sugar polymers are characterized by having reducing ornon-reducing ends. A reducing end of a carbohydrate isa carbon atom that can be in equilibrium with the open-chain aldehyde or keto form. If the joining of monomerstakes place at such a carbon atom, the free hydroxy groupof the pyranose or furanose form is exchanged with anOH-side-chain of another sugar, yielding a full acetal.This prevents opening of the chain to the aldehyde orketo form and renders the modied residue non-reducing.Lactose contains a reducing end at its glucose moiety,whereas the galactose moiety form a full acetal with theC4-OH group of glucose. Saccharose does not have a re-ducing end because of full acetal formation between thealdehyde carbon of glucose (C1) and the keto carbon offructose (C2).

4.3 Oligosaccharides and polysaccharides

Cellulose as polymer of -D-glucose

When a few (around three to six) monosaccharides arejoined, it is called an oligosaccharide (oligo- meaningfew). These molecules tend to be used as markersand signals, as well as having some other uses. Manymonosaccharides joined together make a polysaccharide.They can be joined together in one long linear chain,or they may be branched. Two of the most commonpolysaccharides are cellulose and glycogen, both consist-ing of repeating glucose monomers.

Cellulose is made by plants and is an important struc-tural component of their cell walls. Humans can nei-ther manufacture nor digest it.

Glycogen, on the other hand, is an animal carbohy-drate; humans and other animals use it as a form ofenergy storage.

54.4 Use of carbohydrates as an energysource

Main article: Carbohydrate metabolism

Glucose is the major energy source in most life forms.For instance, polysaccharides are broken down intotheir monomers (glycogen phosphorylase removes glu-cose residues from glycogen). Disaccharides like lactoseor sucrose are cleaved into their two componentmonosac-charides.

4.4.1 Glycolysis (anaerobic)

Glucose is mainly metabolized by a very important ten-step pathway called glycolysis, the net result of which is tobreak down one molecule of glucose into two moleculesof pyruvate; this also produces a net two molecules ofATP, the energy currency of cells, along with two re-ducing equivalents as converting NAD+ to NADH. Thisdoes not require oxygen; if no oxygen is available (or thecell cannot use oxygen), the NAD is restored by convert-ing the pyruvate to lactate (lactic acid) (e.g., in humans)or to ethanol plus carbon dioxide (e.g., in yeast). Othermonosaccharides like galactose and fructose can be con-verted into intermediates of the glycolytic pathway.[16]

4.4.2 Aerobic

In aerobic cells with sucient oxygen, as in most humancells, the pyruvate is further metabolized. It is irreversiblyconverted to acetyl-CoA, giving o one carbon atom asthe waste product carbon dioxide, generating another re-ducing equivalent as NADH. The two molecules acetyl-CoA (from one molecule of glucose) then enter the citricacid cycle, producing two more molecules of ATP, sixmore NADH molecules and two reduced (ubi)quinones(via FADH2 as enzyme-bound cofactor), and releasingthe remaining carbon atoms as carbon dioxide. The pro-duced NADH and quinol molecules then feed into theenzyme complexes of the respiratory chain, an electrontransport system transferring the electrons ultimately tooxygen and conserving the released energy in the formof a proton gradient over a membrane (inner mitochon-drial membrane in eukaryotes). Thus, oxygen is reducedto water and the original electron acceptors NAD+ andquinone are regenerated. This is why humans breathe inoxygen and breathe out carbon dioxide. The energy re-leased from transferring the electrons from high-energystates in NADH and quinol is conserved rst as protongradient and converted to ATP via ATP synthase. Thisgenerates an additional 28molecules of ATP (24 from the8 NADH+ 4 from the 2 quinols), totaling to 32moleculesof ATP conserved per degraded glucose (two from gly-colysis + two from the citrate cycle). It is clear that usingoxygen to completely oxidize glucose provides an organ-

ism with far more energy than any oxygen-independentmetabolic feature, and this is thought to be the reason whycomplex life appeared only after Earths atmosphere ac-cumulated large amounts of oxygen.

4.4.3 Gluconeogenesis

Main article: Gluconeogenesis

In vertebrates, vigorously contracting skeletal muscles(during weightlifting or sprinting, for example) do not re-ceive enough oxygen to meet the energy demand, and sothey shift to anaerobic metabolism, converting glucose tolactate. The liver regenerates the glucose, using a processcalled gluconeogenesis. This process is not quite the op-posite of glycolysis, and actually requires three times theamount of energy gained from glycolysis (six moleculesof ATP are used, compared to the two gained in gly-colysis). Analogous to the above reactions, the glucoseproduced can then undergo glycolysis in tissues that needenergy, be stored as glycogen (or starch in plants), or beconverted to other monosaccharides or joined into di- oroligosaccharides. The combined pathways of glycolysisduring exercise, lactates crossing via the bloodstream tothe liver, subsequent gluconeogenesis and release of glu-cose into the bloodstream is called the Cori cycle.[17]

5 ProteinsMain article: ProteinLike carbohydrates, some proteins perform largely struc-

A schematic of hemoglobin. The red and blue ribbons representthe protein globin; the green structures are the heme groups.

tural roles. For instance, movements of the proteins actinand myosin ultimately are responsible for the contraction

6 5 PROTEINS

of skeletal muscle. One property many proteins have isthat they specically bind to a certain molecule or class ofmoleculesthey may be extremely selective in what theybind. Antibodies are an example of proteins that attach toone specic type of molecule. In fact, the enzyme-linkedimmunosorbent assay (ELISA), which uses antibodies, isone of the most sensitive tests modern medicine uses todetect various biomolecules. Probably the most impor-tant proteins, however, are the enzymes. These moleculesrecognize specic reactant molecules called substrates;they then catalyze the reaction between them. By low-ering the activation energy, the enzyme speeds up thatreaction by a rate of 1011 or more: a reaction that wouldnormally take over 3,000 years to complete spontaneouslymight take less than a second with an enzyme. The en-zyme itself is not used up in the process, and is free tocatalyze the same reaction with a new set of substrates.Using various modiers, the activity of the enzyme canbe regulated, enabling control of the biochemistry of thecell as a whole.In essence, proteins are chains of amino acids. An aminoacid consists of a carbon atom bound to four groups. Oneis an amino group, NH2, and one is a carboxylic acidgroup, COOH (although these exist as NH3+ andCOO under physiologic conditions). The third is asimple hydrogen atom. The fourth is commonly denoted"R and is dierent for each amino acid. There are20 standard amino acids. Some of these have functionsby themselves or in a modied form; for instance, gluta-mate functions as an important neurotransmitter. Also ifa glycine amino acid undergoes methylation to a pseudoalanine amino acid, it is an indication of cancer metasta-sis.

Generic amino acids (1) in neutral form, (2) as they exist physi-ologically, and (3) joined together as a dipeptide.

Amino acids can be joined via a peptide bond. In this de-hydration synthesis, a water molecule is removed and thepeptide bond connects the nitrogen of one amino acidsamino group to the carbon of the others carboxylic acidgroup. The resulting molecule is called a dipeptide, andshort stretches of amino acids (usually, fewer than thirty)are called peptides or polypeptides. Longer stretchesmerit the title proteins. As an example, the importantblood serum protein albumin contains 585 amino acidresidues.[18]

The structure of proteins is traditionally described in a hi-erarchy of four levels. The primary structure of a proteinsimply consists of its linear sequence of amino acids; forinstance, alanine-glycine-tryptophan-serine-glutamate-asparagine-glycine-lysine-". Secondary structure is

concerned with local morphology (morphology being thestudy of structure). Some combinations of amino acidswill tend to curl up in a coil called an -helix or into asheet called a -sheet; some -helixes can be seen in thehemoglobin schematic above. Tertiary structure is the en-tire three-dimensional shape of the protein. This shape isdetermined by the sequence of amino acids. In fact, asingle change can change the entire structure. The alphachain of hemoglobin contains 146 amino acid residues;substitution of the glutamate residue at position 6 witha valine residue changes the behavior of hemoglobinso much that it results in sickle-cell disease. Finally,quaternary structure is concerned with the structure ofa protein with multiple peptide subunits, like hemoglobinwith its four subunits. Not all proteins have more thanone subunit.[19]

Ingested proteins are usually broken up into single aminoacids or dipeptides in the small intestine, and then ab-sorbed. They can then be joined to make new proteins.Intermediate products of glycolysis, the citric acid cycle,and the pentose phosphate pathway can be used to makeall twenty amino acids, and most bacteria and plants pos-sess all the necessary enzymes to synthesize them. Hu-mans and other mammals, however, can synthesize onlyhalf of them. They cannot synthesize isoleucine, leucine,lysine, methionine, phenylalanine, threonine, tryptophan,and valine. These are the essential amino acids, sinceit is essential to ingest them. Mammals do possessthe enzymes to synthesize alanine, asparagine, aspartate,cysteine, glutamate, glutamine, glycine, proline, serine,and tyrosine, the nonessential amino acids. While theycan synthesize arginine and histidine, they cannot pro-duce it in sucient amounts for young, growing animals,and so these are often considered essential amino acids.If the amino group is removed from an amino acid, itleaves behind a carbon skeleton called an -keto acid. En-zymes called transaminases can easily transfer the aminogroup from one amino acid (making it an -keto acid) toanother -keto acid (making it an amino acid). This isimportant in the biosynthesis of amino acids, as for manyof the pathways, intermediates from other biochemicalpathways are converted to the -keto acid skeleton, andthen an amino group is added, often via transamination.The amino acids may then be linked together to make aprotein.[20]

A similar process is used to break down proteins. It isrst hydrolyzed into its component amino acids. Freeammonia (NH3), existing as the ammonium ion (NH4+)in blood, is toxic to life forms. A suitable method forexcreting it must therefore exist. Dierent tactics haveevolved in dierent animals, depending on the animalsneeds. Unicellular organisms, of course, simply releasethe ammonia into the environment. Likewise, bony shcan release the ammonia into the water where it is quicklydiluted. In general, mammals convert the ammonia intourea, via the urea cycle.[21]

76 LipidsMain article: Lipid

The term lipid composes a diverse range ofmolecules andto some extent is a catchall for relatively water-insolubleor nonpolar compounds of biological origin, includ-ing waxes, fatty acids, fatty-acid derived phospholipids,sphingolipids, glycolipids, and terpenoids (e.g., retinoidsand steroids). Some lipids are linear aliphatic molecules,while others have ring structures. Some are aromatic,while others are not. Some are exible, while others arerigid.[22]

Most lipids have some polar character in addition to beinglargely nonpolar. In general, the bulk of their structureis nonpolar or hydrophobic (water-fearing), meaningthat it does not interact well with polar solvents like wa-ter. Another part of their structure is polar or hydrophilic(water-loving) and will tend to associate with polar sol-vents like water. This makes them amphiphilic molecules(having both hydrophobic and hydrophilic portions). Inthe case of cholesterol, the polar group is a mere -OH(hydroxyl or alcohol). In the case of phospholipids, thepolar groups are considerably larger and more polar, asdescribed below.Lipids are an integral part of our daily diet. Most oilsand milk products that we use for cooking and eatinglike butter, cheese, ghee etc., are composed of fats.Vegetable oils are rich in various polyunsaturated fattyacids (PUFA). Lipid-containing foods undergo digestionwithin the body and are broken into fatty acids and glyc-erol, which are the nal degradation products of fats andlipids.

7 Nucleic acidsMain article: Nucleic acid

A nucleic acid is a complex, high-molecular-weight bio-chemical macromolecule composed of nucleotide chainsthat convey genetic information.[23] The most commonnucleic acids are deoxyribonucleic acid (DNA) and ri-bonucleic acid (RNA). Nucleic acids are found in all liv-ing cells and viruses. Aside from the genetic material ofthe cell, nucleic acids often play a role as second messen-gers, as well as forming the base molecule for adenosinetriphosphate (ATP), the primary energy-carrier moleculefound in all living organisms.Nucleic acid, so called because of its prevalence in cellu-lar nuclei, is the generic name of the family of biopoly-mers. The monomers are called nucleotides, and eachconsists of three components: a nitrogenous heterocyclicbase (either a purine or a pyrimidine), a pentose sugar,and a phosphate group. Dierent nucleic acid types dif-

fer in the specic sugar found in their chain (e.g., DNAor deoxyribonucleic acid contains 2-deoxyriboses). Also,the nitrogenous bases possible in the two nucleic acids aredierent: adenine, cytosine, and guanine occur in bothRNA and DNA, while thymine occurs only in DNA anduracil occurs in RNA.[24]

8 Relationship to othermolecular-scale biologicalsciences

Schematic relationship between biochemistry, genetics, andmolecular biology

Researchers in biochemistry use specic techniques na-tive to biochemistry, but increasingly combine these withtechniques and ideas developed in the elds of genetics,molecular biology and biophysics. There has never beena hard-line among these disciplines in terms of contentand technique. Today, the terms molecular biology andbiochemistry are nearly interchangeable. The followinggure is a schematic that depicts one possible view of therelationship between the elds:

Biochemistry is the study of the chemical substancesand vital processes occurring in living organisms.Biochemists focus heavily on the role, function, andstructure of biomolecules. The study of the chem-istry behind biological processes and the synthesisof biologically active molecules are examples of bio-chemistry.

Genetics is the study of the eect of genetic dif-ferences on organisms. Often this can be inferredby the absence of a normal component (e.g., onegene). The study of "mutants" organisms with achanged gene that leads to the organism being dif-ferent with respect to the so-called "wild type" or

8 11 REFERENCES

normal phenotype. Genetic interactions (epistasis)can often confound simple interpretations of suchknock-out or knock-in studies.

Molecular biology is the study of molecular under-pinnings of the process of replication, transcrip-tion and translation of the genetic material. Thecentral dogma of molecular biology where geneticmaterial is transcribed into RNA and then translatedinto protein, despite being an oversimplied pictureof molecular biology, still provides a good start-ing point for understanding the eld. This picture,however, is undergoing revision in light of emergingnovel roles for RNA.[25]

Chemical biology seeks to develop new tools basedon small molecules that allow minimal perturbationof biological systems while providing detailed in-formation about their function. Further, chemicalbiology employs biological systems to create non-natural hybrids between biomolecules and syntheticdevices (for example emptied viral capsids that candeliver gene therapy or drug molecules).

9 See alsoMain article: Outline of biochemistry

9.1 Lists Important publications in biochemistry (chemistry) List of biochemistry topics List of biochemists List of biomolecules

9.2 See also Chemical ecology Computational biomodeling EC number Hypothetical types of biochemistry International Union of Biochemistry and MolecularBiology

Metabolome Metabolomics Molecular medicine Plant biochemistry

Proteolysis Small molecule Structural biology

10 Notesa. ^ Fructose is not the only sugar found in fruits. Glu-cose and sucrose are also found in varying quantities invarious fruits, and indeed sometimes exceed the fructosepresent. For example, 32% of the edible portion of date isglucose, compared with 23.70% fructose and 8.20% su-crose. However, peaches contain more sucrose (6.66%)than they do fructose (0.93%) or glucose (1.47%).[26]

11 References[1] Biochemistry. acs.org.

[2] scientic term 'biochemistry'".

[3] Fiske, John (1890). Outlines of Cosmic Philosophy Basedon the Doctrines of Evolution, with Criticisms on the Pos-itive Philosophy, Volume 1. Boston and New York:Houghton, Miin. pp. 41920. Retrieved 16 February2015.

[4] Kauman, G.B.; Chooljian, S.H. (2001). FriedrichWhler (18001882), on the bicentennial of hisbirth. The Chemical Educator 6 (2): 121133.doi:10.1007/s00897010444a.

[5] Hunter (2000), p. 75.

[6] Hunter (2000), pp. 9698.

[7] Ben-Menahem, Ari (2009). Historical Encyclopedia ofNatural and Mathematical Sciences. Springer. p. 2982.ISBN 978-3-540-68831-0.

[8] Tropp (2012), p. 2.

[9] Tropp (2012), pp. 1920.

[10] Krebs, Jocelyn E.; Goldstein, Elliott S.; Lewin, Benjamin;Kilpatrick, Stephen T. (2012). Essential Genes. Jones &Bartlett Publishers. p. 32. ISBN 978-1-4496-1265-8.

[11] Butler, John M. (2009). Fundamentals of Forensic DNATyping. Academic Press. p. 5. ISBN 978-0-08-096176-7.

[12] Sen, Chandan K.; Roy, Sashwati (2007). miRNA:Licensed to kill the messenger. DNA Cell Biology26 (4): 193194. doi:10.1089/dna.2006.0567. PMID17465885.

[13] Ultratrace minerals. Authors: Nielsen, Forrest H. USDA,ARS Source: Modern nutrition in health and disease / ed-itors, Maurice E. Shils ... et al.. Baltimore : Williams &Wilkins, c1999., p. 283-303. Issue Date: 1999 URI:

9[14] Fariselli, Piero; Rossi, Ivan; Capriotti, Emidio; Casadio,Rita (2007). TheWWWH of remote homolog detection:the state of the art. Briengs in Bioinformatics 8 (2): 7887. doi:10.1093/bib/bbl032. PMID 17003074.

[15] Whiting, G.C (1970). Sugars. In A.C. Hulme. The Bio-chemistry of Fruits and their Products. Volume 1. London& New York: Academic Press. pp. 131.

[16] Fromm and Hargrove (2012), pp. 163180.

[17] Fromm and Hargrove (2012), pp. 183194.

[18] Metzler, David Everett; Metzler, Carol M. (2001).Biochemistry: The Chemical Reactions of Living Cells 1.Academic Press. p. 58. ISBN 978-0-12-492540-3.

[19] Fromm and Hargrove (2012), pp. 3551.

[20] Fromm and Hargrove (2012), pp. 279292.

[21] Sherwood, Lauralee; Klandorf, Hillar; Yancey, Paul H.(2012). Animal Physiology: From Genes to Organisms.Cengage Learning. p. 558. ISBN 978-0-8400-6865-1.

[22] Fromm and Hargrove (2012), pp. 2227.

[23] Voet, D. and Voet, J, G. (2011). Biochemistry (4th ed.).John Wiley & Sons Inc.: Hoboken, NJ

[24] Tropp (2012), pp. 59.

[25] Ulveling, Damien; Francastel, Claire; Hub, Flo-rent (2011). When one is better than two: RNAwith dual functions. Biochimie 93 (4): 633644.doi:10.1016/j.biochi.2010.11.004. PMID 21111023.

[26] Whiting, G.C. (1970), p.5

11.1 Cited literature Fromm, Herbert J.; Hargrove, Mark (2012). Essen-

tials of Biochemistry. Springer. ISBN 978-3-642-19623-2.

Hunter, Graeme K. (2000). Vital Forces: The Dis-covery of the Molecular Basis of Life. AcademicPress. ISBN 978-0-12-361811-5.

Tropp, Burton E. (2012). Molecular Biology (4thed.). Jones & Bartlett Learning. ISBN 978-1-4496-0091-4.

12 External links The Virtual Library of Biochemistry and Cell Biol-ogy

Biochemistry, 5th ed. Full text of Berg, Tymoczko,and Stryer, courtesy of NCBI.

Biochemistry, 2nd ed. Full text of Garrett and Gr-isham.

Biochemistry Animation (Narrated Flash anima-tions.)

SystemsX.ch - The Swiss Initiative in Systems Biol-ogy

Biochemistry Online Resources Lists of Biochem-istry departments, websites, journals, books and re-views, employment opportunities and events.

Full text of Biochemistry by Kevin and Indira, anintroductory biochemistry textbook.

10 13 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

13 Text and image sources, contributors, and licenses13.1 Text

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HistoryStarting materials: the chemical elements of life BiomoleculesCarbohydratesLipidsProteinsNucleic acids

CarbohydratesMonosaccharidesDisaccharidesOligosaccharides and polysaccharidesUse of carbohydrates as an energy sourceGlycolysis (anaerobic)AerobicGluconeogenesis

ProteinsLipidsNucleic acidsRelationship to other molecular-scale biological sciencesSee alsoLists See also

NotesReferencesCited literature

External links Text and image sources, contributors, and licensesTextImagesContent license