Simplified view of the cellular metabolism
The succinate dehydrogenase complex showing several cofactors, including flavin, iron–sulfur centers, and heme.
Structure of adenosine triphosphate (ATP), a central intermediate in energy metabolism
A simple [Fe2S2] cluster containing two iron atoms and two sulfur atoms, coordinated by four protein cysteine residues.
Structure of a triacylglycerol lipid
The redox reactions of nicotinamide adenine dinucleotide.
This is a diagram depicting a large set of human metabolic pathways.
Glucose can exist in both a straight-chain and ring form.
Structure of the coenzyme acetyl-CoA.The transferable acetyl group is bonded to the sulfur atom at the extreme left.
The structure of iron-containing hemoglobin. The protein subunits are in red and blue, and the iron-containing heme groups in green. From.
A simplified outline of the catabolism of proteins, carbohydrates and fats
Mechanism of ATP synthase. ATP is shown in red, ADP and phosphate in pink and the rotating stalk subunit in black.
Plant cells (bounded by purple walls) filled with chloroplasts (green), which are the site of photosynthesis
Simplified version of the steroid synthesis pathway with the intermediates isopentenyl pyrophosphate (IPP), dimethylallyl pyrophosphate (DMAPP), geranyl pyrophosphate (GPP) and squalene shown. Some intermediates are omitted for clarity.
Effect of insulin on glucose uptake and metabolism. Insulin binds to its receptor (1), which in turn starts many protein activation cascades (2). These include: translocation of Glut-4 transporter to the plasma membrane and influx of glucose (3), glycogen synthesis (4), glycolysis (5) and fatty acid synthesis (6).
Evolutionary tree showing the common ancestry of organisms from all three domains of life. Bacteria are colored blue, eukaryotes red, and archaea green. Relative positions of some of the phyla included are shown around the tree.
Metabolic network of the Arabidopsis thaliana citric acid cycle. Enzymes and metabolites are shown as red squares and the interactions between them as black lines.
Aristotle's metabolism as an open flow model
Santorio Santorio in his steelyard balance, from Ars de statica medicina, first published 1614

These group-transfer intermediates are called coenzymes.

- Metabolism

Therefore, these cofactors are continuously recycled as part of metabolism.

- Cofactor (biochemistry)
Simplified view of the cellular metabolism

10 related topics with Alpha

Overall

A representation of the 3D structure of the protein myoglobin showing turquoise α-helices. This protein was the first to have its structure solved by X-ray crystallography. Toward the right-center among the coils, a prosthetic group called a heme group (shown in gray) with a bound oxygen molecule (red).

Protein

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Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues.

Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues.

A representation of the 3D structure of the protein myoglobin showing turquoise α-helices. This protein was the first to have its structure solved by X-ray crystallography. Toward the right-center among the coils, a prosthetic group called a heme group (shown in gray) with a bound oxygen molecule (red).
John Kendrew with model of myoglobin in progress
Chemical structure of the peptide bond (bottom) and the three-dimensional structure of a peptide bond between an alanine and an adjacent amino acid (top/inset). The bond itself is made of the CHON elements.
Resonance structures of the peptide bond that links individual amino acids to form a protein polymer
A ribosome produces a protein using mRNA as template
The DNA sequence of a gene encodes the amino acid sequence of a protein
The crystal structure of the chaperonin, a huge protein complex. A single protein subunit is highlighted. Chaperonins assist protein folding.
Three possible representations of the three-dimensional structure of the protein triose phosphate isomerase. Left: All-atom representation colored by atom type. Middle: Simplified representation illustrating the backbone conformation, colored by secondary structure. Right: Solvent-accessible surface representation colored by residue type (acidic residues red, basic residues blue, polar residues green, nonpolar residues white).
Molecular surface of several proteins showing their comparative sizes. From left to right are: immunoglobulin G (IgG, an antibody), hemoglobin, insulin (a hormone), adenylate kinase (an enzyme), and glutamine synthetase (an enzyme).
The enzyme hexokinase is shown as a conventional ball-and-stick molecular model. To scale in the top right-hand corner are two of its substrates, ATP and glucose.
Ribbon diagram of a mouse antibody against cholera that binds a carbohydrate antigen
Proteins in different cellular compartments and structures tagged with green fluorescent protein (here, white)
Constituent amino-acids can be analyzed to predict secondary, tertiary and quaternary protein structure, in this case hemoglobin containing heme units

Some proteins have non-peptide groups attached, which can be called prosthetic groups or cofactors.

Many proteins are enzymes that catalyse biochemical reactions and are vital to metabolism.

The enzyme glucosidase converts the sugar maltose into two glucose sugars. Active site residues in red, maltose substrate in black, and NAD cofactor in yellow.

Enzyme

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Enzymes are proteins that act as biological catalysts (biocatalysts).

Enzymes are proteins that act as biological catalysts (biocatalysts).

The enzyme glucosidase converts the sugar maltose into two glucose sugars. Active site residues in red, maltose substrate in black, and NAD cofactor in yellow.
Eduard Buchner
Enzyme activity initially increases with temperature (Q10 coefficient) until the enzyme's structure unfolds (denaturation), leading to an optimal rate of reaction at an intermediate temperature.
Organisation of enzyme structure and lysozyme example. Binding sites in blue, catalytic site in red and peptidoglycan substrate in black.
Enzyme changes shape by induced fit upon substrate binding to form enzyme-substrate complex. Hexokinase has a large induced fit motion that closes over the substrates adenosine triphosphate and xylose. Binding sites in blue, substrates in black and Mg2+ cofactor in yellow.
Chemical structure for thiamine pyrophosphate and protein structure of transketolase. Thiamine pyrophosphate cofactor in yellow and xylulose 5-phosphate substrate in black.
The energies of the stages of a chemical reaction. Uncatalysed (dashed line), substrates need a lot of activation energy to reach a transition state, which then decays into lower-energy products. When enzyme catalysed (solid line), the enzyme binds the substrates (ES), then stabilizes the transition state (ES‡) to reduce the activation energy required to produce products (EP) which are finally released.
The metabolic pathway of glycolysis releases energy by converting glucose to pyruvate via a series of intermediate metabolites. Each chemical modification (red box) is performed by a different enzyme.
In phenylalanine hydroxylase over 300 different mutations throughout the structure cause phenylketonuria. Phenylalanine substrate and tetrahydrobiopterin coenzyme in black, and Fe2+ cofactor in yellow.
Hereditary defects in enzymes are generally inherited in an autosomal fashion because there are more non-X chromosomes than X-chromosomes, and a recessive fashion because the enzymes from the unaffected genes are generally sufficient to prevent symptoms in carriers.

Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life.

In some enzymes, no amino acids are directly involved in catalysis; instead, the enzyme contains sites to bind and orient catalytic cofactors.

The redox reactions of nicotinamide adenine dinucleotide.

Nicotinamide adenine dinucleotide

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The redox reactions of nicotinamide adenine dinucleotide.
UV absorption spectra of NAD and NADH.
Some metabolic pathways that synthesize and consume NAD in vertebrates. The abbreviations are defined in the text.
Salvage pathways use three precursors for NAD+.
Rossmann fold in part of the lactate dehydrogenase of Cryptosporidium parvum, showing NAD in red, beta sheets in yellow, and alpha helices in purple.
In this diagram, the hydride acceptor C4 carbon is shown at the top. When the nicotinamide ring lies in the plane of the page with the carboxy-amide to the right, as shown, the hydride donor lies either "above" or "below" the plane of the page. If "above" hydride transfer is class A, if "below" hydride transfer is class B.
A simplified outline of redox metabolism, showing how NAD and NADH link the citric acid cycle and oxidative phosphorylation.
The structure of cyclic ADP-ribose.
Arthur Harden, co-discoverer of NAD

Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism.

This nucleotide contains the five-carbon sugar deoxyribose (at center), a nucleobase called adenine (upper right), and one phosphate group (left). The deoxyribose sugar joined only to the nitrogenous base forms a <u title="Nucleotide">Deoxyribonucleoside called deoxyadenosine, whereas the whole structure along with the phosphate group is a <u title="Deoxyadenosine monophosphate" href="deoxyadenosine monophosphate">nucleotide, a constituent of DNA with the name deoxyadenosine monophosphate.

Nucleotide

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Nucleotides are organic molecules consisting of a nucleoside and a phosphate.

Nucleotides are organic molecules consisting of a nucleoside and a phosphate.

This nucleotide contains the five-carbon sugar deoxyribose (at center), a nucleobase called adenine (upper right), and one phosphate group (left). The deoxyribose sugar joined only to the nitrogenous base forms a <u title="Nucleotide">Deoxyribonucleoside called deoxyadenosine, whereas the whole structure along with the phosphate group is a <u title="Deoxyadenosine monophosphate" href="deoxyadenosine monophosphate">nucleotide, a constituent of DNA with the name deoxyadenosine monophosphate.
Showing the arrangement of nucleotides within the structure of nucleic acids: At lower left, a monophosphate nucleotide; its nitrogenous base represents one side of a base-pair. At the upper right, four nucleotides form two base-pairs: thymine and adenine (connected by double hydrogen bonds) and guanine and cytosine (connected by triple hydrogen bonds). The individual nucleotide monomers are chain-joined at their sugar and phosphate molecules, forming two 'backbones' (a double helix) of nucleic acid, shown at upper left.
Structural elements of three nucleo tides —where one-, two- or three-phosphates are attached to the nucleo side (in yellow, blue, green) at center: 1st, the nucleotide termed as a nucleoside mono phosphate is formed by adding a phosphate (in red); 2nd, adding a second phosphate forms a nucleoside di phosphate; 3rd, adding a third phosphate results in a nucleoside tri phosphate. + The nitrogenous base (nucleobase) is indicated by "Base" and "glycosidic bond" (sugar bond). All five primary, or canonical, bases—the purines and pyrimidines—are sketched at right (in blue).
The synthesis of UMP. The color scheme is as follows: enzymes, <span style="color: rgb(219,155,36);">coenzymes, <span style="color: rgb(151,149,45);">substrate names , <span style="color: rgb(128,0,0);">inorganic molecules
The synthesis of IMP. The color scheme is as follows: enzymes, <span style="color: rgb(219,155,36);">coenzymes, <span style="color: rgb(151,149,45);">substrate names , <span style="color: rgb(227,13,196);">metal ions , <span style="color: rgb(128,0,0);">inorganic molecules

Nucleotides also play a central role in metabolism at a fundamental, cellular level.

They provide chemical energy—in the form of the nucleoside triphosphates, adenosine triphosphate (ATP), guanosine triphosphate (GTP), cytidine triphosphate (CTP) and uridine triphosphate (UTP)—throughout the cell for the many cellular functions that demand energy, including: amino acid, protein and cell membrane synthesis, moving the cell and cell parts (both internally and intercellularly), cell division, etc. In addition, nucleotides participate in cell signaling (cyclic guanosine monophosphate or cGMP and cyclic adenosine monophosphate or cAMP), and are incorporated into important cofactors of enzymatic reactions (e.g. coenzyme A, FAD, FMN, NAD, and NADP+).

Interactive animation of the structure of ATP

Adenosine triphosphate

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Organic compound and hydrotrope that provides energy to drive many processes in living cells, such as muscle contraction, nerve impulse propagation, condensate dissolution, and chemical synthesis.

Organic compound and hydrotrope that provides energy to drive many processes in living cells, such as muscle contraction, nerve impulse propagation, condensate dissolution, and chemical synthesis.

Interactive animation of the structure of ATP
The cycles of synthesis and degradation of ATP; 2 and 1 represent input and output of energy, respectively.
This image shows a 360-degree rotation of a single, gas-phase magnesium-ATP chelate with a charge of −2. The anion was optimized at the UB3LYP/6-311++G(d,p) theoretical level and the atomic connectivity modified by the human optimizer to reflect the probable electronic structure.
An example of the Rossmann fold, a structural domain of a decarboxylase enzyme from the bacterium Staphylococcus epidermidis with a bound flavin mononucleotide cofactor.

When consumed in metabolic processes, it converts either to adenosine diphosphate (ADP) or to adenosine monophosphate (AMP).

It is also a precursor to DNA and RNA, and is used as a coenzyme.

Dihydrofolate reductase from E. coli with its two substrates dihydrofolate (right) and NADPH (left), bound in the active site. The protein is shown as a ribbon diagram, with alpha helices in red, beta sheathes in yellow and loops in blue. Generated from 7DFR.

Enzyme kinetics

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Study of the rates of enzyme-catalysed chemical reactions.

Study of the rates of enzyme-catalysed chemical reactions.

Dihydrofolate reductase from E. coli with its two substrates dihydrofolate (right) and NADPH (left), bound in the active site. The protein is shown as a ribbon diagram, with alpha helices in red, beta sheathes in yellow and loops in blue. Generated from 7DFR.
As larger amounts of substrate are added to a reaction, the available enzyme binding sites become filled to the limit of V_\max. Beyond this limit the enzyme is saturated with substrate and the reaction rate ceases to increase.
Progress curve for an enzyme reaction. The slope in the initial rate period is the initial rate of reaction v. The Michaelis–Menten equation describes how this slope varies with the concentration of substrate.
Lineweaver–Burk or double-reciprocal plot of kinetic data, showing the significance of the axis intercepts and gradient.
Random-order ternary-complex mechanism for an enzyme reaction. The reaction path is shown as a line and enzyme intermediates containing substrates A and B or products P and Q are written below the line.
Saturation curve for an enzyme reaction showing sigmoid kinetics.
Pre-steady state progress curve, showing the burst phase of an enzyme reaction.
Kinetic scheme for reversible enzyme inhibitors.
The energy variation as a function of reaction coordinate shows the stabilisation of the transition state by an enzyme.

Studying an enzyme's kinetics in this way can reveal the catalytic mechanism of this enzyme, its role in metabolism, how its activity is controlled, and how a drug or a modifier (inhibitor or activator) might affect the rate.

These measurements either use changes in the fluorescence of cofactors during an enzyme's reaction mechanism, or of fluorescent dyes added onto specific sites of the protein to report movements that occur during catalysis.

Yeast

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Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom.

Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom.

Yeast ring used by Swedish farmhouse brewers in the 19th century to preserve yeast between brewing sessions.
Bubbles of carbon dioxide forming during beer-brewing
Yeast in a bottle during sparkling wine production at Schramsberg Vineyards, Napa
A block of compressed fresh yeast
Active dried yeast, a granulated form in which yeast is commercially sold
Diagram showing a yeast cell
Gram stain of Candida albicans from a vaginal swab. The small oval chlamydospores are 2–4 µm in diameter.
A photomicrograph of Candida albicans showing hyphal outgrowth and other morphological characteristics

This ethanol is almost always produced by fermentation – the metabolism of carbohydrates by certain species of yeasts under anaerobic or low-oxygen conditions.

Nutritional yeast in particular is naturally low in fat and sodium and a source of protein and vitamins as well as other minerals and cofactors required for growth.

A bottle of B-complex vitamin pills

Vitamin

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A bottle of B-complex vitamin pills
Calcium combined with vitamin D (as calciferol) supplement tablets with fillers.
Jack Drummond's single-paragraph article in 1920 which provided structure and nomenclature used today for vitamins

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.

The B complex vitamins function as enzyme cofactors (coenzymes) or the precursors for them.

Molar volume vs. pressure for α iron at room temperature

Iron

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Chemical element with symbol Fe and atomic number 26.

Chemical element with symbol Fe and atomic number 26.

Molar volume vs. pressure for α iron at room temperature
Low-pressure phase diagram of pure iron
Magnetization curves of 9 ferromagnetic materials, showing saturation. 1.Sheet steel, 2.Silicon steel, 3.Cast steel, 4.Tungsten steel, 5.Magnet steel, 6.Cast iron, 7.Nickel, 8.Cobalt, 9.Magnetite
A polished and chemically etched piece of an iron meteorite, believed to be similar in composition to the Earth's metallic core, showing individual crystals of the iron-nickel alloy (Widmanstatten pattern)
Ochre path in Roussillon.
Banded iron formation in McKinley Park, Minnesota.
Pourbaix diagram of iron
Hydrated iron(III) chloride (ferric chloride)
Comparison of colors of solutions of ferrate (left) and permanganate (right)
Blue-green iron(II) sulfate heptahydrate
The two enantiomorphs of the ferrioxalate ion
Crystal structure of iron(II) oxalate dihydrate, showing iron (gray), oxygen (red), carbon (black), and hydrogen (white) atoms.
Blood-red positive thiocyanate test for iron(III)
Iron penta- carbonyl
Prussian blue
Iron harpoon head from Greenland. The iron edge covers a narwhal tusk harpoon using meteorite iron from the Cape York meteorite, one of the largest iron meteorites known.
The symbol for Mars has been used since antiquity to represent iron.
The iron pillar of Delhi is an example of the iron extraction and processing methodologies of early India.
Iron sickle from Ancient Greece.
Coalbrookdale by Night, 1801. Blast furnaces light the iron making town of Coalbrookdale.
"Gold gab ich für Eisen" – "I gave gold for iron". German-American brooch from WWI.
Iron powder
Iron furnace in Columbus, Ohio, 1922
17th century Chinese illustration of workers at a blast furnace, making wrought iron from pig iron
How iron was extracted in the 19th century
This heap of iron ore pellets will be used in steel production.
A pot of molten iron being used to make steel
Iron-carbon phase diagram
Photon mass attenuation coefficient for iron.
Structure of Heme b; in the protein additional ligand(s) would be attached to Fe.
A heme unit of human carboxyhemoglobin, showing the carbonyl ligand at the apical position, trans to the histidine residue

These two proteins play essential roles in vertebrate metabolism, respectively oxygen transport by blood and oxygen storage in muscles.

Metalloproteins are a group of proteins with metal ion cofactors.

Methanogen

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Methanogens are microorganisms that produce methane as a metabolic byproduct in hypoxic conditions.

Different methanogenic reactions are catalyzed by unique sets of enzymes and coenzymes.