Cofactor (biochemistry)

The succinate dehydrogenase complex showing several cofactors, including flavin, iron–sulfur centers, and heme.
A simple [Fe2S2] cluster containing two iron atoms and two sulfur atoms, coordinated by four protein cysteine residues.
The redox reactions of nicotinamide adenine dinucleotide.

Non-protein chemical compound or metallic ion that is required for an enzyme's role as a catalyst .

- Cofactor (biochemistry)
The succinate dehydrogenase complex showing several cofactors, including flavin, iron–sulfur centers, and heme.

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The redox reactions of nicotinamide adenine dinucleotide.

Nicotinamide adenine dinucleotide

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.

Structure of coenzyme A: 1: 3′-phosphoadenosine. 2: diphosphate, organophosphate anhydride. 3: pantoic acid. 4: β-alanine. 5: cysteamine.

Coenzyme A

Structure of coenzyme A: 1: 3′-phosphoadenosine. 2: diphosphate, organophosphate anhydride. 3: pantoic acid. 4: β-alanine. 5: cysteamine.
Details of the biosynthetic pathway of CoA synthesis from pantothenic acid.
Some of the sources that CoA comes from and uses in the cell.

Coenzyme A (CoA, SHCoA, CoASH) is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle.

Reaction of FAD to form FADH2

Flavin adenine dinucleotide

Reaction of FAD to form FADH2
Approximate absorption spectrum for FAD
Mechanism 1. Hydride transfer occurs by addition of H+ and 2 e−
Mechanism 2. Hydride transfer by abstraction of hydride from NADH
Mechanism 3. Radical formation by electron abstraction
Mechanism 4. The loss of hydride to electron deficient R group
Mechanism 5. Use of nucleophilic addition to break R1-R2 bond
Mechanism 6. Carbon radical reacts with O2 and acid to form H2O2
Riboflavin
FADH{{sub|2}}

In biochemistry, flavin adenine dinucleotide (FAD) is a redox-active coenzyme associated with various proteins, which is involved with several enzymatic reactions in metabolism.

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

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.

Interactive animation of the structure of ATP

Adenosine triphosphate

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.

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

Summary of aerobic respiration

Glycolysis

Metabolic pathway that converts glucose , into pyruvic acid (CH3COCO2H).

Metabolic pathway that converts glucose , into pyruvic acid (CH3COCO2H).

Summary of aerobic respiration
Summary of the 10 reactions of the glycolysis pathway
Glycolysis pathway overview.
Eduard Buchner. Discovered cell-free fermentation.
Otto Meyerhof. One of the main scientists involved in completing the puzzle of glycolysis
Yeast hexokinase B
Bacillus stearothermophilus phosphofructokinase
Yeast pyruvate kinase

Arthur Harden and William Young along with Nick Sheppard determined, in a second experiment, that a heat-sensitive high-molecular-weight subcellular fraction (the enzymes) and a heat-insensitive low-molecular-weight cytoplasm fraction (ADP, ATP and NAD+ and other cofactors) are required together for fermentation to proceed.

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Pyruvate dehydrogenase

Enzyme that catalyzes the reaction of pyruvate and a lipoamide to give the acetylated dihydrolipoamide and carbon dioxide.

Enzyme that catalyzes the reaction of pyruvate and a lipoamide to give the acetylated dihydrolipoamide and carbon dioxide.

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Simplified mechanism for pyruvate dehydrogenase reaction. The TPP coenzyme is shown with abbreviated substituents.
Pyruvate dehydrogenase E1 subunit of E. coli. Colors represent different chains. Structure determined by Arjunan et al. Biochemistry 2002.  Created with PyMol.
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The conversion requires the coenzyme thiamine pyrophosphate.

A bottle of B-complex vitamin pills

Vitamin

Organic molecule that is an essential micronutrient which an organism needs in small quantities for the proper functioning of its metabolism.

Organic molecule that is an essential micronutrient which an organism needs in small quantities for the proper functioning of its metabolism.

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

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

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

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

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+).

A block of electrolytically refined cobalt (99.9% purity) cut from a large plate

Cobalt

Chemical element with the symbol Co and atomic number 27.

Chemical element with the symbol Co and atomic number 27.

A block of electrolytically refined cobalt (99.9% purity) cut from a large plate
Cobalt(II) chloride hexahydrate
Structure of tetrakis(1-norbornyl)cobalt(IV)
Early Chinese blue and white porcelain, manufactured c. 1335
Cobalt ore
World production trend
Cobalt prices February and March 2021 (USD$ per ton)
Cobalt prices 2016 to 2021 5 years (USD$ per ton)
Cobalt blue glass
Cobalt-colored glass
alt=chemical diagram of cobalamin molecule|Cobalamin
alt=two cobalt-deficient sheep facing away from camera|Cobalt-deficient sheep

Cobalt is the active center of a group of coenzymes called cobalamins.