A report on 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}}

Redox-active coenzyme associated with various proteins, which is involved with several enzymatic reactions in metabolism.

- Flavin adenine dinucleotide
Reaction of FAD to form FADH2

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Overall
Overview of the citric acid cycle

Citric acid cycle

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Series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

Series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

Overview of the citric acid cycle
Structural diagram of acetyl-CoA: The portion in blue, on the left, is the acetyl group; the portion in black is coenzyme A.

The overall yield of energy-containing compounds from the citric acid cycle is three NADH, one FADH2, and one GTP.

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.

NADH and FADH2 are recycled (to NAD+ and FAD, respectively) by oxidative phosphorylation, generating additional ATP.

There are 18 key atoms in isoalloxazine that make up its characteristic three-ring structure. The R-group varies and differentiates various flavins.

Flavin group

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Common name for a group of organic compounds based on pteridine, formed by the tricyclic heterocycle isoalloxazine.

Common name for a group of organic compounds based on pteridine, formed by the tricyclic heterocycle isoalloxazine.

There are 18 key atoms in isoalloxazine that make up its characteristic three-ring structure. The R-group varies and differentiates various flavins.
Riboflavin
Equilibrium between the oxidized (left) and totally reduced (right) forms of flavin.
FAD
FMN

The flavin moiety is often attached with an adenosine diphosphate to form flavin adenine dinucleotide (FAD), and, in other circumstances, is found as flavin mononucleotide (or FMN), a phosphorylated form of riboflavin.

Typical eukaryotic cell

Cellular respiration

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Set of metabolic reactions and processes that take place in the cells of organisms to convert chemical energy from nutrients into adenosine triphosphate , and then release waste products.

Set of metabolic reactions and processes that take place in the cells of organisms to convert chemical energy from nutrients into adenosine triphosphate , and then release waste products.

Typical eukaryotic cell
Out of the cytoplasm it goes into the Krebs cycle with the acetyl CoA. It then mixes with CO2 and makes 2 ATP, NADH, and FADH. From there the NADH and FADH go into the NADH reductase, which produces the enzyme. The NADH pulls the enzyme's electrons to send through the electron transport chain. The electron transport chain pulls H+ ions through the chain. From the electron transport chain, the released hydrogen ions make ADP for an result of 32 ATP. O2 provides most of the energy for the process and combines with protons and the electrons to make water. Lastly, ATP leaves through the ATP channel and out of the mitochondria.
Stoichiometry of aerobic respiration and most known fermentation types in eucaryotic cell. Numbers in circles indicate counts of carbon atoms in molecules, C6 is glucose C6H12O6, C1 carbon dioxide CO2. Mitochondrial outer membrane is omitted.

The products of this process are carbon dioxide and water, and the energy transferred is used to break bonds in ADP to add a third phosphate group to form ATP (adenosine triphosphate), by substrate-level phosphorylation, NADH and FADH2

Two mitochondria from mammalian lung tissue displaying their matrix and membranes as shown by electron microscopy

Mitochondrion

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Double-membrane-bound organelle found in most eukaryotic organisms.

Double-membrane-bound organelle found in most eukaryotic organisms.

Two mitochondria from mammalian lung tissue displaying their matrix and membranes as shown by electron microscopy
Simplified structure of a mitochondrion.
Cross-sectional image of cristae in a rat liver mitochondrion to demonstrate the likely 3D structure and relationship to the inner membrane
Electron transport chain in the mitochondrial intermembrane space
Transmission electron micrograph of a chondrocyte, stained for calcium, showing its nucleus (N) and mitochondria (M).
Typical mitochondrial network (green) in two human cells (HeLa cells)
Model of the yeast multimeric tethering complex, ERMES
Evolution of MROs
The circular 16,569 bp human mitochondrial genome encoding 37 genes, i.e., 28 on the H-strand and 9 on the L-strand.

The citric acid cycle oxidizes the acetyl-CoA to carbon dioxide, and, in the process, produces reduced cofactors (three molecules of NADH and one molecule of FADH2) that are a source of electrons for the electron transport chain, and a molecule of GTP (which is readily converted to an ATP).

The succinate dehydrogenase complex showing several cofactors, including flavin, iron–sulfur centers, and heme.

Cofactor (biochemistry)

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

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

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.

For example, the multienzyme complex pyruvate dehydrogenase at the junction of glycolysis and the citric acid cycle requires five organic cofactors and one metal ion: loosely bound thiamine pyrophosphate (TPP), covalently bound lipoamide and flavin adenine dinucleotide (FAD), cosubstrates nicotinamide adenine dinucleotide (NAD+) and coenzyme A (CoA), and a metal ion (Mg2+).

Chemical structure

Riboflavin

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Vitamin found in food and sold as a dietary supplement.

Vitamin found in food and sold as a dietary supplement.

Chemical structure
Cultures of Micrococcus luteus growing on pyridine (left) and succinic acid (right). The pyridine culture has turned yellow from the accumulation of riboflavin.

It is essential to the formation of two major coenzymes, flavin mononucleotide and flavin adenine dinucleotide.

The electron transport chain in the mitochondrion is the site of oxidative phosphorylation in eukaryotes. The NADH and succinate generated in the citric acid cycle are oxidized, which releases the energy of oxygen to power ATP synthase.

Electron transport chain

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Series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H+ ions) across a membrane.

Series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H+ ions) across a membrane.

The electron transport chain in the mitochondrion is the site of oxidative phosphorylation in eukaryotes. The NADH and succinate generated in the citric acid cycle are oxidized, which releases the energy of oxygen to power ATP synthase.
Photosynthetic electron transport chain of the thylakoid membrane.
Depiction of ATP synthase, the site of oxidative phosphorylation to generate ATP.

The energy released by reactions of oxygen and reduced compounds such as cytochrome c and (indirectly) NADH and FADH is used by the electron transport chain to pump protons into the intermembrane space, generating the electrochemical gradient over the inner mitochondrial membrane.

Adenine structure, with standard numbering of positions in red.

Adenine

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Nucleobase (a purine derivative).

Nucleobase (a purine derivative).

Adenine structure, with standard numbering of positions in red.
Adenine on Crick and Watson's DNA molecular model, 1953. The picture is shown upside down compared to most modern drawings of adenine, such as those used in this article.

Its derivatives have a variety of roles in biochemistry including cellular respiration, in the form of both the energy-rich adenosine triphosphate (ATP) and the cofactors nicotinamide adenine dinucleotide (NAD), flavin adenine dinucleotide (FAD) and Coenzyme A.

Solution NMR structure of protein NMA1147 from Neisseria meningitidis. Northeast structural genomics consortium target mr19

Succinate dehydrogenase

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Enzyme complex, found in many bacterial cells and in the inner mitochondrial membrane of eukaryotes.

Enzyme complex, found in many bacterial cells and in the inner mitochondrial membrane of eukaryotes.

Solution NMR structure of protein NMA1147 from Neisseria meningitidis. Northeast structural genomics consortium target mr19
Image 5: Subunits of succinate dehydrogenase
Image 6: E2 Succinate oxidation mechanism.
Image 7: E1cb Succinate oxidation mechanism.
Image 8: Ubiquinone reduction mechanism.
Image 9: Electron carriers of the SQR complex. FADH2, iron-sulfur centers, heme b, and ubiquinone.

SdhA contains a covalently attached flavin adenine dinucleotide (FAD) cofactor and the succinate binding site and SdhB contains three iron-sulfur clusters: [2Fe-2S], [4Fe-4S], and [3Fe-4S].