Nutrition Guide

The formose reaction is of importance to the question of the origin of life as it is a path from simple formaldehyde to complex sugars like ribose and from there to RNA. In one experiment simulating early Earth conditions, pentoses formed from mixtures of formaldehyde, glyceraldehyde, and borate minerals such as colemanite Ca2B6O115H2O or kernite Na2B4O7.[4] Adding to the interest in the formose reaction is the fact that both formaldehyde and glycolaldehyde have been observed spectroscopically in outer space.

Carbohydrates are reactants in many organic reactions. For example: Carbohydrate acetalisation Cyanohydrin reaction Lobry-de Bruyn-van Ekenstein transformation Amadori rearrangement Nef reaction Wohl degradation Koenigs-Knorr reaction

Photosynthetic reaction centre proteins are main protein components of photosynthetic reaction centers of bacteria and plants.

The reaction catalyzed by this enzyme in the citric acid cycle is: ?-ketoglutarate + NAD+ + CoA ? Succinyl CoA + CO2 + NADHThis reaction proceeds in three steps: decarboxylation of ?-ketoglutarate, reduction of NAD+ to NADH, and subsequent transfer to CoA, which forms the end product, succinyl CoA. ?G°' for this reaction is -7.2 kcal mol-1. The energy needed for this oxidation is conserved in the formation of a thioester bond of succinyl CoA.

The enzyme first catalyzes nucleophilic attack on the ?-phosphate of ATP to form pyrophosphate and an acyl chain linked to AMP. The next step is formation of an activated thioester bond between the fatty acyl chain and Coenzyme A.This two-step reaction is freely reversible and its equilibrium lies near 1. To drive the reaction forward, the reaction is coupled to a strongly exergonic hydrolysis reaction: the enzyme inorganic pyrophosphatase cleaves the pyrophosphate liberated from ATP to two phosphate ions. Thus the net reaction becomes:

In biochemistry, a lyase is an enzyme that catalyzes the breaking of various chemical bonds by means other than hydrolysis and oxidation, often forming a new double bond or a new ring structure. For example, an enzyme that catalyzed this reaction would be a lyase: ATP ? cAMP + PPi Lyases differ from other enzymes in that they only require one substrate for the reaction in one direction, but two substrates for the reverse reaction.

The plot provides a useful graphical method for analysis of the Michaelis-Menten equation: Taking the reciprocal gives where V is the reaction velocity (the reaction rate), Km is the Michaelis-Menten constant, Vmax is the maximum reaction velocity, and [S] is the substrate concentration.

In KYNU reaction, PLP facilitates C?-C? bond cleavage. The reaction follows the same steps as the transamination reaction but does not hydrolyze the tautomerized Schiff base. The proposed reaction mechanism involves an attack of an enzyme nucleophile on the carbonyl carbon (C?) of the tautomerized 3hKyn-PLP Schiff base. This is followed by C?-C? bond cleavage to generate an acyl-enzyme intermediate together with a tautomerized Ala-PLP adduct. Hydrolysis of the acyl-enzyme then yields 3hAnt.

Fischer glycosidation (or Fischer glycosylation) refers to the formation of a glycoside by the reaction of an aldose or ketose with an alcohol in the presence of an acid catalyst. The reaction is named after the German chemist, Emil Hermann Fischer, winner of the Nobel Prize in chemistry, 1902, who developed this method between 1893 and 1895.[1][2][3] Commonly, the reaction is performed using a solution or suspension of the carbohydrate in the alcohol as the solvent. The carbohydrate is usually completely unprotected. The Fischer glycosidation reaction is an equilibrium process and can lead to a mixture of ring size isomers, and

The reaction rate V is the number of reactions per second catalyzed per mole of the enzyme. The reaction rate increases with increasing substrate concentration [S], asymptotically approaching the maximum rate Vmax. There is therefore no clearly-defined substrate concentration at which the enzyme can be said to be saturated with substrate. A more appropriate measure to characterize an enzyme is the substrate concentration at which the reaction rate reaches half of its maximum value (Vmax/2). This concentration can be shown to be equal to the Michaelis constant (KM).

A photosynthetic reaction center is a complex of three types of protein that is the site where molecular excitations originating from sunlight are transformed into a series of electron-transfer reactions. The reaction center proteins bind functional co-factors, chromophores or pigments such as chlorophyll and pheophytin molecules. These absorb light, promoting an electron to a higher energy level within a pigment. The free energy created is used to reduce a chain of electron acceptors which have subsequently lowered redox-potentials, and is critical for the production of chemical energy during photosynthesis. Reaction centers are present in all green plants and in many bacteria

Chalcones can be prepared by an aldol condensation between a benzaldehyde and an acetophenone in the presence of sodium hydroxide as a catalyst.This reaction has been found to work without any solvent at all - a solid-state reaction.[5] The reaction between substituted benzaldehydes and acetophenones has been used to demonstrate green chemistry in undergraduate chemistry education.[6] In a study investigating green chemistry synthesis, chalcones were also synthesized from the same starting materials in high temperature water (200 to 350 °C).[7

In the tryptophan metabolism pathway, N- Acetylserotonin O-methyltransferase catalyzes two separate reactions. The first reaction shown (Figure 2) is the reaction of N-acetyl-serotonin to N-acetyl-5-methoxy-tryptamine. S-adenosyl-L-methionine is used as a substrate and is converted to S-adenosyl-L-homocysteine. [7] Figure 2: Reaction catalyzed by N- Acetylserotonin O-methyltransferase Figure 3 is the same reaction as above, but the figure provides a clearer picture of how the reactant proceeds to product using N-Acetylserotonin O-methyltransferase in addition to the substrate. [4] Figure 3: Role of N- Acetylserotonin O-methyltransferase The second reaction (Figure 4) catalyzed by N-Acetylserotonin O-methyltransferase in the tryptophan metabolism pathway is: S-Adenosyl-L-methionine + 5-Hydroxyindoleacetate ? S-Adenosyl-L-homocysteine +

Fructose undergoes the Maillard reaction, non-enzymatic browning, with amino acids. Because fructose exists to a greater extent in the open-chain form than does glucose, the initial stages of the Maillard reaction occurs more rapidly than with glucose. Therefore, fructose potentially may contribute to changes in food palatability, as well as other nutritional effects, such as excessive browning, volume and tenderness reduction during cake preparation, and formation of mutagenic compounds. [4]

General qualitative reaction for ketoses is Seliwanoff's test.

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