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The table shows all aldoses with 3 to 6 carbon atoms, and a few ketoses. For chiral molecules, only the ' D-' form (with the next-to-last hydroxyl on the right side) is shown; the corresponding forms have mirror-image structures. Some of these monosaccharides are only synthetically prepared in the laboratory and not found in nature.
Monosaccharides can be classified by the number x of carbon atoms they contain: triose (3), tetrose (4), pentose (5), hexose (6), heptose (7), and so on. Glucose, used as an energy source and for the synthesis of starch, glycogen and cellulose, is a hexose. Ribose and deoxyribose (in RNA and DNA, respectively) are pentose sugars.
Glucose circulates in the blood of animals as blood sugar. [6] [8] The naturally occurring form is d-glucose, while its stereoisomer l-glucose is produced synthetically in comparatively small amounts and is less biologically active. [8] Glucose is a monosaccharide containing six carbon atoms and an aldehyde group, and is therefore an aldohexose ...
Many chiral molecules have point chirality, namely a single chiral stereogenic center that coincides with an atom. This stereogenic center usually has four or more bonds to different groups, and may be carbon (as in many biological molecules), phosphorus (as in many organophosphates ), silicon, or a metal (as in many chiral coordination ...
The minimum number of carbon atoms in a backbone needed to form a molecule that is still considered a carbohydrate is 3, and carbohydrates with three carbon atoms are called trioses. The only aldotriose is glyceraldehyde , which has one chiral stereocenter with 2 possible enantiomers, D - and L -glyceraldehyde.
In stereochemistry, an asymmetric carbon is a carbon atom that is bonded to four different types of atoms or groups of atoms. [1] [2] The four atoms and/or groups attached to the carbon atom can be arranged in space in two different ways that are mirror images of each other, and which lead to so-called left-handed and right-handed versions (stereoisomers) of the same molecule.
Fischer projection of D-Glyceraldehyde.Projection of a tetrahedral molecule onto a planar surface. Visualizing a Fischer projection. In chemistry, the Fischer projection, devised by Emil Fischer in 1891, is a two-dimensional representation of a three-dimensional organic molecule by projection.
Chiral centres are designated R or S. If the 3 groups projecting towards you are arranged clockwise from highest priority to lowest priority, that centre is designated R. If counterclockwise, the centre is S. Priority is based on atomic number: atoms with higher atomic number are higher priority.