Simple sugars have actually a high glycemic index, are much more rapidly digested, and also produce greater glycemic and insulinemic responses.

You are watching: Which of the following is a monosaccharide

From: Cardiovascular Therapeutics (Third Edition), 2007

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Simple street are single molecules, conversely, more complex sugars are much more than one molecule joined with each other by chemical bonds. Street are made up of carbon, oxygen and hydrogen; no nitrogen, other than for amino sugars. The simplest sugars room monosaccharides. Six-carbon monosaccharides room prevalent but monosaccharides deserve to have from 3 come 7 carbons in their structures (3 carbons, triose; 4 carbons, tetrose; 5 carbons, pentose, 6 carbons, hexose and 7 carbons, heptose). The hexoses room common and also important. Glucose is the many representative member that the hexoses. The structure of glucose is shown in Fig. 6.17 in a simple stick model (Fischer projection) and also how that is closed into a ring framework (Haworth projection). Sugars contain chiral carbons which are those carbons having actually 4 various substituents. If 2 that the substituents of a carbon atom space the same (e.g., double bond come an oxygen or single bonds come 2 hydroxyls or come 2 hydrogens) that carbon is achiral. Inspecting the open up stick design of glucose, because that example, there are 4 chiral centers in ~ C2, C3, C4, and C5. The variety of chiral carbons identify the variety of stereoisomers, thus, because that an aldotetrose through 2 chiral centers, the number of stereoisomers is 22 or 4 stereoisomers; because that glucose through 4 chiral centers, it has actually 24 or 16 stereoisomers.

Figure 6.17. Stick version of glucose. Carbon 1 is the optimal carbon and also the number is numbered proceeds in the direction of the bottom; the lowest is carbon 6. The ring is closed through a nucleophilic addition between the C1 aldehyde and the C5 hydroxyl. The proton top top C5 migrates come the oxygen that C1.

There room a number of simple sugars varying from 3 carbons (triose) to 7 carbons (heptose), although sugars of six-carbon length (hexose) are considered here. A five-carbon street is a pentose and a four-carbon street is a tetrose. Sugars room either aldoses or ketoses; an aldose sugar has an aldehyde group (e.g., the C1 that d-glucose seen plainly in the open up stick model); a ketose has a ketone team (e.g., the C2 of d-fructose plainly seen in the open up stick model). The an easy stick frameworks (Fischer projections) are shown in Fig. 6.18.

Figure 6.18. Monosaccharides, either organic or synthetic showing aldose street (top) and also ketose street (bottom).

The number of chiral carbons determines the number of stereoisomers. The 4 stereoisomers of a tetrose are presented in Fig. 6.19.

In the process of cyclization of glucose, the carbon 1 carbonyl have the right to be struck from two sides generating the opportunity of α- or β-forms, through the rearrangement the a proton in the process as presented in Fig. 6.20.

Figure 6.20. D-Glucose, in the Fischer projection, is convert to the Haworth forecast with glucose as a five-member ring structure (pyranose). The special lines at the bottom of the ring structures indicate expansion of that component of the structure outside from the page toward the reader.

The α- and also β-forms in the ringed form of glucose space named based upon the place of the hydroxyl on carbon-1 as presented in Fig. 6.21.

β-d-glucose has actually the C-1 hydroxyl top top the left and also α-d-glucose has the C-1 hydroxyl ~ above the right. “D” refers to dextro, or best (as through the amino acids). As soon as the street is in the kind of a ring, the carbon bonds deserve to bend right into either among two forms: a “chair” configuration or a “boat” configuration. One form may be favored end the other, relying on hydroxyl substituents in the ring. The general develops of these frameworks for a six-carbon street skeleton are presented in Fig. 6.22.

Figure 6.22. (A) allowed configurations because that six-member sugars. (B) alternating chair conformations for 6-membered sugars: one “up” carbon (e.g., axial) presented on right (circled in red) and a rotated version showing the axial carbon together “down” top top left (circled in red). α- and β-Forms are figured out by the position of the hydroxyl group attached to the anomeric carbon (asterisk) and also the CH2OH attached come the other carbon alongside the ether. α-Carbohydrates have actually a cis configuration between the OH team attached to the anomeric carbon and the CH2OH group (circled in blue). The five group and the CH2OH group are top top opposite sides of the ring. β-Carbohydrates have actually a trans configuration in between the OH group attached come the anomeric carbon and the CH2OH group (circled in blue). The oh group and also the CH2OH group are on the very same side of the ring.

Sugar rings do not kind a level ring prefer benzene; the benzene ring consists of three twin bonds the are shorter (1.34 Å) 보다 carbon-to-carbon solitary bonds (1.40 Å). An easy sugars have the right to be represented in 4 ways (not including the boat structure) as shown in Fig. 6.23.

Figure 6.23. Four various ways of composing the structures for the hexose, glucose, or because that the pentose, ribose, including the chair configuration.

Disaccharides are created using the α- (axial shortcut down) or the β-(equatorial bond up) hydroxyl ~ above the ring as displayed in Fig. 6.24. The place of a specific substituent (in this case, hydroxyl group) together up or under stems native the stereoisomeric center (anomeric carbon) that the sugar. In the ring develops (chair, e.g.), the anomeric carbon deserve to be located as the carbon next to the ring oxygen not attached to CH2OH. In the chair configuration, one hydrogen on every carbon is equatorial and also one hydrogen is axial. The equatorial hydrogens radiate from about the ring if the axial hydrogens point along one axis or parallel come an axis; axial bonds room upwards or downwards follow me an axis with the facility of the ring. Additionally the hydroxyl substituent that the anomeric carbon can be either up or down. If that is under (axial), the street is in the α form: if that is up (equatorial), the sugar is in the β form (e.g., α-d-glucopyranose or β-d-glucopyranose).

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Figure 6.24. Monosaccharides connect using α-hydroxyls or β-hydroxyls on the ring structure to create some naturally developing disaccharides. In lactose, the glucose moiety deserve to open and duty as a reducing sugar, whereas, in sucrose both rings space locked making the a nonreducing sugar. The glucose moiety ~ above the left the d-maltose cannot open, whereas the glucose moiety on the appropriate is able to open making maltose a reducing sugar. Maltose is the repeating street unit in starch.