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Ribose

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Ribose
Ribose
Systematic name Ribose
Chemical formula C5H10O5
Molecular mass 150.13 g/mol
Melting point 90 - 95 °C
CAS number [50-69-1]
Disclaimer and references

Ribose is a simple carbohydrate (sugar) known as a monosaccharide. It is five-carbon compound primarily used as a component of the RNA used for genetic transcription, and as such is vitally important to all living creatures. It is not, however, an essential nutrient, since it can be made in the body from other substances, such as glucose.[1] It is a component of ATP, NADH, and several other chemicals that are critical to metabolism. It is primarily seen as D-ribose, and is an aldopentose. D-ribose is a naturally occurring sugar found in all living cells, as well as in RNA-containing viruses. It has the chemical formula C5H10O5, and was discovered in 1905 by Phoebus Levene.[2]

D-Ribose

D-Ribose

D-ribose is very essential for life. Some of the most important biological molecules contain D-ribose, including ATP, and all the nucleotides and nucleotide coenzymes and all forms of RNA. D-ribose, in the form of ribonucleoside diphosphates, is converted to deoxyribonucleoside diphosphates, precursor molecules for DNA.[3]

Since D-ribose is ubiquitous in living matter, it is ingested in our diets. Such nutritional substances as brewers yeast are rich in RNA and are thus rich sources of D-ribose. Some recent research suggests that supraphysiological amounts of this sugar may have cardioprotective effects, particularly for the ischemic heart.

D-ribose is a sweet, solid, water-soluble substance that is also known as alpha-D-ribofuranoside. Supplemental D-ribose is produced from the fermentation of corn syrup.[4] Ribose is a five-carbon sugar primarily a component of the RNA used for genetic transcription, and as such is vitally important to all living creatures. It is not, however, an essential nutrient, since it can be made in the body from other substances, such as glucose.[5] It is a component of ATP, NADH, and several other chemicals that are critical to metabolism. It is primarily seen as D-ribose, and is an aldopentose.

Structures

Monosaccharides, such as ribose, are the simplest form of carbohydrates. They consist of one sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Other examples of monosaccharides include glucose, fructose, and galactose. Each carbon atom that supports a hydroxyl group (except for the first and last) is chiral, giving rise to a number of isomeric forms all with the same chemical formula. For instance, galactose and glucose are both aldohexoses, but they have different chemical and physical properties.[6]

With few exceptions monosaccharides (e.g. deoxyribose) have the basic chemical formula (CH2O)n and the chemical structure:

H(CHOH)nC=O(CHOH)mH

If n or m is zero, it is an aldehyde and is termed an aldose, otherwise it is a ketone and is termed a ketose. Monosaccharides contain either a ketone or aldehyde functional group, and hydroxyl groups on most or all of the non-carbonyl carbon atoms.[7]

Ribose is an aldopentose, which is a monosaccharide with five carbon atoms and an aldehyde functional group in position #1. The aldopentoses have three chiral centers, so 8 different stereoisomers are possible.[8]

The 4 D-aldopentoses are:

 CH=O        CH=O          CH=O         CH=O
 |           |             |            |
HC-OH     HO-CH           HC-OH      HO-CH
 |           |             |            |
HC-OH       HC-OH       HO-CH        HO-CH
 |           |             |            |
HC-OH       HC-OH         HC-OH        HC-OH
 |           |             |            |
 CH2OH       CH2OH         CH2OH        CH2OH
D-Ribose    D-Arabinose   D-Xylose    D-Lyxose[9]

The chair form of ribose follows a similar pattern as that for glucose with one exception. Since ribose has an aldehyde functional group, the ring closure occurs at carbon # 1, which is the same as glucose. The exception is that ribose is a pentose, five carbons. Therefore a five membered ring is formed. The -OH on carbon #4 is converted into the ether linkage to close the ring with carbon #1. This makes a 5 member ring - four carbons and one oxygen.

The aldehyde and ketone functional groups in these carbohydrates react with neighbouring hydroxyl functional groups to form intramolecular hemiacetals or hemiketals, respectively. The resulting ring structure is related to furan, and is termed a furanose. The ring spontaneously opens and closes, allowing rotation to occur about the bond between the carbonyl group and the neighbouring carbon atom — yielding two distinct configurations (α and β). This process is termed mutarotation.[10]

Synthesis

Steps in the ring closure (hemiacetal synthesis):

  1. . The electrons on the alcohol oxygen are used to bond the carbon #1 to make an ether.
  2. . The hydrogen is transferred to the carbonyl oxygen to make a new alcohol group.

Hemiacetal Functional Group: Carbon # 1 is now called the anomeric carbon and is the center of a hemiacetal functional group. A carbon that has both an ether oxygen and an alcohol group is a hemiacetal.[11]

Practical Uses

Example of Ribose Supplements

Today D-Ribose is used widely as a supplement for increasing muscular energy, boosting endurance, and promoting recovery. It efficiently improves energy levels for working out because it is very active in the synthesis of ATP. D-Ribose also helps recovering heart muscle tissue after coronary heart disease, heart attacks, heart surgery, or even organ transplants. There is a chance, however, that the heart may be damaged and permanently lose heart tissue.[12]

Related References

- plays a critical role in the production of ATP, which provides the energy for short burst of power movements during workout.

See Also