A pentose is a monosaccharide with five carbon atoms. Monosaccharides (from Greek monos: single sacchar: sugar are the most basic unit of Carbohydrates They consist of one sugar and Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny
They either have an aldehyde functional group in position 1 (aldopentoses), or a ketone functional group in position 2 (ketopentoses). An aldehyde is an organic compound containing a terminal Carbonyl group. In Organic chemistry, functional groups are specific groups of Atoms within Molecules that are responsible for the characteristic Chemical reactions A ketone (pronounced as key tone) is either the Functional group characterized by a Carbonyl group (O=C linked to two other Carbon atoms or
The aldopentoses have three chiral centres ("asymmetric carbon atoms") and so 8 different stereoisomers are possible. Stereoisomers are isomeric molecules that have the same molecular formula and sequence of bonded atoms (constitution but which differ in the three dimensional orientations
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
A mnemonic suggested that can be used to remember the four D-aldopentoses is "ribs are extra lean. Ribose (ɹˈaɪbəʊs ɹˈaɪbəɹʊs primarily seen as D-ribose, is an Aldopentose — a Monosaccharide containing five Carbon Arabinose is an Aldopentose &mdash a Monosaccharide containing five Carbon Atoms and including an Aldehyde (CHO Functional Xylose or wood sugar is an Aldopentose &mdash a Monosaccharide containing five Carbon Atoms and including an Aldehyde Functional Lyxose is an Aldopentose &mdash a Monosaccharide containing five Carbon Atoms and including an Aldehyde Functional group A mnemonic device (nəˈmɒnɪk is a Memory aid Commonly met mnemonics are often verbal something such as a very short poem or a special word used to help a person remember "
The ketopentoses have 2 chiral centres and therefore 4 possible stereoisomers — ribulose (L- and D-form) and xylulose (L- and D-form). Ribulose is a Ketopentose &mdash a Monosaccharide containing five Carbon Atoms and including a Ketone Functional group Xylulose is a Ketopentose, a Monosaccharide containing five Carbon Atoms and including a Ketone Functional group.
The D-isomers of both are known to occur naturally as is the L-isomer of xylulose:
CH2OH CH2OH | | C=O C=O | | HC-OH HO-CH | | HC-OH HC-OH | | CH2OH CH2OH D-Ribulose D-Xylulose
The aldehyde and ketone functional groups in these carbohydrates react with neighbouring hydroxyl functional groups to form intramolecular hemiacetals or hemiketals, respectively. Xylulose is a Ketopentose, a Monosaccharide containing five Carbon Atoms and including a Ketone Functional group. Ribulose is a Ketopentose &mdash a Monosaccharide containing five Carbon Atoms and including a Ketone Functional group Xylulose is a Ketopentose, a Monosaccharide containing five Carbon Atoms and including a Ketone Functional group. Hydroxyl in Chemistry stands for a molecule consisting of an Oxygen atom and a Hydrogen atom connected by a Covalent bond. Intramolecular in Chemistry describes a process or characteristic limited within the structure of a single Molecule; a property or phenomenon limited to the extent Hemiacetals and hemiketals are compounds of the general formula R1R2C(OHOR3 where R3 is not a hydrogen Hemiacetals and hemiketals are compounds of the general formula R1R2C(OHOR3 where R3 is not a hydrogen The resulting ring structure is related to furan, and is termed a furanose. Furan, also known as furane and furfuran, is a heterocyclic Organic compound. A furanose is a simple Sugar that contains a five-membered Furan -based ring structure and is a sub-terminal ketone which gives it reducing power 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. Mutarotation is the term given to the change in the Specific rotation of a cyclic Monosaccharide as it reaches an equilibrium between its &alpha and &beta Anomeric
Ribose is a constituent of RNA, and the related deoxyribose of DNA. Ribose (ɹˈaɪbəʊs ɹˈaɪbəɹʊs primarily seen as D-ribose, is an Aldopentose — a Monosaccharide containing five Carbon Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units Deoxyribose, also known as D-Deoxyribose and 2-deoxyribose, is an Aldopentose &mdash a Monosaccharide containing five Carbon Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known
See also
A triose is a Monosaccharide containing three Carbon Atoms There are only two trioses an aldotriose ( Glyceraldehyde) and a A tetrose is a Monosaccharide with 4 Carbon atoms They either have an Aldehyde Functional group in position 1 ( aldotetroses) In Organic chemistry, a hexose is a Monosaccharide with six Carbon atoms having the Chemical formula C6H12O6 A heptose is a Monosaccharide with seven Carbon atoms They either have an Aldehyde Functional group in position 1 ( aldoheptoses The pentose phosphate pathway (also called Phosphogluconate Pathway or HexoseMonophosphate Shunt shunt is a process that serves to generate NADPH and the synthesis of pentoseDapyx Software network: MP3 Explorer | Ebook Manager | Zenithic