核糖和核酮糖的区别

Key Difference – Ribose vs Ribulose

Carbohydratesare the mainmacronutrientspresent in the body. They are composed of carbon (C), hydrogen (H) and oxygen (O). Carbohydrates can bemonosaccharides, disaccharides, andpolysaccharides。The H:O ratio is 2:1. The most basic units of carbohydrates are monosaccharides. They are known as simple sugars. Since they are considered to be the simplest compounds, they cannot be further hydrolyzed. Monosaccharides give rise to various other compounds such as disaccharides and polysaccharides. Ribose and ribulose are considered as monosaccharides and arepentosesugars containing 5 carbon atoms.Ribose is more commonly known as aldopentose sugar due to the presence of analdehyde(-CHO) functional group. Ribulose contains aketone(-C=O) functional group and is referred to as a ketopentose sugar。这是the key difference between ribose and ribulose.

CONTENTS

1.Overview and Key Difference
2.What is Ribose
3.What is Ribulose
4.Similarities Between Ribose and Ribulose
5.Side by Side Comparison – Ribose vs Ribulose in Tabular Form
6.Summary

What is Ribose?

Ribose is a pentose sugar with the molecular formula C₅H₁₀O_5.It is more commonly known asaldopentose sugardue to the presence of an aldehyde functional group. The carbon atoms in the ribose structure are numbered from C1 to C5; this numbering starts from the carbon atom attached to the functional group OH.Deoxyriboseand ribose sugars are closely related. Their difference is mainly due to the OH group; OH group is attached to C2 in deoxyribose; hydrogen atom is connected to C2 in ribose.

Ribose is an important sugar that is involved in the synthesis ofnucleotides。The backbone of ribonucleic acid (RNA) is composed of ribose sugar which alternates with thephosphategroups. The formation of the backbone is completed once it binds to the nitrogenous bases. Ribose phosphates are considered to be the major components of nucleotidecoenzymes。Microorganisms utilize this in order to synthesize the amino acid histidine. Ribose is not only found in RNA; it is present as a major component ofATP(Adenosine triphosphate). ATP is considered as the energy currency of all cells. In humans, during strenuous exercise workouts, energy is depleted excessively. In order to enhance protein synthesis and regain the depleted energy requirements, ribose supplements are recommended.

What is Ribulose?

Ribulose, being a ketopentose, is a monosaccharide which contains five carbon atoms along with ketone functional group. There are two possibleenantiomersof ribulose. They are D-ribulose (D-erythro-pentulose) and L-ribulose (L-erythro-pentulose). Ribulose is synthesized through the pentose phosphate pathway and plays an important role in the formation of numerous bioactive substances. The pentose phosphate pathway is a metabolic pathway which is parallel toglycolysis, and it consists of two distinct pathways. Here,NADPHis generated in the oxidative phase whereas pentose is generated through the non- oxidative phase. D-ribulose is considered as an example as it is an intermediate in the fungal pathway which helps in the production of D-arabitol.

Furthermore, D-ribulose and 1,5-bisphosphate combines with carbon dioxide initially in thephotosynthesisprocess in green plants. Ribulose 1,5-bisphosphate (RuBP) is a colourless anion and a double phosphate ester of the ketopentose; Ribulose. Ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO) carries out the catalysis of the reaction between RuBP and carbon dioxide during photosynthesis. This is the initial step of carbon fixation; thus, carbon dioxide is converted to energy-rich molecules such as glucose. In theCalvin cycle, RuBP is produced through the phosphorylation of ribulose-5-phosphate by ATP.

What are the Similarities Between Ribose and Ribulose?

• Both ribose and ribulose are monosaccharides.
• They are pentose sugars containing 5 carbons.
• They share a common chemical formula, C₅H₁₀O₅
• Both are structural isomers.

What is the Difference Between Ribose and Ribulose?

Ribose vs Ribulose
Ribose is an aldose sugar-containing an aldehyde group (-CHO).	Ribulose contains a ketone group (-C=O) and is referred to as a ketose sugar.
Double Bond
In ribose, the first carbon consists of a double bond.	In ribulose, the double bond is on the second carbon.
Function
The backbone of ribonucleic acid (RNA) is formed by ribose.	In the Calvin cycle (dark reaction) of photosynthesis, ribulose bisphosphate is the initial CO2 acceptor.

Summary – Ribose vs Ribulose

Carbohydrates are the major macronutrients present in the body. Monosaccharides are simple sugars that have the ability to synthesize different compounds such as disaccharides and polysaccharides. Ribose and Ribulose are two monosaccharides. Both are pentose sugars. Ribose consists of an aldehyde functional group and is commonly referred to as aldopentose sugar. Ribulose is known as ketopentose sugar due to the presence of a ketone functional group. This is the difference between Ribose and Ribulose. Due to these structural differences, ribose and ribulose have varied functions in the living system.

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References:

1. Reid, Danielle. “Aldose vs. Ketose Sugars.” Study.com.Available here。Accessed 18 Aug. 2017.
2. Arrington, Derrick. “What is Ribose? – Structure, Overview.” Study.com.Available here.Accessed 18 Aug. 2017.

Image Courtesy:

1. “ribose(uda3)” by chronoxphya(CC BY 2.0)viaFlickr
2. “DL-Ribulose” By NEUROtiker – Own work (Public Domain) viaCommons Wikimedia