how many hydrogen bonds form between g and c
GC-content The GC pair is bound by three hydrogen bonds, while AT and AU pairs are bound by two hydrogen bonds. To emphasize this difference in the number of hydrogen bonds, the base pairings can be represented as respectively Gâ‰¡C versus A=T and A=U. DNA with low GC-content is less stable than DNA with high GC-content; however, the hydrogen bonds themselves do not have a particularly significant impact on stabilization, the stabilization is due mainly to interactions of base stacking.[2] In spite of the higher thermostability conferred to the genetic material, it has been observed that at least some bacteria species with DNA of high GC-content undergo autolysis more readily, thereby reducing the longevity of the cell per se.[3] Due to the thermostability given to the genetic materials in high GC organisms, it was commonly believed that the GC content played a necessary role in adaptation temperatures, a hypothesis that was refuted in 2001.[4] However, it has been shown that there is a strong correlation between the prokaryotic optimal growth at higher temperatures and the GC content of structured RNAs (such as ribosomal RNA, transfer RNA, and many other non-coding RNAs).[4][5] The AU base pairs are less stable than the GC base pairs previously attributed to GC bonds containing 3 hydrogen bonds and AU having only 2 hydrogen bonds, making high-GC-content RNA structures more resistant to the effects of high temperatures. More recently, it has been proved that the most stabilizing factor of thermal stability of double stranded nucleic acids is actually due to the base stackings of adjacent bases, rather than the number of hydrogen bonds between the bases.There is more favorable stacking energy for G:C pairs because of the relative positions of exocyclic groups than in the A:U pairs. Additionally, there is a correlation between the order in which the bases stack and thermal stability.[6]
Monosaccharide Monosaccharides (from Greek monos: single, sacchar: sugar), also called simple sugars, are the most basic units of carbohydrates.[1] They are fundamental units of carbohydrates and cannot be further hydrolyzed to simpler compounds. The general formula is C nH 2nO n. They are the simplest form of sugar and are usually colorless, water-soluble, and crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose (dextrose), fructose (levulose) and galactose. Monosaccharides are the building blocks of disaccharides (such as sucrose and lactose) and polysaccharides (such as cellulose and starch). Further, each carbon atom that supports a hydroxyl group (so, all of the carbons except for the primary and terminal carbon) 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 have different physical structures and chemical properties.