# Ribose & Deoxyribose --- **Ribose** and **deoxyribose** are two pentose [[monosaccharide|monosaccharides]] that differ by one functional group. Ribose has a [[hydroxyl]] on it's 2' sugar and deoxyribose does not. They are essential components in [[nucleotide|nucleotides]]. ![[ribose and deoxyribose.png]] ## Structure ### The Oxygen The very top of the pentagram is a single **oxygen**. Note, that while these are both 5 carbon sugars, and there are 5 points in the pentose shape, the 5th carbon is actually bonded to the 4' carbon and not part of the pentagram shape—this oxygen is. ### 1' Carbon & The Nitrogenous Base The **1' carbon** (going counter clockwise as per convention) in the sugar is the one that binds to the [[nucleotide#Nitrogenous Bases|nitrogenous base]]. ### 2' Carbon & The Distinction The **2' carbon** is where we find the distinction between ribose and deoxyribose. The 2' carbon on the ribose has a [[hydroxyl|hydroxyl]] group attached, while a deoxyribose does not (hence "deoxy-"). ### 3' Carbon & The [[Hydroxyl]] The **3' carbon** is important for [[DNA replication]], because this is where the next nucleotide is attached to via a [[DNA structure|phosphodiester linkage]]. Remember: Nucleic acid synthesis moves from the 5' to the 3' direction because elongating from the 3' end has to wait for a triphophate group to float by so it can use the stored energy. ### 4' Carbon The **4' carbon** is also there. ### 5' Carbon & The Phosphate Group The **5' carbon** is also important for [[DNA replication]], because this is where the **triphosphate group is attached** naturally. When it comes time to link up, there is already a phosphate group there, if this is a nucleotide already attached to the strand, it's attached by the phosphate, so it receives a new phosphate on it's 3'. If it's a free floating nucleotide, the triphophate (attached to the 5') is where the energy is used to plug it into the strand. ![[phosphodiester bond.png]] ___