2.26 RNA structure

What is RNA?

• RNA = ribonucleic acid.

• RNA is a polynucleotide made up of many nucleotides joined together.

• It is usually single-stranded.

• RNA molecules are generally shorter than DNA molecules.

Ribose sugar

• RNA contains ribose sugar.

• Ribose has a hydroxyl (OH) group attached to its 2′ carbon.

• DNA contains deoxyribose, which has hydrogen (H) instead of OH at the 2′ carbon.

Why does RNA have a shorter molecular lifespan?

• The 2′ hydroxyl group makes RNA more susceptible to hydrolysis.

• This makes RNA less chemically stable than DNA.

Sugar phosphate backbone

• RNA nucleotides are joined together by phosphodiester bonds.

• These are strong covalent bonds.

• They form through condensation reactions.

• The phosphate group links the 3′ carbon of one ribose sugar to the 5′ carbon of the next.

• This creates an alternating sugar-phosphate backbone.

• Nitrogenous bases project out from the backbone.