Nucleotides and phosphodiester bonds

What is a nucleotide and what are its three components? ( draw diagram of structure too)

A nucleotide is the monomer of DNA and RNA.
It consists of:

• Pentose sugar (ribose or deoxyribose)

• Nitrogen-containing base

• Phosphate group

Nucleotides join to form polynucleotides (DNA/RNA).

What are the components of DNA and RNA nucleotides?

DNA nucleotide:

• Pentose: Deoxyribose

• Bases: A, C, G, T

• Phosphate group

RNA nucleotide:

• Pentose: Ribose

• Bases: A, C, G, U

• Phosphate group

• DNA contains thymine; RNA contains uracil

• DNA has deoxyribose; RNA has ribose

Which bases are purines and which are pyrimidines? What is the difference?

Purines (double-ring):

• Adenine (A)

• Guanine (G)

Pyrimidines (single-ring):

• Cytosine (C)

• Thymine (T)

• Uracil (U)

What is the structural difference between ribose and deoxyribose?

Both are pentose sugars.

• Ribose has –OH on carbon 2

• Deoxyribose has –H on carbon 2

Therefore, deoxyribose has one fewer oxygen atom.

How are nucleotides joined to form DNA/RNA?

• Nucleotides join in a condensation reaction

• Between phosphate of one nucleotide and carbon 3 of the next sugar

• Forms a phosphodiester bond (phosphate + two ester bonds)

• Repeated bonding forms the sugar-phosphate backbone

How are DNA or RNA chains broken down?

• The reverse of condensation

• Hydrolysis reactions

• Break phosphodiester bonds

• Releases individual nucleotides

List three structural differences between DNA and RNA.

• Sugar: DNA has deoxyribose; RNA has ribose.

• Bases: DNA uses thymine; RNA uses uracil.

• Strands: DNA is double-stranded (double helix); RNA is single-stranded.