Nucleic Acids and Nucleotides Overview

Nucleic Acids (DNA and RNA)

• DNA stores genetic information, permanently located in the cell nucleus.
• RNA is temporary, found in the cytoplasm, and its presence depends on cellular needs. mRNA is a type of RNA that carries instructions, while other RNA types have functional roles.
• Nucleic acids are polymers constructed from nucleotide monomers.
• DNA and RNA are examples of nucleotide polymers.

Nucleotides Occurrence in the Cell

• Nucleotides are the monomers of nucleic acids.
• Important energetic compounds include ATP, ADP, AMP, GTP, GDP, GMP, CTP, CDP, CMP, TTP, TDP, TMP.
• These energetic compounds are crucial for cellular processes.
• DNA and RNA are polymers made up of nucleotides.

Nucleotide & Nucleoside

• Nucleotides are composed of a sugar, a nitrogenous base, and a phosphate group.
• Nucleosides consist of a sugar and a nitrogenous base.
• RNA contains oxyribose sugar; DNA contains deoxyribose sugar.

Nucleoside Composition

• Nucleosides are composed of a pentose sugar and a nitrogenous base, without a phosphate group.
• Ribonucleoside (R=OH) and 2'-Deoxyribonucleoside (R=H) are examples of nucleosides.

Nucleotide Composition

• Nucleotides consist of a pentose sugar, a nitrogenous base, and a phosphate group.
• Nitrogenous bases include A, T, C, G.
• The phosphate group is attached to the sugar.

Pentose Sugars in RNA and DNA

• RNA contains ribose sugar.
• DNA contains deoxyribose sugar.
• The carbon atoms in the sugar are numbered with primes (') to differentiate them from the nitrogenous bases.

Types of Nucleic Acids

• RNA (Ribonucleic acid)
• DNA (Deoxyribonucleic acid)
• Both are polymers of nucleotides linked by phosphodiester bonds.

Chemical Structure of Nucleic Acids - Monomers

• Nucleotides are the monomers.
• Pyrimidines link to the pentose sugar via C1' to C1'.
• Purines link to the pentose sugar via N9 to C1'.
• Examples include deoxyadenosine 5'-triphosphate (dATP) and cytidine 5'-monophosphate (CMP).

Nitrogen Bases

• Purines have two carbon-nitrogen rings (C1'-N9).
• Examples include adenine (A) and guanine (G).
• Pyrimidines have one carbon-nitrogen ring (C1'-N1).
• Examples include cytosine (C), thymine (T), and uracil (U).

Nomenclature of Nucleotide

• Nucleotides are named based on their nitrogenous base.
• Adenine is denoted as dATP (deoxyadenosine triphosphate), guanine is dGTP (deoxyguanosine triphosphate), and so on.

Types of Bonds in DNA

• Glucosidic bonds connect the sugar and nitrogenous base.
• Phosphodiester bonds link successive nucleotides.
• Hydrogen bonds form between complementary base pairs (C-G, A-T).

Formation of the 3' to 5' Phosphodiester Bond

• Covalent bonds form between the phosphate group and two 5-carbon ring carbohydrates (pentoses) across two ester bonds. This is a strong covalent bond.
• The phosphodiester bond forms the linkage between the 3' carbon atom of one sugar and the 5' carbon of another.

DNA Helix

• DNA is a large molecule made of nucleotides.
• Nucleotides consist of a deoxyribose sugar, a phosphate group, and a nitrogenous base.

The Most Common Organic Bases

• The most common organic bases in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G).

Bonding

• Adenine (A) pairs with Thymine (T) via two hydrogen bonds.
• Cytosine (C) pairs with Guanine (G) via three hydrogen bonds.

DNA Properties – Model of Watson and Crick (1953)

• DNA has a 3-dimensional structure.
• DNA has two antiparallel polynucleotide chains.
• The chains run in opposite directions (5' to 3' and 3' to 5').
• The structure has a sugar-phosphate backbone on the outside and nitrogenous bases on the inside.
• The strands are held together by hydrogen bonds between the bases.
• Each turn of the helix has about 10 base pairs.
• The helix has a diameter of 2 nanometers.
• The helix has major and minor grooves.