Nucleic Acids: Building Blocks of Life

Study Notes

Nucleic acids, like DNA and RNA, are essential molecules found in all living organisms.
These molecules store and transmit genetic information, which is the blueprint for life.
Nucleic acids are composed of monomers called nucleotides.

A nucleotide consists of three components: a five-carbon sugar (pentose), a phosphate group, and a nitrogenous base.
There are two types of nitrogenous bases: purines (adenine and guanine) and pyrimidines (cytosine, thymine, and uracil).
Purines have a double-ring structure, while pyrimidines have a single-ring structure.
The sugar in DNA is deoxyribose, while the sugar in RNA is ribose.

Nucleotides are linked together by phosphodiester bonds, forming a sugar-phosphate backbone.
The sugar-phosphate backbone gives DNA its negative charge.
The nitrogenous bases project inwards from the backbone, forming base pairs.
DNA is a double helix, with two antiparallel strands held together by hydrogen bonds between the complementary base pairs: adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C).
RNA is typically single-stranded and can fold into complex structures, with the base pairings: A with U (uracil), G with C.

Number of Strands: DNA is double-stranded, while RNA is usually single-stranded.
Sugar: DNA contains deoxyribose, while RNA contains ribose.
Bases: DNA contains thymine, while RNA contains uracil.

DNA stores genetic information, which is passed on from generation to generation.
DNA is transcribed into RNA, which is used to synthesize proteins.
RNA plays a role in protein synthesis – mRNA (messenger RNA) carries genetic information from DNA, tRNA (transfer RNA) brings amino acids to the ribosome, and rRNA (ribosomal RNA) is a component of ribosomes.
Nucleotides are involved in metabolic activities, regulate enzymatic reactions, and store energy (ATP).

Nucleic acids are broken down (catabolized) into their component nucleotides.
Degradation starts with digestion in the small intestine, followed by enzymatic breakdown of oligonucleotides (short nucleotide chains) into individual nucleotides.
Nucleotides are further hydrolyzed to nucleosides, and then to bases and sugars.
Salvage pathways are important for recycling the breakdown products of nucleic acid degradation to synthesize new nucleotides.
An alternative salvage pathway helps regenerate ribose-5-phosphate, a key intermediate in purine and pyrimidine biosynthesis.

Purines and pyrimidines are synthesized from simpler precursors via complex metabolic pathways.
The synthesis of purines and pyrimidines is tightly regulated to ensure proper balance in the cell.