Nucleotides and Nucleic Acids Overview

Study Notes

Nucleotides: Building Blocks of Nucleic Acids

Nucleotides are the building blocks of DNA and RNA.
They are not essential nutrients, as the body can synthesize them.
They are crucial components of ATP, the cell's primary energy source.
Nucleotides are also part of coenzymes like NAD, NADP, and FAD.
They form cAMP and cGMP, acting as secondary messengers for hormones.
Nucleotides regulate metabolic pathways by inhibiting or activating enzymes.
Purine and pyrimidine bases in nucleotides can be synthesized de novo or through salvage pathways.
Nucleic acids are linear polymers, storing and transmitting genetic information for growth and reproduction.
Purines include adenine and guanine; pyrimidines include cytosine, uracil, and thymine.
Thymine and uracil differ; only thymine has a methyl group.
Some organisms have unusual DNA/RNA bases (modified bases), e.g., in some viruses and tRNA. Modifications include methylation, acetylation, reduction, and glycosylation.

Nucleosides

A nucleoside forms when a pentose sugar (ribose or deoxyribose) links to a purine or pyrimidine base via an N-glycosidic bond.
Ribose forms ribonucleosides; deoxyribose forms deoxyribonucleosides.
Examples: Adenine forms deoxyadenosine, guanine forms deoxyguanosine, cytosine forms deoxycytidine, thymine forms deoxythymidine, uracil forms uridine, adenine in RNA forms adenosine, etc.
A table would show the relationship.

Nucleotides: Building Blocks

Nucleotides are formed when one or more phosphate groups attach to a nucleoside.
Each nucleotide has a base (purine or pyrimidine), a pentose sugar (ribose or deoxyribose), and phosphate groups.
Phosphate groups attach to the 5' carbon of the pentose sugar via ester linkages.
The phosphate groups impart a significant negative charge to DNA and RNA.

Nucleotide Synthesis Pathways

Three pathways synthesize nucleotides:
- De novo synthesis: Synthesizes nucleotides from metabolic precursors (amino acids, ribose-5-phosphate, CO2, one-carbon units). These enzymes are found in liver, small intestine, and thymus.
- Salvage pathways: Recycles free bases or nucleosides from broken-down RNA and DNA, to recover bases/nucleosides.
- Conversion of ribonucleotides to deoxyribonucleotides: Occurs at the level of nucleoside diphosphates, converting ADP, CDP, GDP, and UDP. Ribonucleotide reductase (RR) enzyme is responsible.

Naming Nucleotides

adding a phosphate to a pentose= Monophosphates (e.g., AMP, adenylate).
adding a second or third phosphate=Diphosphates (e.g., ADP) or Triphosphates (e.g., ATP).

Description

This quiz explores the fundamental role of nucleotides as the building blocks of nucleic acids such as DNA and RNA. It covers their synthesis, functions in energy transfer, and regulatory roles in metabolic pathways. Additionally, the quiz delves into the differences between purine and pyrimidine bases and their unique characteristics.