Definition: Adenosine, also known as 5-deoxy-3-phosphoglycerate, is a chemical compound that plays an essential role in the energy metabolism of cells. It's a naturally occurring sugar that is synthesized from the amino acid adenosine mononucleotide (AMP) through a process called phosphorylation. Adenosine can be found in the nucleus and cytoplasm of cells as a coenzymes with the enzyme deaminase, which is involved in the synthesis of ATP. The chemical structure of adenosine involves two phosphorus atoms bonded to four nitrogen atoms, forming a pentagonal boron octahedron. Adenosine has several important functions in the body: 1. Regulating cell membrane permeability: Adenosine acts as an excitatory neurotransmitter and is involved in regulating cell membrane fluidity, which plays a key role in many cellular processes. 2. Signal transduction: Adenosine has also been shown to play a significant role in signal transduction pathways, where it modulates the activity of signaling molecules such as cAMP, IP3, and DAG. 3. Regulation of gene expression: Adenosine can be found in various parts of the cell, including the nucleus and cytoplasm, which allows it to influence gene expression by binding to regulatory regions within genes and modulating their expression levels. 4. Synthesis of DNA: Some forms of adenosine (adenosylated) are involved in DNA synthesis, as they can interact with DNA polymerase II during transcription. 5. Regulation of cell proliferation: Adenosine has been shown to regulate the progression of cell division by inducing nuclear factor kappa-light-chain-enhancer of activated genes and inhibiting the activity of the cyclin-dependent kinase 1 (CDK1) inhibitor CDK2. Adenosine plays a crucial role in maintaining cellular homeostasis, regulating gene expression, signaling pathways, and many other physiological processes.

adenoses