Amino Acid vs Nucleotide
Amino acids and nucleotides are building blocks of two important macromolecules in biological systems. Both are organic molecules and present in high concentrations inside cells.
Amino acid is a simple molecule formed with C, H, O, N and may be S. It has the following general structure.
There are about twenty common amino acids. All the amino acids have a –COOH, -NH2 groups and a –H bonded to a carbon. The carbon is a chiral carbon, and alpha amino acids are the most important in the biological world. D-amino acids are not found in proteins and not a part of metabolism of higher organisms. However, several are important in the structure and metabolism of lower forms of life. The R group differs from amino acid to amino acid. The simplest amino acid with the R group being H is glycine. According to the R group, amino acids can be categorized into aliphatic, aromatic, non polar, polar, positively charged, negatively charged, or polar uncharged, etc. Amino acids present as zwitter ions in the physiological pH 7.4. Amino acids are the building blocks of proteins. When two amino acids join to form a dipeptide, the combination takes place in a -NH2 group of one amino acid with the –COOH group of another amino acid. A water molecule is removed, and the formed bond is known as a peptide bond. Thousands of amino acids can be condensed like these to form long peptides, which are then folded into make proteins.
Nucleotide is the building block of two crucial macromolecules (nucleic acids) in living organisms called DNA and RNA. They are the genetic material of an organism and are responsible for passing genetic characteristics from generation to generation. Further, they are important to control and maintain cellular functions. Other than these two macromolecules, there are other important nucleotides. For example, ATP (Adenosine tri phosphate) and GTP are important for energy storage. NADP and FAD are nucleotides, which act as cofactors. Nucleotides like CAM (cyclic adenosine monophosphate) are essential for cell signaling pathways.
A nucleotide is composed of three units. There is a pentose sugar molecule, a nitrogenous base and the phosphate group/s. According to the type of pentose sugar molecule, nitrogenous base and the number of phosphate groups, nucleotides differ. For example, in DNA, there is a deoxyribose sugar and in RNA, there is a ribose sugar. There are mainly two groups of nitrogenous bases as pyridines and pyrimidines. Pyrimidines are smaller heterocyclic, aromatic, and six-member rings containing nitrogens at 1 and 3 positions. Cytosine, thymine, and uracil are examples for pyrimidine bases. Purine bases are much larger than pyrimidines. Other than the heterocyclic aromatic ring, they have an imidazole ring fused to that. Adenine and guanine are the two purine bases. In DNA and RNA, complimentary bases form hydrogen bonds between them. That is adenine: thiamine/ uracil and guanine: cytocine are complimentary to each other. The phosphates are linked to the –OH group of carbon 5 of the sugar. In the nucleotides of DNA and RNA, normally there is a one phosphate group.
What is the difference between Amino Acid and Nucleotide?
• Amino acids are building blocks of protein and nucleotides are building blocks of nucleic acids.
• Amino acids have C, H, O, N, S. Nucleotides have C, H, O, N, P
• Amino acids are simple molecules whereas nucleotides are complex than that with a combination of 3 groups.
• Amino acids are important in protein synthesis, whereas nucleotides in cells have a variety of functions other than making DNA and RNA.