|
Types of biomolecules A diverse range of biomolecules exist, including: Nucleosides and nucleotides Nucleosides are molecules formed by attaching a nucleobase to a ribose ring. Examples of these include cytidine, uridine, adenosine, guanosine, thymidine and inosine. Nucleosides can be phosphorylated by specific kinases in the cell, producing nucleotides, which are the molecular building blocks of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Saccharides Monosaccharides are carbohydrates in the form of simple sugars. Disaccharides are formed from two monosaccharides joined together. Monosaccharides and disaccharides are sweet, water soluble, and crystalline. Examples of monosaccharides include the hexoses (glucose, fructose, and galactose) and pentoses (ribose, deoxyribose). Examples of disaccharides include sucrose, maltose, and lactose. Polysaccharides are polymerized monosaccharides, complex unsweet carbohydrates. They are, generally, large and often have a complex, branched, connectivity. They are insoluble in water and do not form crystals. Examples include starch, cellulose, and glycogen. Shorter polysaccharides, with 2-15 monomers, are sometimes known as oligosaccharides. Lipids Lipids are chiefly fatty acid esters, and are the basic building blocks of biological membranes. Another biological role is energy storage (e.g., triglycerides). Most lipids consist of a polar or hydrophilic head and one to three nonpolar or hydrophobic fatty acid tails, and therefore they are amphiphilic. Fatty acids consist of unbranched chains of carbon atoms that are connected by single bonds alone (saturated fatty acids) or by both single and double bonds (unsaturated fatty acids). The chains are usually 14-24 carbon groups long. For lipids present in biological membranes, the hydrophilic head is from one of three classes: Hormones Hormones are produced in the endocrine glands, where they are excreted into the bloodstream. They perform a wide range of roles in the various organs including the regulation of metabolic pathways and the regulation of membrane transport processes. Hormones may be grouped into three structural classes: Amino acids Amino acids are molecules that contain both amino and carboxylic acid functional groups. ( In biochemistry, the term amino acid is used when referring to those amino acids in which the amino and carboxylate functionalities are attached to the same carbon, plus proline which is not actually an amino acid). Amino acids are the building blocks of long polymer chains. With 2-10 amino acids such chains are called peptides, with 10-100 they are often called polypeptides, and longer chains are known as proteins. These protein structures have many structural and functional roles in organisms. There are twenty amino acids that are encoded by the standard genetic code, but there are more than 500 natural amino acids. When amino acids other than the set of twenty are observed in proteins, this is usually the result of modification after translation (protein synthesis). Only two amino acids other than the standard twenty are known to be incorporated into proteins during translation, in certain organisms: Besides those used in protein synthesis, other biologically important amino acids include carnitine (used in lipid transport within a cell), ornithine, GABA and taurine. Protein structure The particular series of amino acids that form a protein is known as that protein's primary structure. Proteins have several, well-classified, elements of local structure and these are termed secondary structure. The overall 3D structure of a protein is termed its tertiary structure. Proteins often aggregate into macromolecular structures, or quaternary structure. Metalloproteins A metalloprotein is a protein that contains a metal cofactor. The metal may be an isolated ion or may be coordinated with a nonprotein organic compound, such as the porphyrin group found in hemoproteins. In some cases, the metal is coordinated with both a side chain of the protein and an inorganic nonmetallic ion. This type of protein-metal-nonmetal structure is found in iron-sulfur clusters. Vitamins A vitamin is a compound that can not be synthesized(hi) by a given organism but is nonetheless vital to its survival or health. These compounds must be absorbed, or eaten, but typically only in trace quantities. See also | ||||||||||
|
| |||||||||||
 |
|
| |