Describe how a monomer is the basic unit of all macromolecules.
A monomer is the basic unit of all macromolecules, including proteins, carbohydrates, lipids, and nucleic acids. To understand why a monomer is considered the building block of macromolecules, let's dive into each type of macromolecule.
1. Proteins: The monomers of proteins are amino acids. There are 20 different amino acids that can be combined in various sequences to form a wide range of proteins. During protein synthesis, amino acids are joined together through peptide bonds, forming a chain called a polypeptide.
2. Carbohydrates: The monomers of carbohydrates are monosaccharides, such as glucose, fructose, and galactose. Monosaccharides can combine through glycosidic bonds to form larger carbohydrates including disaccharides (e.g., sucrose) and polysaccharides (e.g., starch, cellulose).
3. Lipids: Unlike proteins and carbohydrates, lipids do not have a specific monomer. However, they are composed of fatty acids and glycerol. Fatty acids are long chains of hydrocarbons with a carboxyl group at one end, while glycerol is a three-carbon molecule. Through a process called esterification, fatty acids can bond with glycerol to form triglycerides, the most common type of lipid.
4. Nucleic acids: Nucleotides are the monomers of nucleic acids, which include DNA and RNA. Nucleotides consist of a sugar molecule (deoxyribose in DNA and ribose in RNA), a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or thymine/uracil). These nucleotides connect through phosphodiester bonds, forming long chains.
In summary, monomers are the fundamental units that make up macromolecules. Through chemical reactions such as condensation or dehydration synthesis, monomers are linked together to form polymers, which are large, complex macromolecules. Understanding the composition and structure of monomers helps elucidate the diverse functions and properties of macromolecules in living organisms.