What are macromolecules? Give examples.

Macromolecules are large molecules composed of repeating subunits called monomers, which are covalently bonded together through polymerization reactions. These molecules are essential for various biological processes and structures in living organisms. There are four main classes of macromolecules found in biological systems:

1. Proteins: Proteins are macromolecules composed of amino acid monomers linked together by peptide bonds. They play diverse roles in cells, including enzymatic catalysis, structural support, transport of molecules, signaling, and immune defense. Examples of proteins include enzymes (e.g., amylase, catalase), structural proteins (e.g., collagen, actin), and antibodies.

2. Nucleic Acids: Nucleic acids are macromolecules that store and transmit genetic information. There are two types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA carries the genetic instructions necessary for the development, functioning, and reproduction of organisms, while RNA is involved in protein synthesis and regulation. Examples of nucleic acids include DNA, RNA, messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).

3. Carbohydrates: Carbohydrates are macromolecules composed of sugar monomers (monosaccharides) linked together by glycosidic bonds. They serve as a major source of energy for cells and play structural roles in organisms. Examples of carbohydrates include glucose, cellulose, starch, glycogen, and chitin.

4. Lipids: Lipids are a diverse group of macromolecules that are hydrophobic (insoluble in water). They include fats, oils, phospholipids, steroids, and waxes. Lipids serve as energy storage molecules, structural components of cell membranes, and signaling molecules. Examples of lipids include triglycerides, phospholipids (e.g., phosphatidylcholine), cholesterol, and hormones (e.g., testosterone, estrogen).

These macromolecules are essential for the structure, function, and regulation of biological systems, and they interact with each other to form complex cellular structures and pathways.