We know that all matter is made up of atoms and molecules. Atoms are the smallest units of matter, and molecules are composed of two or more atoms. But imagine a molecule that is composed of thousands or more atoms. It would look like a very long necklace, with thousands of pearls, where each pearl is an atom and the necklace is the molecule. Those molecules are called Macromolecules, meaning big (macro) molecules. In this lesson, we will:
Macromolecules are large, complex molecules, composed of thousands of atoms. Or we can say that macromolecules are formed by many monomers linking together, forming a polymer. A monomer is a molecule of any of a class of compounds (mostly organic), that can react with other molecules to form very large molecules. Those large molecules are called polymers. That is why macromolecules are also called polymers.
The food we eat, the objects around us, nature, even we, are all constructed of macromolecules. All the macromolecules are divided into four major classes of biological macromolecules:
Like all other macromolecules, carbohydrates are built from smaller organic molecules and are necessary for life. Their name comes from the composition. Because they are made up of carbon and water (hydro), they are called carbohydrates. Living organisms use carbohydrates as accessible energy to fuel cellular reactions and for structural support inside cell walls. That is why carbohydrates are a very important part of our diet. Fruits, and vegetables, grains are natural sources of carbohydrates. They provide our bodies with energy, particularly through glucose. Glucose is a simple sugar that is a component of starch and an ingredient in many basic foods. Carbohydrates can be divided into groups according to the number of individual simple sugar units. Monosaccharides contain a single sugar unit; disaccharides contain two sugar units; and polysaccharides contain many sugar units as in polymers - most contain glucose as the monosaccharide unit.
Lipids are a diverse group of hydrophobic (“water-fearing”), or insoluble in water bio-molecules. But, lipids are smaller than the other three types of macromolecules, and the main difference with them is that the lipids do not form polymers. So, we will conclude that lipids are not polymers, because they are not built from monomers. They are long chains of carbon and hydrogen molecules and are classified as simple and complex. Major types include fats and oils, waxes, phospholipids, and steroids. Lipids perform different functions in cells. They are responsible for storing energy, signaling, and they are acting as structural components of cell membranes. The most common form of lipid found in food is triglycerides. Triglycerides contain a glycerol molecule and 3 fatty acids.
Proteins are macromolecules, consisting of one or more long chains of amino acid residues. There are 20 different types of amino acids that can be combined to make a protein. Proteins play many critical roles in the body. They do most of the work in cells. Also, the proteins are required for the function, structure, and regulation of the body’s organs and tissues. Protein is an important building block of bones, muscles, cartilage, skin, and blood. Hair and nails are mostly made of protein. Protein provides the body with approximately 10 to 15% of its dietary energy. It is the second most abundant compound in the body, following water. We can easily meet our protein needs by eating a variety of foods. High protein foods include meat, cheese, milk, beans, lentils, nuts, eggs, etc.
Nucleic acids are the biological macromolecules essential to all known forms of life. The term nucleic acid is the overall name for DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid). They are composed of nucleotides. A nucleotide is made up of three components: a nitrogenous base, a pentose sugar, and a phosphate group. The functions of nucleic acids have to do with the storage and expression of genetic information, they code the genetic information of organisms. Nucleic acids are part of our diet too. Milk and eggs are a logical source of nucleic acids, but plants too are a source of food that contains nucleic acids.
