Macromolecules are the large molecules necessary for life that are built from smaller subunits. There are four major classes of biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids), and each is an important component of the cell and performs a wide array of functions. Biological macromolecules are organic, meaning they contain carbon and are bound to hydrogen.
Most macromolecules are made from single subunits, or building blocks, called monomers.
Dehydration Synthesis: The process in which monomers combine with each other to form larger molecules known as polymers. In doing so, monomers release water molecules as byproducts. Dehydration synthesis means “to put together while losing water.”
Hydrolysis: The process in which polymers break down into monomers. A chemical reaction occurs when inserting a water molecule across the bond, hence the term hydrolysis: hydro (water) lysis (to break).
Monomer = monosaccharide
Carbohydrates provide energy to the body, particularly through glucose, a simple sugar.
Carbohydrates can be represented by the formula (CH2O)n, where n is the number of carbon atoms in the molecule. In other words, the ratio of carbon to hydrogen to oxygen is 1:2:1 in carbohydrate molecules. Carbohydrates are classified into three subtypes: monosaccharides, disaccharides, and polysaccharides.
- Monosaccharides: (mono- = “one”; sacchar- = “sweet”) These
are simple sugars, the most common of which is glucose. In
most living species, glucose is an important source of energy.
During cellular respiration, energy is released from glucose,
and that energy is used to help make adenosine triphosphate
(ATP).
- Disaccharides: (di- = “two”) These form when two
monosaccharides undergo a dehydration reaction. A common
disaccharide is lactose, naturally found in milk. Lactose is a
disaccharide consisting of the monomers glucose and
galactose.
- Polysaccharide: (poly- = “many”) These are a long chain of
monosaccharides linked by covalent bonds. Glycogen is the
storage form of glucose in humans and bacteria, and is made
up of monomers of glucose. In humans it is usually stored in liver
and muscle cells. Whenever glucose levels decrease, glycogen
is broken down to release glucose.
Monomer = Fatty acid + glycerol
Lipids include a diverse group of compounds that are united by a common feature, they are hydrophobic (“water-fearing”), or insoluble in water.
Cells store energy for long-term use in the form of lipids called fats. Lipids also provide insulation from the environment. Lipids are also the building blocks of many hormones and are an important constituent of the plasma membrane - phospholipids.
Monomer = amino acids
The functions of proteins are very diverse because there are 20 different chemically distinct amino acids that form long chains, and the amino acids can be in any order. For example, proteins can function as enzymes, hormones, transport proteins in the cell membrane or structural proteins (like the protein subunits that make up the flagella which is used for cell movement).
Protein shape is critical to its function. Changes in temperature, pH, and exposure to chemicals may lead to permanent changes in the shape of the protein, leading to a loss of function or denaturation.
Monomer = Nucleic acid
Nucleic acids carry the genetic blueprint of a cell and carry instructions for the functioning of the cell.
The two main types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is the genetic material found in all living organisms, ranging from single-celled bacteria to multicellular mammals. The other type of nucleic acid, RNA, is mostly involved in protein synthesis.
