Proteins are large, complex molecules found in all living organisms, serving as one of the fundamental macromolecules alongside carbohydrates, lipids, and nucleic acids. Often referred to as the “building blocks” of life, these intricate structures are formed from smaller units called amino acids linked together in long chains. Their diverse shapes and compositions allow them to perform an astonishing array of tasks, underpinning nearly every biological process within the body.
What Proteins Do in the Body
Proteins perform a vast array of tasks indispensable for life. Many proteins provide structural support, forming the framework of tissues and organs. Examples include collagen, which gives strength to connective tissues like bone, cartilage, and skin, and keratin, which forms hair and nails.
Other proteins function as enzymes, acting as biological catalysts to speed up chemical reactions within cells without being consumed in the process. Digestive enzymes like amylase and pepsin, for instance, break down complex food molecules into simpler forms that the body can absorb. Proteins also play a significant role in transport, moving molecules throughout the body. Hemoglobin, found in red blood cells, is a well-known example, responsible for carrying oxygen from the lungs to various tissues.
Proteins are integral to the body’s immune defense system. Antibodies, specialized proteins, recognize and neutralize foreign invaders like bacteria and viruses, protecting the body from illness. Certain proteins also act as hormones, signaling molecules that regulate various physiological processes. Insulin, for example, regulates blood sugar levels by signaling cells to absorb glucose from the bloodstream.
Storing Genetic Information
The body does not utilize protein to store its primary genetic blueprint. This function is performed by nucleic acids, specifically deoxyribonucleic acid (DNA). DNA molecules are double helices located primarily within cell nuclei, containing all hereditary instructions for development, survival, and reproduction.
Each DNA molecule is composed of a sequence of nucleotide bases—adenine (A), guanine (G), cytosine (C), and thymine (T)—arranged in a specific order. This precise sequence constitutes the genetic code, which dictates the production of all the proteins an organism needs. DNA provides the instructions, and proteins are the products. This highlights a clear division of labor: DNA stores the plan, while proteins execute functions.
Providing Long-Term Energy
While the body can metabolize proteins for energy, this is not their primary role for long-term energy storage. The body prioritizes carbohydrates for immediate energy and relies on lipids (fats) for efficient long-term energy reserves. Lipids are highly efficient at storing energy due to their chemical structure, yielding more than twice the energy per gram compared to proteins or carbohydrates.
Adipose tissue serves as the body’s main energy reservoir, storing substantial energy for extended periods. Using protein for energy is a “last resort” because proteins have many other specialized functions, such as building tissues and catalyzing reactions, which are more valuable. Breaking down proteins for energy sacrifices these important roles, making it an inefficient strategy for sustained energy.