Proteins are large, complex molecules that play a fundamental role in nearly every biological process. They are widely distributed within the body, forming the framework and machinery of cells and tissues. Understanding proteins provides insight into how the body maintains its structure and performs its daily activities.
What Proteins Are and Their Essential Functions
Proteins are intricate molecules constructed from smaller units called amino acids, which link together in long, folded chains. There are 20 different types of amino acids, and their specific sequence dictates each protein’s unique three-dimensional shape and function. This precise structure allows proteins to perform specialized tasks within the human body.
These molecules serve as building blocks, providing structure and support for tissues and organs. For instance, proteins like actin and tubulin contribute to the internal framework of cells and facilitate muscle contraction, enabling movement. Proteins also act as enzymes, accelerating biochemical reactions inside and outside cells, such as those involved in digestion. Messenger proteins, including hormones like growth hormone, transmit signals between cells, tissues, and organs to coordinate bodily processes.
Proteins also function as transporters, binding and carrying atoms and small molecules throughout the body. Hemoglobin, for example, transports oxygen from the lungs to body tissues. Defense proteins, such as antibodies, protect the body by binding to foreign particles like viruses and bacteria, helping to neutralize threats.
Dietary Sources and Daily Protein Needs
The body obtains amino acids for building its proteins from dietary sources. Animal-based proteins, such as meat, poultry, fish, eggs, and dairy products, are complete proteins because they contain all nine essential amino acids the body cannot produce. Plant-based sources, like legumes (beans, peas, lentils), nuts, seeds, whole grains, and soy products (tofu, tempeh), also provide protein. Most plant proteins are incomplete, lacking one or more essential amino acids, but combining different plant foods can provide a complete amino acid profile.
Most adults require approximately 0.8 grams of protein per kilogram of body weight daily to prevent deficiency. For example, a 70-kilogram person would need about 56 grams of protein per day. Individual protein needs vary based on age, activity level, and health conditions. Athletes and highly active individuals, particularly those engaged in strength training or endurance sports, may benefit from a higher intake, ranging from 1.2 to 2.0 grams per kilogram of body weight to support muscle repair and growth. Older adults may also require more protein, around 1.0 to 1.2 grams per kilogram, to help maintain muscle mass and bone strength.